Is 110°C too hot in 96°F ambient temps?

[kre8tive202]

Hello everyone, I live in then peninsula (northern California about 10 miles from San Francisco), its been hot here lately about 90 to 100 degrees. I noticed my car running a little on the hotter side, but it cools when I get to freeway speeds. AC is blowing cold and I definitely have in on. Is this normal?

Sent from my SM-N915F using Tapatalk

 

[daantjie]

Re: Is this too hot?

Perfectly normal under warmer than normal ambient conditions. As long as reading returns to mid range after for example a hill climb on a hot day all good.

 

[gsxr]

Re: Is this too hot?

I'd say that is on the absolute high end of normal when idling around town in ~96F ambients. Your gauge is indicating roughly 108-110°C at which point the electric fans should be on high speed and, with 96F ambients, the mechanical fan clutch should be fully engaged and roaring to 3500rpm.

I would verify the electric fans run on low speed with AC on, and high speed when engine temp is >107°C... and also check that the mechanical fan is engaged & roaring in these conditions. Search the forum for past threads which have covered all this in detail. I'd like to see those temps closer to 100°C (the unmarked line between 80 and 120).

BTW, the fact that it cools down at freeway speeds is a good sign. And check that oil level while you're at it...!

 

[nocfn]

Need some oil asap

 

[kre8tive202]

Thanks bro...I also suspected the mechanical fan but ill check it. my oil level sensor is bad

Sent from my SM-N915F using Tapatalk

 

[duuder]

Mine is reading as high as yours w/ the heat wave we've been getting out east.

 

[195910]

Thats high, a properly functioning cooling system should be maintaining the temp below the 100c mark even at plus 100F. We start to see +100C at more than 45C in at low speed.

 

[samiam44]

I'd say definately check the cooling system. Make sure it's holding pressure and the fan clutch roars. Also as dave noted, the aux fan. Maybe the lead fuse link is fried... not uncommon or needing to be replaced after a few years.


M

 

[Jlaa]

Hello everyone, I live in then peninsula (northern California about 10 miles from San Francisco), its been hot here lately about 90 to 100 degrees. I noticed my car running a little on the hotter side, but it cools when I get to freeway speeds. AC is blowing cold and I definitely have in on. Is this normal?

Sent from my SM-N915F using Tapatalk

Kre8tive, I also live in Northern California (very low humidity), and, in fact, I drove my car this past Sunday, June 18. I distinctly remember being stuck in bumper to bumper traffic for 30 minutes in 97F ambient temperatures on Sir Francis Drake Blvd in Marin, next to San Quentin Prison, on the approach to east-bound Richmond San-Rafael Bridge.

I wish I had taken a picture of my temperature gauge at the time but I did not ---- I was admiring the stability of my car's temperature --- it was midpoint between the 80C and 100C mark - this is with a new thermostat, new radiator, new blue MB coolant, new coolant hoses, new viscous fan clutch (the ACM one), new Purple Ice, and a Cool-Harness-92. Also all the 30A fusible links under the hood are new. My AC was one the whole time. The water pump is original (64K miles).

I think that perhaps that represents the best that the car can get in our Bay Area weather when it is hot.

 

[kre8tive202]

Kre8tive, I also live in Northern California (very low humidity), and, in fact, I drove my car this past Sunday, June 18. I distinctly remember being stuck in bumper to bumper traffic for 30 minutes in 97F ambient temperatures on Sir Francis Drake Blvd in Marin, next to San Quentin Prison, on the approach to east-bound Richmond San-Rafael Bridge.

I wish I had taken a picture of my temperature gauge at the time but I did not ---- I was admiring the stability of my car's temperature --- it was midpoint between the 80C and 100C mark - this is with a new thermostat, new radiator, new blue MB coolant, new coolant hoses, new viscous fan clutch (the ACM one), new Purple Ice, and a Cool-Harness-92. Also all the 30A fusible links under the hood are new. My AC was one the whole time. The water pump is original (64K miles).

I think that perhaps that represents the best that the car can get in our Bay Area weather when it is hot.

I am jealous buddy

Sent from my SM-N915F using Tapatalk

 

[jhodg5ck]

I use the "cooler harness" on all of my cars here..customers as well. Only diff being I just buy the 1.1kohm resistor in bulk and wedge it b/w the connector and the temp sensor pins. You can cut the tangs short so it tucks up and out of sight. I also have 900kohm but they kick @ 85-86 degrees...I save these for some of the older cars that Rarely get much above 80.

I always felt waiting till 105 seemed a bit excessive...

Jono

 

[gsxr]

Just a heads-up on the "cool harness" resistor trick: In general, once the fans kick on, they may never turn off until the ignition is turned off. And the fans are not particularly quiet. I like Jono's idea of wedging the resistor in so you can try it out, and remove as desired. The only down side to this trick for people who live in places that have 4 seasons, is the auto fan speed starts blowing cold air with the heater on, because the HVAC thinks the engine is warmer than it is. Took me a while to figure that out!

 

[kre8tive202]

Just a heads-up on the "cool harness" resistor trick...

where do I get a cool harness

Sent from my SM-N915F using Tapatalk

 

[8899]

where do I get a cool harness

http://www.k6jrf.com/MB_S500.html

However, if I were you...I would focus your efforts first on getting an operational fan-clutch installed.

 

[Jlaa]

You can get it here but I use it mainly for an extra ma gin of error on an otherwise healthy cooling system. If the cooling system is marginal then please please dont use it to mask a bigger problem.... just my 2 cents .... I installed it only after I made sure my cooling system was healthy...

https://www.k6jrf.com/MB_S500.html

 

[gsxr]

Greg and Jlaa are correct. Don't use the resistor to mask a different problem. The main reason for the upgrade is to improve AC performance in hot climates at low vehicle/engine speeds, where the mechanical clutch isn't moving enough air due to low RPM.

The resistor mod has been sold to many people who expect, or at least want, their engine to always run at 85-90C... but IMO this is an unreasonable expectation outside best-case scenarios.

 

[kre8tive202]

Greg and Jlaa are correct. Don't use the resistor to mask a different problem. The main reason for the upgrade is to improve AC performance in hot climates at low vehicle/engine speeds, where the mechanical clutch isn't moving enough air due to low RPM.

The resistor mod has been sold to many people who expect, or at least want, their engine to always run at 85-90C... but IMO this is an unreasonable expectation outside best-case scenarios.

i agree I wont.

Sent from my SM-N915F using Tapatalk

 

[Mejnoon]

I live in the central valley, it was nearly 110f all of last week and my car ran a little over 100* most of the time at highway speed. Idled close to that point if let it sit for a few minutes after a highway trip. I replaced my aux fan recently and I think the new one isn't working quite as efficiently as the old; its a behr, but it just doesn't sound the same and the car seems to run a little hotter. My mechanic says its fine, but I kinda want to swap it out again.

 

[kre8tive202]

I live in the central valley, it was nearly 110f all of last week and my car ran a little over 100* most of the time at highway speed.

I am planning to do a system flush and thermostate change

Sent from my SM-N915F using Tapatalk

 

[gsxr]

I live in the central valley, it was nearly 110f all of last week and my car ran a little over 100* most of the time at highway speed.

That all sounds perfectly normal (for high ambient temps).

I replaced my aux fan recently and I think the new one isn't working quite as efficiently as the old; its a behr, but it just doesn't sound the same and the car seems to run a little hotter. My mechanic says its fine, but I kinda want to swap it out again.

The auxiliary fan provides little cooling power, especially with the fans on low speed, or the car moving >30mph. The electric fans are more for condenser airflow than radiator/engine cooling, IMO. If the auxiliary electric fans are working, replacing them with different ones will most likely only lighten your wallet... it's a ~5 hour job as the radiator has to be removed to replace the electric fans.

 

[msq]

Are the electric/auxiliary fans always supposed to be on if you have A/C on?

I think mine only go on "high" when the car gets ~100 - 105C

If the electric/auxiliary fans always supposed to be on if you have A/C on and they are not what is typically the cause of that?
My electric/auxiliary fans are clearly working when the car goes up to ~100 - 105C, and it cools the car down to ~90C right away, but I am not sure they are working when A/C is turned on since the car should not have gotten that hot when I was idling, with A/C on and it was 57F outside. I don't have the car with me today so I can't check, but I know I had the A/C on the other day and it was only 57F outside and I let the car idled for 15 mins and the temp when up to ~100 - 105C so I am not sure the electric/auxiliary fans were on when the A/C was on. I will check when I am back to my car tomorrow.

In any case is are the electric/auxiliary fans always supposed to be on if you have A/C on and if so and they are not, what is typical root cause?

 

[gerryvz]

The fans are two-stage.

Stage 1 (low) is always when A/C is on. GSXR edit below.

Stage 1 (low) is on when A/C low-side refrigerant pressures exceed 16 bar; which is most of the time with AC on in hot weather.

Stage 2 (high) is on at ~107C or higher. It’s triggered by coolant temps.

I found that with a not-perfect fan clutch, when I lived in hot and humid Texas, that I would regularly hit 105-115C temps at high speeds (65-95 MPH) in high (90+F) ambient temperatures in high Houston humidity.

With same fan clutch, I am hitting 95-105C temps at freeway speeds in less-humid Maryland. Today I drove nearly 70 miles from my house to Dulles Airport in 84-86F ambient temps with A/C on. Never saw above 105C. Usually around 100C. It doesn’t bother me to be running 100C+ in high ambient temps with A/C on.

If A/C is not on, expect 3 degrees (perhaps as much as five degrees) reduction in indicated temp.

In Maryland temps up to 80-85F outside, I never see more than 100C indicated, unless idling for a long time at a stoplight. Temps will go down immediately after starting from a stoplight.

My experience is that M119 and M104 cooling systems are very sensitive to both ambient temps and especially ambient humidity levels. The less humid outside, the cooler things will run at a given/equivalent ambient temperature. When I lived in. Sry moderate Portland OR, I don’t think I ever even saw 100C indicated unless a very long stoplight on a hot July or August day.

I have a brand new factory fan clutch that I hope to install soon to compare.

Cheers,
Gerry

 

[8899]

If the electric/auxiliary fans always supposed to be on if you have A/C on and they are not what is typically the cause of that?
My electric/auxiliary fans are clearly working when the car goes up to ~100 - 105C, and it cools the car down to ~90C right away, but I am not sure they are working when A/C is turned on since the car should not have gotten that hot when I was idling, with A/C on and it was 57F outside.

I had this problem. Aux fans not working with A/C on low-speed, but would work on high-speed when the temp got to around 103*C. Problem was traced to a blown fuse.

 

[msq]

The fans are two-stage.

Stage 1 (low) is always on if the A/C is on.

Stage 2 (high) is on at ~105C or higher. It’s triggered by coolant temps.
......
I have a brand new factory fan clutch that I hope to install soon to compare.

Thanks Gerry. Any suggestions on where to buy a factory fan clutch (if it turns out I need one). I have read thread on here where someone was really happy with FCP/ACM one but I also read a review on the FCP site that the ACM ones from China are not as thick and require smaller bolt: "IMPORTANT This clutch is 2" thick. The original is 2 1/2". If you try and install using the original center bolt you will have lots of axial play, be scratching your head and have to do it twice. I don't know if a shorter bolt is available, I'm going to cut 1/2" off mine". When I get my car back I will make sure the fan clutch is working but I need to make sure if electrical/auxiliary fan is doing Stage 1 turn on with A/C.

 

[msq]

I had this problem. Aux fans not working with A/C on low-speed, but would work on high-speed when the temp got to around 103*C. Problem was traced to a blown fuse.

Thanks, this is also quite helpful.
When I get my car back I will have to check if it the electrical/auxiliary fan goes on when A/C is on, if not I'll have to figure out which fuse number it is that controls stage 1 for A/C fan.

 

[gsxr]

msq, if your car is facelift, the aux fan fuses are located on the cube relays. You have to remove the cover that hides the relays, behind the normal fuse area.

 

[Jlaa]

Thanks Gerry. Any suggestions on where to buy a factory fan clutch (if it turns out I need one). I have read thread on here where someone was really happy with FCP/ACM one but I also read a review on the FCP site that the ACM ones from China are not as thick and require smaller bolt: "IMPORTANT This clutch is 2" thick. The original is 2 1/2". If you try and install using the original center bolt you will have lots of axial play, be scratching your head and have to do it twice. I don't know if a shorter bolt is available, I'm going to cut 1/2" off mine". When I get my car back I will make sure the fan clutch is working but I need to make sure if electrical/auxiliary fan is doing Stage 1 turn on with A/C.

The shorter bolt that works with the ACM fan clutch is M10x50mm 000912-010222 from MB.

 

[msq]

msq, if your car is facelift, the aux fan fuses are located on the cube relays. You have to remove the cover that hides the relays, behind the normal fuse area.

Thanks @gsxr !
It is a facelift....the car is actually a '94 MY but was delivered in Dec '93 so (as you know) in Europe they list Year as date of first reg. so its registered as '93 here in US (original Bill of Sale called out '94 but I didn't want to get into it with DMV trying to reconcile - they were as difficult as you can imagine already just registering a Euro car in the first place)
I won't have my car back until late this evening or tomorrow so I have been looking on-line (to no avail) for fuse box card for Euro '94 E500. I found some that say "USA" model (enclosed example - not even sure this is a '94 example if there were in fact differences), and I am no sure if Euro models have same fuse box and could not find Euro fuse box data card example to verify. The thing that I don't understand is, if the enclosed card is correct for my car (i.e. if the US & Euro one is the same) and it lists only one entry for auxiliary fan ("D"), why would the auxiliary fan work at Stage 2 (i.e. when car gets up to 103C) and not at Stage 1 (A/C turned on) if fuse was bad?
Not having the car with me now (otherwise I would just go check/try) is it safe to assume removing the cover that hides the relays does not require anything special (tool or trick)?

 

[gerryvz]

Thanks Gerry. Any suggestions on where to buy a factory fan clutch (if it turns out I need one).

Your best bet is going to be www.mboemparts.com with the code 500EPROMO for free shipping. That will get you a factory part. Enjoy the price !!

 

[msq]

Your best bet is going to be www.mboemparts.com with the code 500EPROMO for free shipping. That will get you a factory part. Enjoy the price !!

Thanks Gerry! (will check if the one on the car is still good and if not will use this)

 

[gsxr]

Thanks @gsxr !
It is a facelift.... The thing that I don't understand is, if the enclosed card is correct for my car (i.e. if the US & Euro one is the same) and it lists only one entry for auxiliary fan ("D"), why would the auxiliary fan work at Stage 2 (i.e. when car gets up to 103C) and not at Stage 1 (A/C turned on) if fuse was bad?

The facelift cars have 2 separate fuses, one for low speed, one for high speed. Pre-facelift have a single fuse for both high & low speeds. You need to check if the low-speed fuse is bad, on the cube relay. If it's a 15A, replace it with a 20A (this is Klink-approved, and documented previously on the forum). If the 20A fuse blows, you have other issues. Also, if the fuse is good, you may have the in-famous issue with the wire degrading at the resistor behind the driver headlight (also well documented on the forum).

Note that if it's not warm out, and/or your AC isn't fully charged, and/or the switch is bad... the low speed fans may not run if the relay isn't getting a signal to turn on. This can be tested by shorting together the 2 wires at the red pressure switch behind / below the driver headlight. Search the forum for details, it's been covered several times, complete with photos.

 

[tomer]

My aux fans have never come on with the AC on in the entire time I have owned the car!! They do come on high when the temp gets over the 100 degree mark.
A google search led me to a reference to an "Aux wiring harness" which runs along the frame rail (not sure where) and is subject to the wire insulation cracking/falling off and can lead to the blown relay fuse. Can anyone confirm this? If so, I best check my fuse and this harness!! thx

 

[gsxr]

Required reading, all the way to the end:

https://www.500eboard.co/forums/index.php?threads/auxiliary-electric-twin-cooling-fan-troubles.5135/

 

[msq]

Ok I got my car back tonight (clearbra application.....there is no kit for this car and the guy did an incredible job, looks like there was a premade kit).

So Auxiliary Fan Stage 1 (i.e. when A/C is turned on) does not work, but Auxiliary fan Stage 2 (car heats up to ~103C) does work.

I opened the fuse box and the "fuse box card" on my Euro model is different than US "fuse box" card. As you can see (and as @gsxr points out) the auxiliary fan fuse is in a separate box outside the main fuse box. The interesting thing in my car the aux fan is in a separate box and "fuse box card" specifies that (see bottom of my card in pic "outside fuse box:" auxiliary fan) and the US one the auxiliary fan is in position "D" (assuming the example fuse data card that specifies US is in fact a US one for E500E's - which the site I got it from said it was).

If you see the enclosed picture from my car of the "outside fuse box" you can see that one of the two fuses is missing. Since the "outside the fuse box" on my car is for blower motor, seat heating front, telephone, auxiliary fan.....I am hoping it's the auxiliary fan one that is missing. I have no idea why one is missing. Since there are two fuses and there is no "telephone" in the car, I am wondering if one of the two of these fuses were for "blower motor, seat heating front" and the other one is for "telephone, auxiliary fan" or is it the case that both fuses are needed to support all 4?

Also, I am curious why in the main fuse box, fuse 11 is missing and everything is working (except aux fan Stage 1, when AC is turned on). Fuse 11 is anti-theft system and the fuse card has two fuses for that 11 & 12. I believe my antitheft system is working and the infrared lock/unlock work (assuming they are part of that - which may be bad assumption).

UPDATE:
p.s. I put a 16A fuse in the one that was empty in "outside fuse box" compartment and ran car for 15-20 mins until car reached maybe 85+C and turned AC on and Stage 1 auxiliary fan did not come on. I read the full thread below that @gsxr mentioned
https://www.500eboard.co/forums/index.php?threads/auxiliary-electric-twin-cooling-fan-troubles.5135/
...so I am wondering since the ambient temperature is on ~50F, even with the A/C on and engine ~85C, would the aux fan Stage 1 go one. I have no way to measure pressure in the A/C system right now so I have no data on that.

 

[gsxr]

msq, you will need to short out the leads from the red pressure switch to test the low speed fans. No need to run the AC at all.

You MUST remove the cover over the relay box to locate the 2 colored cube relays for the fans, and check the fuse on the low-speed relay. The fuse plugs into the relay itself, the fuses are not separate like all other fuses. See attached PDF and photos. The orange relay is for the high speed, low speed may be either green or blue. Ignore what the fuse box card says.

Fuse 11, per the ETM, appears to be only for the alarm system - which is separate from the central locking. The single 30A strip fuse located outside the main fuse box is for the HVAC blower underneath the wiper. Pre-facelift cars had a second 30A strip fuse for the twin auxiliary fans, facelift cars do not have this, as described previously.

 

[msq]

Thanks @gsxr.
As recommended:

- I ignored what the fuse box card says

- Opened the relay box

- There is only one "orange" relay (not two on my car) (p/n: 0015429719 - same as the one in your picture above) and one "blue" relay Hella part # 4RA007077-03

- The orange relay has a 40 amp fuse and I can't tell if that 40 amp fuse is burned out, it looks like it is in tact and ok as you can see from picture (no broken connection - although pic is blurry - could not make iPhone focus that close up), and, not sure if this matters (I don't think it should) the orange 40 amp fuse in your pic looks like it has a clear film on top where mine does not (that should not have anything to do w/electrical circuit being complete). I can change fuse anyway.

- In the relay/fuse box - next to the orange relay p/n: 0015429719 is a blue relay 12V - 15amp fuse and it has Hella part # 4RA007077-03 stamped on it and it also has 0025420119 printed on it. As you can see from the picture the 15A fuse is cooked. When I look up this 4RA007077-03 on the web it says "auxiliary fan" relay. Is this the one it is ok to replace with 20amp fuse or not. I saw @Klink post in the post about troubleshooting aux fans that said (for US cars I assume since it's the D position in fuse box) "For all 107, 123, 126, and 124, If you have a red ceramic 16 amp auxiliary fan fuse in your fuse box [fuse D on the 124], replace it with a blue 25A fuse. It will stop chronically cracking putting thousands of dollars of your refrigeration system at risk. If you develop an actual high current consumption situation, it will burn open as it should and protect the wiring. [Note: This applies to non-V8 models of the 124 chassis. The 400E/500E do not use fuse D as the power feed for the twin auxiliary fans.]" ....but should I assume that is not the same as the 15A in my aux fan relay (I would think it's not, but since US cars have aux fan fuse in "D" position and on my car fuse box card for aux fan says "outside fuse box", I just want to make sure that I am not supposed to replace this burnt 15A fuse in the relay with a stronger one?

- Separate from relay/fuse question: the two empty fuse slots in post #34 above (slot 11 and the one that is outside the fuse box) should they have fuses in them?

- You can see pic below of my fuse/relay box and the orange relay p/n: 0015429719 was in the empty slot next to the green one and the blue relay 4RA007077-03 was in the empty slot to the right of the orange one (when looking down on it from driver side of car)

- I don't know if I'll have trouble shorting the leads from the red pressure switch (or even locating it), but I guess I should start with replacing the burnt 15A fuse in the blue relay 4RA007077-03 and I think I'll replace the 40A one on the orange relay 0015429719, even though it does not look burned out.

 

[gsxr]

Yup, you found 'em! Blue relay is for low speed fans, orange is for high speed. Replace the cooked fuse with either a new 15A, or a 20A (maximum). It may have been in a different thread where he referenced the blade-style fuses.

Klink's comments about 16A red ceramic and 25A blue ceramic fuses are for non-V8 models, so it doesn't apply to E500E.

If everything is working normally in your car, I wouldn't worry about the "missing" fuses.

Yes, replace the bad fuse first, if your low speed fans start working normally again, there's no need to fiddle with the red pressure switch.

 

[tomer]

For my facelift 94, I have one orange relay with a 40 amp fuse (presume this is high speed relay) and a green 30 amp fuse relay...

If the green relay is for low speed operation, is it supposed to be a 30 amp fused relay, or did the previous owner perhaps replace this with the wrong relay?? thx

 

[msq]

@gsxr ..... that's great, will do. This probably explains why the low speed fan was not turning on. Very helpful. Thanks much.

p.s. just as I was about to post this, after replacing burned out 15A fuse in aux fan stage 1 relay; I let the car run for ~30 mins with AC on full force and the stage 1 fans still did not come on at any point. The temp got up to what you can see in the pic below (question - is that first hash mark after/above 90C or is it some other temp) and no stage 1 fan operation.
I saw your post @gsxr, post #3 in https://www.500eboard.co/forums/index.php?threads/auxiliary-electric-twin-cooling-fan-troubles.5135/
regarding stage 1 aux fan that says "The electric fans trigger on low speed based on refrigerant pressure, not engine temp. If it wasn't warm enough outside, they may not turn on. However, they will usually run if it's above ~80°F ambient temp with AC on"

...it's only 60F today when I let it run for 30 mins w/AC on full blast after replacing burnt fuse and still no stage 1 fan, but I am now wondering if it's because it is simply too cool outside. Could it be that its too cool outside and even with engine temp what it is in pic below that stage 1 aux fan will not come one? (After the cars cools down, I'll check the new fuse to make sure its not fried, perhaps indicating a short. I am hoping not to have to try to short the leads on the red pressure switch, since I am not even sure I will know where to find it and I don't want to screw something up trying to short it, but maybe its not that hard?)

 

[Jlaa]

@gsxr

"The electric fans trigger on low speed based on refrigerant pressure, not engine temp. If it wasn't warm enough outside, they may not turn on. However, they will usually run if it's above ~80°F ambient temp with AC on"

...it's only 60F today when I let it run for 30 mins w/AC on full blast after replacing burnt fuse and still no stage 1 fan, but I am now wondering if it's because it is simply too cool outside. ...

what if you pointed a hair dryer directly at the front of the car during the test? A hair dryer definitely spits out air way above 80F.

 

[gerryvz]

That photo is only about 103C, 105C max. Likely not high enough to trigger the Stage 2 fan. People freak out about it, but this level of indicated temp is NOT abnormal on a reasonably hot day with high ambients and humidity, and you'll also see it climb like this on a modest day at a stoplight.

The un-numbered hash mark is 100C.

 

[gerryvz]

what if you pointed a hair dryer directly at the front of the car during the test? A hair dryer definitely spits out air way above 80F.

Just be careful if you use a hair dryer, not to accidentally crack or chip your headlight lens.....

 

[msq]

Thanks Gerry. I know the stage 2 aux fans work when the car gets hot enough. After finding the blown fuse in Hella part # 4RA007077-03 stage 1 aux fan and replacing it....I figured stage 1 aux fan would trigger if I had AC on full blast and let the car run for 30 mins. It did not. Then I remembers @gsxr post that stage 1 gets triggered based on refrigeration pressure and that if it was not warm enough outside (say 80F) maybe that is why.
So now I am more sure if its that it just is not warm enough out. I am not overly worried about 103C but assumed stage 1 would kick on (if AC was on) before that (even though it sounds like it gets triggered by something else).

 

[gsxr]

msq, first double-check and make sure the new fuse isn't blown again... if so, something is shorted out.

Next, you'll need to short the wires at the red switch and try to force the fans on low speed. It's not difficult and the risk of messing anything up is pretty small. If the fans turn on low speed, either the ambient temps were too low, and/or the refrigerant is a bit low on charge. (Did you get ice cold air out the vents with the temp wheel on minimum? At 60F outside, it should have been near 40F out the vents.)

Your engine temps are higher than normal partially because the low speed fans are not running. However you can't really troubleshoot this until you get the low speed fans confirmed to be working. There's a faint possibility your fan clutch is not engaging as much as it should, but first get the electric fans on with the AC and see what the engine temp is.

BTW - Gerry is correct, the indicated temp on your gauge is in the 103-105°C ballpark (assuming the gauge is accurate), which is below the 107°C engagement temp for the high speed fans. Nothing to be concerned about, yet.

 

[msq]

@gsxr, will do...will check fuse to see if its fried again, indicating a short. If not then I guess next two steps are shorting the low speed red switch. I have zero confidence I'll locate it - is there a picture? I saw the below pic from from @M104-AMG post #24 https://www.500eboard.co/forums/index.php?threads/auxiliary-electric-twin-cooling-fan-troubles.5135/
I have no perspective of where that is (looks near one of the sidewalls) and is it safe to assume that its the one in the picture below with the blue box drawn around it that says aux fan jumper. If it is, is it obvious when looking at the connector where to stick two and of a metal paper clip in?

RE: corroded connector possibility, I am concerned about taking out the driver side headlight, if that is where the connection can fray/corrode, since I never have taken headlight out on this model car and they are NLA and I also don't want to potentially break even the great plastic housing around it. I wish there were a Haynes manual for the E500E (I know there is for other 124 models).

Lastly fan clutch on mechanical may also be weak (separate issue), Jonathan had me do "magazine test" i.e. with car running and warned up to temp I folded a magazine and could stop the primary mechanical fan.

I'll report back after checking if new fuse is cooked.

 

[msq]

For my facelift 94, I have one orange relay with a 40 amp fuse (presume this is high speed relay) and a green 30 amp fuse relay...

If the green relay is for low speed operation, is it supposed to be a 30 amp fused relay, or did the previous owner perhaps replace this with the wrong relay?? thx
View attachment 82570

Thomas,
The relay closest to the firewall is blue and on my car is Hella part # 4RA007077-03 it is the stage 1 aux fan relay w/fuse in it. My relay set-up looks like yours i.e. silver, green orange, blue (assuming your last one closest to the firewall is blue on yours - not green - I can not tell from your picture, maybe it is green on yours, not blue?). In any case just pull it (the one closest to firewall), look at the fuse to see if its fried and look at the part number on the relay and check it out on the web and you will see what it is.

--------

@gsxr thanks again for alI the ideas and links. I will go back to my car today and find out if new fuse is fried. In case fuse is fried, I looked up how to pull drivers side headlight, and its looks not to hard. It wasn't clear of I had to remove the headlight wiper to do so, if so that's the only hassle. My big concern is breaking it since euro headlights are NLA, but I'll just have to be extra careful

 

[gsxr]

The low speed fan would normally have a blue relay. Think I've seen some with either green/30A or orange/40A for the high speed fans. Never seen green/30A for low and orange/40A for high, sounds like someone changed it... and I would NOT recommend a 30A fuse for the low speed fan circuit.

msq, to access the red switch for testing, there's no need to pull the headlight. You will want to remove the air intake tube (easy) but otherwise it isn't hard to access. Now, if you end up having to get to the resistor... that's a different story. Removing the headlight would make access to that area much easier. Think I've done it with the headlight in place before but it wasn't fun.

 

[msq]

@gsxr thank you.
Yes RE: headlight I was thinking about access to resistor. If I have to go there maybe I bring it to local indie who is great with older MB's & BMWs (he's been at it for 30 years and is really good).
I will first try red switch jumping depending if fuse is fried again and/or the fan does not come on when left running for 25 mins.

will report back.

 

[gerryvz]

With same fan clutch, I am hitting 95-105C temps at freeway speeds in less-humid Maryland. Today I drove nearly 70 miles from my house to Dulles Airport in 84-86F ambient temps with A/C on. Never saw above 105C. Usually around 100C. It doesn’t bother me to be running 100C+ in high ambient temps with A/C on.

...it's only 60F today when I let it run for 30 mins w/AC on full blast after replacing burnt fuse and still no stage 1 fan, but I am now wondering if it's because it is simply too cool outside. Could it be that its too cool outside and even with engine temp what it is in pic below that stage 1 aux fan will not come one?

I drove the ~65 miles back home from Dulles this morning. Ambient temps were 68-72F along the way. A couple of small stretches of stop and go traffic, but most of the trip I was moving along fine at speeds up to 90 MPH. The highest temp I saw on the way home was 100C indicated.

This is a photo on US-50, in Annapolis, just before the bridge over the Severn River. I was moving at a good clip, ambient 71F. Indicated temp was 91-92C with A/C on (center button pressed).

 

[msq]

Ok so the new 15A fuse in the blue relay (relay part #: Hella 4RA007077-03) is not fried/burnt out.
Is this 1st picture enclosed below is from my car) the red switch (pressure switch?) for the aux fan? The part numbers on it are 004820680120 and PS1053-001 (funny when I search for them on the web to verify part I come up empty).

I know this is a dumb question - but I don't know the answer - If this red switch is the right part, it looks like a switch (hence the name "switch ...duh....not a male or female connector), but I am not sure I did not pull it. In order to jump/short where does the paper clip go? Do I short/jump it somewhere else i.e. are there tails on the red connector like 3rd picture below and do I locate the two tails of the red switch and jump/short those?

I tried not to waste anyone's time by first looking online to see picture but no luck. I did find 2nd picture below on peach parts, but that is a RHD Japanese1989 260E and it looks like you just short/jumper the two white/clear tails that connect to the red switch on that car. I would not be asking so many questions but I don't want to inadvertently fry something. I also did read this twice in advance but the pic is from an M104:
https://www.500eboard.co/forums/index.php?threads/auxiliary-electric-twin-cooling-fan-troubles.5135/

So I guess my questions are:
- where or how do I jump/short the red switch?
- on the E500E does the red switch have two tails somewhere (like pic 3 below) and is that what gets shorted?