Auxiliary (electric twin cooling) Fan Troubles - Resistor wiring problem

[gsxr]

If the system lost a LOT of coolant, the leak is more likely to be lower down vertically. If the leak is near the top of the system, you can usually see the white residue from the leak point. This is another reason to use the G-05 coolant, it leaves a nice white trail to help you find leaks.

Related anecdote: My buddy's E420 has been slowly losing coolant (like, a pint every few months) and the pressure tester located the leak... it was the radiator itself, between the core and the side tank, the seal was leaking. It was very slight and only happened under 10-15psi which makes sense, in his case.

 

[lil_dz33]

Im hoping its not an internal leak. I just sold my 190E and don't have a second car at the moment!

I am doing a coolant pressure test tomorrow and will report back!

 

[Klink]

The tech information is all WELL covered above. I'm just offering this encouragement:

Remain calm, and don't loose sleep. Other than ONE 400E that was driven on the interstate, pretty much flat out until it stopped after a cinder block holed the radiator, I've NEVER seen a M119 with an internal coolant breach, even after serious overheating, which yours hasn't experienced. At least not today.

 

[lil_dz33]

The tech information is all WELL covered above. I'm just offering this encouragement:

Remain calm, and don't loose sleep. Other than ONE 400E that was driven on the interstate, pretty much flat out until it stopped after a cinder block holed the radiator, I've NEVER seen a M119 with an internal coolant breach, even after serious overheating, which yours hasn't experienced. At least not today.

Thank you for the encouragement, Klink!

after filling the car last week with water, my dad and I performed the radiator pressure test today. Between now and then, I've checked the coolant and it hasnt lost any.. It hasn't overheated.

We got the system to about 6PSI and it maintained pressure for a solid 10-15 minutes. We couldnt find any leaks, inside or outside the car. My dad speculates it was just an air pocket. Will just have to keep on driving her and see.... Any thoughts? Or just keep driving the old girl?

 

[Klink]

Thank you for the encouragement, Klink!

after filling the car last week with water, my dad and I performed the radiator pressure test today. Between now and then, I've checked the coolant and it hasnt lost any.. It hasn't overheated.

We got the system to about 6PSI and it maintained pressure for a solid 10-15 minutes. We couldnt find any leaks, inside or outside the car. My dad speculates it was just an air pocket. Will just have to keep on driving her and see.... Any thoughts? Or just keep driving the old girl?

So far so good. If you have not already done so, replace the coolant tank cap. A leaking coolant pressure cap can produce exactly the syndrome you describe. That is to say, everything seems fine on the highway then at the exit it burps coolant.
I'd do that next and then keep an eye on things.

all the best

 

[clarkz71]

We got the system to about 6PSI and it maintained pressure for a solid 10-15 minutes. We couldnt find any leaks, inside or outside the car.

Slight problem.

You need to pressurize the system to "at least" 15 psi

The expansion tank cap is rated for 1.4 bar, which is 20 psi

Surprised you missed that Klink

 

[lil_dz33]

Slight problem.

You need to pressurize the system to "at least" 15 psi

The expansion tank cap is rated for 1.4 bar, which is 20 psi

Surprised you missed that Klink

I see, I was worried I was going to pop the head gasket applying too much pressure. I'll have at it again tonight! Thank you!

 

[gsxr]

+1 with Clark. Pressurize the system to 15psi. 6psi isn't enough... minor leaks may not appear until you get around the 12-15psi range. Also verify the coolant level is the same after the test, as it was before... if not, the coolant went somewhere. Check the washer fluid tank, that's a common place for it to end up when the washer t-stat O-rings fail.

You can avoid air pockets by filling the block via the upper radiator hose. When the block is fully drained, you can get about 5 quarts in via the hose, and another ~4 in to the reservoir tank, assuming the radiator is empty. It will usually burp and take another pint or two after reaching operating temp. Generally takes around 10 quarts total (which, you may note, is far less than the factory spec... I believe the FSM specs are wrong for the 034/036, and actual system capacity is around 12 quarts total, not 16. But that's probably a different discussion.)

 

[lil_dz33]

So far so good. If you have not already done so, replace the coolant tank cap. A leaking coolant pressure cap can produce exactly the syndrome you describe. That is to say, everything seems fine on the highway then at the exit it burps coolant.
I'd do that next and then keep an eye on things.

all the best

Thank you for the help Klink! I replaced the cap along with the expansion tank approximately 6 months-ish ago. It looks to be in good condition and I don't see any coolant/dampness around the cap after driving.

 

[gsxr]

Just checking... is the new cap an OE/OEM Reutter cap?

If the cap is leaking, it would allow the coolant to exit the overflow hose, to the tank hidden in the fender... you may never see any sign of the leakage.

 

[clarkz71]

Current part # is 124-500-0406

Should look like this.

 

[Klink]

Slight problem.

You need to pressurize the system to "at least" 15 psi

The expansion tank cap is rated for 1.4 bar, which is 20 psi

Surprised you missed that Klink

Yeah, good call Vader. Read it too quick and answered on I phone (tiny print for these old eyes). Saw the "6" thought "16" like a dumbass. As always here, the poster is getting a torrent of great info. Thanks for catching that Clark.
You too, gsxr.

 

[lil_dz33]

Hey Everybody!

My radiator cap doesnt have the Mercedes Star on it, (It says REUTTER on the underside plastic? valve). I believe it to be OE.

I can't tell what to make of the situation. I ran a radiator pressure test again, This time I took it up to 15 PSI, It held pressure and we found no leaks.

I test drove the car around town, It stayed consistently around 90-100.

It wasn't until I got on the freeway it reached above 100. I exited the freeway and it climbed slightly (105-107?) and stayed there until I got home.

I'll try driving it a longer distance and see if it continues to climb. I'm worried it might.

 

[gsxr]

That still sounds higher than normal. Have you replaced any parts yet? What is the coolant level in the plastic tank? If you are running the AC, have you confirmed the electric fans are running when the AC is on?

 

[lil_dz33]

Heya Dave!

The only things I've recently replaced were the following:

Waterpump
T-Stat (with housing)
lower radiator hose
Water Pump Elbow Hose
Fan Clutch

Fluid level is normal after a drive when the car gets "warm"

I am not running the AC. Don't want to run the risk of the car getting hotter than it already is

 

[gsxr]

Just curious, what brand t-stat and what brand fan clutch? Have you confirmed the clutch is working per the roar test?
http://www.500eboard.com/forums/showwiki.php?title=Viscous_Fan_Clutch

Engine temps at 105C without the AC running seems abnormally high to me. If you turn the heater on max, do you get hot air from the vents?

 

[lil_dz33]

The Fan Clutch is an ACM unit and appears to be functioning (tested using the Roar test).

The T stat is a Wahler unit.

My heater does not work, hasn't worked for the past year? Not too sure if the auxiliary WP is kicking on...

 

[gsxr]

My heater does not work, hasn't worked for the past year? Not too sure if the auxiliary WP is kicking on...

That is fishy. The aux pump doesn't need to work to get heat, and the HVAC system default is max heat. Have you confirmed that there is liquid in the upper radiator hose? You can feel it when squeezing the hose on a cold engine. Very weird to not have a working heater.

 

[lil_dz33]

Now I'm confused. I'm not certain there is liquid in the upper rad hose when cold (there definitely is liquid when hot, it gets rock solid)

If I squeeze the upper radiator hose, I can hear water "swish" in the expansion tank....

 

[emerydc8]

Are you getting a code 31 on the climate control module (socket 16) (bad heater valve)?

 

[gsxr]

The upper hose gets firm when hot due to pressure, but there's no way to tell if there is liquid in there when hot, because you can't squeeze it enough.

When cold, you should be able to feel liquid inside. Think of the difference between a balloon filled with water, vs filled with air. I just went out and checked two of my cars to make sure I wasn't hallucinating the effect. There really shouldn't be any "swish" noise at the expansion tank though. It should just push liquid in & out, almost silently, at least when the cap is in place.

 

[Klink]

Those heater valves do sometimes mechanically stick closed. No codes, just no flow. The valves are powered closed, so if you disconnect the plug from it you should have unobstructed flow through the heater.

 

[Glen]

Those heater valves do sometimes mechanically stick closed. No codes, just no flow. The valves are powered closed, so if you disconnect the plug from it you should have unobstructed flow through the heater.

That's how mine failed in the '95 wagon. No heat is no bueno. I took it apart and cleaned it and got a few more months out of it before it failed again. New valve is a little spendy but worth it.

 

[lil_dz33]

Well, I can 1000% confirm that there is coolant in my upper radiator hose. I took it off the top of my radiator and there was plenty of it in there.

The heater hose going from the Aux water pump to the cylinder head was kinked due to a previous band-aid repair. I did my best to try and cut it to correct length but it's still kinked. I'm going to have to see if I can find the correct molded hose and hope that fixes the heater problem. That still wont explain why i'm loosing coolant...

I just picked up a new car a week ago. So there's no rush in getting this diagnosed and fixed correctly. I appreciate the loads of information and help I'm getting, everyone!

 

[gerryvz]

There are two different types of valves used in the W124s. All of the E500Es use the "early" type valve, which is actually a separate valve & aux water pump. The later style is a combined valve+pump.

I did a HOW-TO on this some time back. The replacement of the E500E separate components is essentially the same, though because they are separate units one is a bit more difficult to get at.

Cheers,
Gerry

 

[richardhilton590]

This has been my problem too for the past few days. I've been reading for tips or any help that might work on my current situation. I appreciate all the replies here as well.

 

[DW SD]

Gang,
My 1992 500E. My low speed and high speed Aux fans are not working.
I removed the coolant connector while the engine was running and high speed did not engage. I also cycled my AC on full cold in 80F weather for fifteen minutes in the heat and never saw low speed engage. In fact, I'm pretty sure the high pressure compressor cutout kicked in because for a while it wasn't blowing cold air.

Where are the strip fuses located? If those are good, I'll be looking at the high / low relay. Would that be appropriate troubleshooting steps?

Thank you,

Doug

 

[gsxr]

Doug, I assume that is a typo, as a 1995 500E does not exist.

For a 1994-1995 model, the fuses will be inserted in the individual relays, with NO external strip fuse. See Clark's photos in post #9 above.

For 1992-1993 models, there are two different external strip fuse holders. You want the one behind the brake booster NOT the one at the strut mount.

 

[gerryvz]

Dave is correct - for the low and high speed aux fans on late cars, they are controlled by relays with spade fuses embedded in the outside of the relays.

What is the refrigerant pressure in your A/C system? If the compressor is conking out, it may be because you don't have adequate pressure in the system, and/or there is oil on the compressor pulley that is causing belt slippage, which the system can sense and cut off the compressor.

Has your A/C system been working up to now? R134a systems run at pretty high systems pressures, so it's important to get this checked out.

 

[mwaldron]

Do not forget that pesky resister behind the headlight bucket, my connections were such that when the wire terminal corroded it was on the side that the power for high speed is jumpered from so terminal failure lead to a total loss of fans, not just low speed.

Also although the resister was still good it didn't survive the R/R so have a replacement handy once you go to all the trouble to get to it, another thing you won't have to address for 20+ years.

Mark

 

[DW SD]

Sorry. 1992, typo. I looked at the fan fuse and connectors to it. All is in tact. Interestingly, the fuse on the strut mount has a crack across the strip, which is almost causing failure. I'll replace that. What is that one for?

My AC works very well. I have no belt slippage, nor other issues. I'm thinking without the AUX cooling fan, it didn't have enough air flow to keep the pressures down, so it killed the compressor clutch.
I'm believing my fans failing or control relays is the root of the issue. Will fix that first, before looking at other things.

I just unplugged the power to the fans. Later today, I'm going to bench test. What would surprise me if they both failed at once. I've seen them both operating recently. Thinking maybe the relay took a cr@p, but speculation at this stage.

THANK YOU MUCH!
Doug

 

[gsxr]

The strip fuse at the strut mount should be for the HVAC blower/fan.

FYI, on high speed, the twin cooling fans bypass the ceramic resistor. If the fans work on high but not on low, the resistor wiring is suspect. If they don't work on high OR low, the fuse is next most likely, followed by the relay itself (which is unlikely).

 

[mwaldron]

The strip fuse at the strut mount should be for the HVAC blower/fan.

FYI, on high speed, the twin cooling fans bypass the ceramic resistor. If the fans work on high but not on low, the resistor wiring is suspect...

I keep reading that, but the high speed leg was jumpered (daisy chained) from one leg of the resister and that was the leg that failed and I lost all speeds. I never pulled the headlight to inspect as the visible end of the resister looked okay from that angle. It was some time until out of frustration that I pulled the headlight and saw that I was misinterpreting the bypassing the resister statement.

 

[DW SD]

I will check for 12V at the fuse, once I disconnect, for example, the coolant sensor. My wiring looks very intact and solid. zero corrosion on the this vehicle.

Doug

 

[DW SD]

I bench tested the fans with a 9V battery. They immediately spin. In doing this, I disconnected the harness connectors between the fans and upstream relays, etc. The plastic connecting housing on the fan side of the harness (with the male pins) fell apart in my hands.

Here's the weird thing I get 12V (13.7V) at the female side of the connection on the + pin. When I push the male connections back in to the female, I get zero V on the + male pin (easy to measure given the broken housing is now removed). Even though everything looks clean, I pulled the connection apart, used sandpaper, a small ignition file to clean up the male side, but still get no voltage across the connector. I guess my issue is there, though I don't see how - the pins seat firmly and tightly and no corrosion is visible.

Perhaps I'll have to buy new connectors and pins from Tom.

Doug

 

[gsxr]

Doug, this sounds like a bad connection upstream... are the fuses, relays, and wiring at the resistor/harness all ok? Pretty sure your issue is NOT related to the pins.

 

[DW SD]

Dave,
id agree it seems odd. But can't explain why I get full voltage at the female side of the connector until I plug in the pins and then it drops to zero?

Didnt have time for more troubleshooting. Probably need a schematic and start checking voltages. It does seem simple though. Two relays one resistor for low speed and one full voltage for high ground triggers from ECU and AC pressure switch.
??
thank you

Doug

 

[gsxr]

This is a classic symptom of a bad connection somewhere. There's enough of a connection to make the meter read +12v, but when any load is applied, the poor connection cannot pass enough current, and the voltage drops to near zero. The system is pretty simple, don't really need schematics unless all the basic stuff doesn't fix it. See if you can hear the relays click on when you either pull the temp sensor (high speed) or short the refrigerant pressure switch (low speed). If so, then you know it's not a control issue.

Did you physically remove the strip fuse for inspection? Remove the screws, etc?

 

[Klink]

This is a classic symptom of a bad connection somewhere. There's enough of a connection to make the meter read +12v, but when any load is applied, the poor connection cannot pass enough current, and the voltage drops to near zero. The system is pretty simple, don't really need schematics unless all the basic stuff doesn't fix it. See if you can hear the relays click on when you either pull the temp sensor (high speed) or short the refrigerant pressure switch (low speed). If so, then you know it's not a control issue.

Did you physically remove the strip fuse for inspection? Remove the screws, etc?

 

[DW SD]

Dave,
Been away from email for a few days. thank you for the comments. Can I get the relays to work with just ignition on, or does the engine have to be running? I couldn't hear the relays click, but maybe that was fan noise, etc from the engine. I measure full voltage at the fuse on both sides when the fan pins are plugged in. To me, that says the voltage drop is elsewhere. Is the fuse upstream or downstream of the relays?

I think this is the biggest CLUE: neither high nor low speed work. Something that they share would seem a likely issue. I get no response when I pull the high speed temp sensor plug.

thanks for your cycles. Pretty sure it is something simple here. Just haven't had much troubleshooting time.

Doug

 

[gsxr]

Relays will work with just ignition on, no need to have the engine running.

The 30A strip fuse (F22/2) is upstream and would prevent both high+low speeds from working. Ditto if the combo relay was bad. Also check the fuse which feeds the control portion of the circuit, 16A fuse #7.

Schematic attached from FSM (ETM PDF page 57, printed page 121/5).

 

[Klink]

Note that loose / burnt / damaged etc. wiring at the output side of the resistor can give you the same symptoms, as this binding point is the positive connection for output to the fans in any mode. This point is frequently neglected as everyone focuses on the much more common damage at the input side of the resistor.

 

[DW SD]

Hi Thank you for the additional info and schematic - VERY USEFUL. I did pull the combination relay - I do get the control voltage at pin 15x and high current input (12V+) @ pin 30. On the high speed relay circuitry, I get no ground trigger (temperature input) from the ECU even when I pull the coolant sensor connector. On the low speed relay circuitry I did see (ground) the ECU call for low speed fan with the AC on and fan running.

I wonder why the ECU doesn't call for fan when I pull the coolant connector?

I'm going to troubleshoot the low speed resistor circuitry. I may have two problems going on.

Doug

 

[DW SD]

OOOPs - looks like it is not the ECU calling for high speed fan, but push button unit. Is that the HVAC control unit? Can it be rebuilt? How much are new?

Doug

 

[Klink]

OOOPs - looks like it is not the ECU calling for high speed fan, but push button unit. Is that the HVAC control unit? Can it be rebuilt? How much are new?

Doug

Don't simply unplug the ACC coolant temperature sensor. That will not generate a command for high-speed auxiliary fan. You must also jump the female terminals in the plug. That should give you a high-speed auxiliary fan signal to the relay box. Your ACC control unit is probably fine.

 

[clarkz71]

Must depend on the year/model

My high speed fan comes on when I unplug the sensor B10/8

Keep in mind, this is a resistance based sensor, not on/off

Adding resistance like JimF cool harness does makes the fans come on sooner

Unplugging it is the most resistance you can have, no continuity at all

Bridging it is 0 resistance.

 

[Klink]

OOOPs - looks like it is not the ECU calling for high speed fan, but push button unit. Is that the HVAC control unit? Can it be rebuilt? How much are new?

Doug

Don't simply unplug the ACC coolant temperature sensor. That will not generate a command for high-speed auxiliary fan. You must also jump the female terminals in the plug. That should give you a high-speed auxiliary fan signal to the relay box. Your ACC control unit is probably fine.

Must depend on the year/model

My high speed fan comes on when I unplug the sensor

Interesting! I wonder if it depends on the vendor of the ACC panel? The Kammerer and the Bosch units do have different behaviors when short or open circuits are present. On my '93 500E I have to jump the sockets to get high speed aux fan (I just went to the garage and did it). I didn't comment on this earlier because I was also remembering that removing the plug would activate it. I'm thinking that it could be either way depending on the version and / or vendor of ACC unit installed at the time.

Also, just for clarification for others reading this: Do note that this is a variable resistance via temperature sensor circuit. It does NOT function as a "switch" in normal operation. When we unplug or short this control circuit we are only invoking a failure mode in the ACC panel. The ACC panel "notes" this as an implausible situation and does fault code for it. Apparently, some versions of the ACC panel vary as to whether an open or a short circuit will cause it to command the high speed auxiliary fan on.

 

[Klink]

Must depend on the year/model

My high speed fan comes on when I unplug the sensor B10/8

Keep in mind, this is a resistance based sensor, not on/off

Adding resistance like JimF cool harness does makes the fans come on sooner

Unplugging it is the most resistance you can have, no continuity at all

Bridging it is 0 resistance.

LOL, look what I was posting at the same time...

 

[clarkz71]

I've heard your results as well

I'll have to see what manufacturer my ACC panel is.

 

[DW SD]

Guys,
I found the problem after re-reading this thread and finding a procedure to remove the headlight unit so I could take a close look at the high-current low speed resister. There was very bad corrosion in the wires at the resistor stud. Copper was completely corroded to green and connector fell off of the end. I do now find 12V+ from the high speed fan relay and also from the low speed fan relay at the leads which route back to the relay panel.

This explains why I was seeing 12V+ at the female side of the fan connector. Once there was a load applied, the corrosion prevented any current flow and voltage dropped to zero.

Having cut out the resistor I added to emulate the "cool harness" functionality, I'm not sure I'll add a new one back in. It doesn't really matter if the fans come on at 107C or 98C, as long as they come on!

Thank you for the prompting along to help find the issue.

Doug