HOW-TO: Replacing 500E/E500 climate control air sampler ("asipirator") motor

[gerryvz]

One issue that pops up from time to time on the Mercedes-Benz W124 cars (including our 036 & 034 varietals) is one of the following:

A) a shrill whining sound from the passenger side of the dashboard, near the A/C & heater duct

B) loss of temperature control inside the car -- meaning that the HVAC system is either full "heat" or full "cool" depending on where the wheel is set

Either of these symptoms points to a failing (A) or failed (B) ACC "blower sampler" fan motor. This is a small, black, cylindrical plastic electric fan that is located behind and beneath the right side dashboard vent. The purpose of this vent is to suck air from the small square grill next to the overhead sunroof switch, through a long rubber tube that goes down the passenger-side "A" pillar and inside of the dashboard. From this "sample" of interior cabin air, the ACC system is able to determine current cabin temperature and adjust itself to maintain the desired temperature indicated via the dashboard thumbwheel. It's the baseline by which the ACC system does its calculations.

There is one way to test the function of this sampler fan: you take about a 1-inch square piece of light (tissue) paper and place it directly on the little grill next to the sunroof switch. Then you turn the ignition on (either accessory mode or turn the engine on) and the ACC system in any position (economy, defrost, AC, etc.) except the OFF mode via the pushbuttons on the dashboard. A working sampler fan will hold the piece of tissue paper up against the grill via a tiny "suction" action. If the paper falls off the grill downward onto the center console or seat, you know immediately that your sampler fan is inoperative.

Fans that are going out quite often - but not always - give a shrill whining noise. Sometimes they just up and quit as well.

I recently had this issue happen to me, by which when the thumbwheel was turned to full AC, the car got quite cold inside. And any other position other than full AC (even stlll in the rather blue "cool" range of the wheel) it went to heating mode. Furthermore, the tissue paper trick indicated that that sampler fan was not working. This was not a bad thing in my book because I had a bit of unfinished business from the removal of the dashboard and center console I performed last year to replace all six of the ACC "vacuum pods" (see HERE for that job). I hadn't replaced the 5 or 6 rubber vacuum "elbows" that connected the vacuum lines to the vacuum distributor (located behind the airbag in the dash next to the center console) which I had wanted to do, but had neglected to order new elbows; and I also wanted to better connect the flexible plastic duct-work running from the ACC heater box to the passenger side air duct -- I hadn't gotten a 100% positive fit.

My reasoning for replacing the vacuum elbow connectors is because they were original, 16+ years old and over time the holes get enlarged where the vac lines enter them. For the tightest possible seal, I wanted to use new elbows. You can see from the photo below the difference in diameter size between an "old" and "new" rubber vacuum elbow.

To do all of this work, the airbag & flexible duct had to come out so that I could access the vacuum distributor, as well as the sampler fan motor for replacement. The sampler fan is encased in a block of foam, and this assembly is then held in place with a C-shaped metal clip (see photos) so that it doesn't move around in the dashboard.

Tools needed to perform this job include:

• hand-held flashlight or Maglite
• 1/4" ratchet and extension, plus 8mm and 10mm sockets
• medium-sized Phillips screwdriver
• multimeter (to test power at the fan connector)

The part number for the fan is 000 830 19 08. As of February 2012, the MB list price for this fan is $63, and it is available through parts.com for $45. It is recommended to get the factory part, made by Bosch in Germany.

To replace all of these items, I did the following steps:

1) disconnected the battery via the negative terminal
2) removed the passenger side carpet and metal protective plate in the footwell, and unplugged the red airbag connector
3) removed the airbag via the long screw under the dash, and disconnected the two plugs that electrically attach to the back of it
4) removed the metal reinforcing pieces/airbag mounts
5) removed the black plastic flexible ducting piece running to the passenger side ACC vent
6) replaced 5 vacuum elbow connectors on the vacuum distributor
7) removed the sampler fan/foam assembly from its clip
8) briefly tested the sampler fan by reconnecting the battery, turning the ignition on, and seeing whether it was working or not (it wasn't turning)
9) checked the electrical connection to the sampler fan (after unplugging the fan) for voltage -- it tested out at 12.5 volts which was good
10) briefly attached the replacement fan to the connector to test its operation (it worked fine!)
11) installed the new sampler fan in the foam piece and re-clipped it into place
12) replaced the flexible plastic duct-work to the ACC box and the side vent, ensuring that everything was properly in place
13) checked speaker, night illumination and sampler fan wires in the dash for proper routing
14) re-installed metal airbag mount/dash reinforcement pieces
15) re-connected and re-installed passenger airbag
16) re-connected red plug in passenger side footwell and replaced metal plate
17) re-connected battery and reset (aftermarket) car alarm
18) entered radio code into radio
19) re-tested ACC sampler fan with a piece of tissue paper on grill (it worked!)

This is about a one-hour to 90-minute job if done slowly and carefully. Here are some photos attached to help illustrate the process.

Cheers,
Gerry

 

[gerryvz]

I've attached a couple of more related items, from MB documentation, for reference to this job.

Cheers,
Gerry

 

[gsxr]

FYI. While the passenger airbag is removed, this is a GREAT time to also check the seven vacuum lines for the climate control actuator pods under the dash, which control airflow to the vents. Use a Mity-Vac handheld vacuum pump, all seven lines should pump down to 25" vac and hold that steadily without dropping. Any line that does not hold steady vacuum indicates a failed vac pod. With the metal airbag mounting frame removed, you have easy access to the 7 vac lines, visible on the left side of the photos above. Both my 500E's had failed vac pods, I replaced all of them in my '92, and need to pull the dash and replace them in the '94 as well... oh joy...

BTW - great write-up, Gerry! Nice work, excellent photos.

 

[zman]

I have to say, essentially going in blind and knowing nothing of the "issues" that 500's have when I bought my 500, I want to take the opoortunity again to thank You Gerrry and Dave for providing such comprehensive and detail oriented information. This by far is the cream of the crop in terms of vehicle specific websites ...just like the cars themselves.

Zoran

 

[Christian_K]

Ok is the same system also used for manual climate-control "Klimatronic", you guys haven't had available in the 500E?

 

[gerryvz]

I don't know, Christian, because every W124 (and W126) I've seen in the US has had the automatic climate-control (ACC) system !!! Most Americans wouldn't have experience with anything BUT the ACC system !!

 

[Jelmer]

I have a feeling that in the non ACC cars it's different. On my car there's no air pulled in at all, same with 036. No matter how light the paper is, it won't stick. Oddly enough, the cabin temperature is still properly maintained (except that it doesn't annoy you with the fan speed, that's nice and manual).

 

[bing]

Well, I have to say that mine passes the GVZ tissue test-stuck firmly on the little grill by the sunrroof as described above, and I have the typical euro 'klimatronic' 2x temp thumbwheels. Like I mentioned before, I generally keep my temp set 20-22c (more or less in the middle) all year round and it regulates/maintains the cabin
Temp well. As GVZ described this the function of the aspirator.

ACC or Tempmatic this makes sense . Main difference is : ACC has automatic fan speed and air distribution, whereas the Tempmatic version you have to adjust these functions manually. However, the temp control/mode essentially works the same way in both types, 'ACC/Tempmatics' ,(albeit the latter has 2 wheels) in which the desired temp is set and maitained. Hence the name given tempmatic/klimatronic and the required aspirator for it to determine cabin temp.

@JB , sounds like on yours and 036 it's not working - unless of course earlier models were not fitted with this, but I doubt this very much. Are u sure that the temp flactuates according to cabin temp without adjusting the thumbwheel? Set it on 22c and leave it for the day. This time of the year in the mornings there should be warm air coming out but if you drive it in the afternoon or leave it parked under the sun, then cold air should come out! If you're having to adjust the thumbwheel quite often because you're feeling hot or cold then it's not right. Check if the hose is attached on that small grill by removing the interior/map light panel.

 

[gerryvz]

Indeed, if a constant "back and forth" adjustment of the climate control (i.e. it is fluctuating from hot to cold) is happening, then something is wrong with the system's self-regulation. It should be set at a desired temperature and the system should work to maintain that temperature through the cycling of the compressor, fans and vacuum controlled air pods in the dashboard.

Generally the air should be coming out of the dashboard in a "blended" sense (if set to a moderate/middle temperature). Only cold air should come out of the dashboard center vents; and mixed air should come out of the windshield defrost, under-dash and side-dash vents. The aspirator ("sampler") motor is an integral part of this system, but it is not the only portion of the system that regulates the temperature.

The good thing is that ample instructions exist from the factory for testing and diagnosing issues with the ACC (and very likely the manual climate control) system. If the light tissue paper is NOT sticking to the small over-head grill, then the aspirator motor is NOT getting an accurate read of the air in the cabin of the car, and thus is making assumptions of cabin air temperature based on other inputs, which ware undoubtedly going to provide completely inaccurate and false readings.

This is not an expensive nor difficult part to replace, but it is REQUIRED for proper operation of the climate control system. I wasn't explicitly aware (as bing indicates) that the non-ACC system contains this aspirator motor, but it does make sense that it would. Unfortunately about 99.9% of all 124s entering the US had the ACC system, so that is really all that we have experience/familiarity with as US owners.

Cheers,
Gerry

 

[Jelmer]

Bing: I'm positive the system is working as expected. On a cold morning you get warm air first, which slowly cools down until it's more-or-less the same temp as the cabin air. If it's really cold outside it'll stay way.

The wheels are always set at ~19C, although after my dualvalve has been fixed I have had it permanently at 21C. I honestly never touch it, be it in summer at 30C or in the winter at -5C.

One thing I should note, though: sometimes with a big difference between outside and cabin temperature, you can feel it adapting to the new temperature if I take a fast corner (in which the air is jumbled around inside). But I doubt that is because of the not so sucky pumpy.

[sub]Knowing my luck, it's probably simply clogged up at the moment, but will die in a few days [/sub]

 

[bing]

No matter how light the paper is, it won't stick

Oh man..you're testing it with the wrong kind of paper I reckon... Use 'Kleenex' brand not that 'ALDI' crap.!

I actually used Starbucks paper napkin (peeled the first layer or two i think so it's lite enough) to test mine and it stuck. Now go find a starbucks!:grin:

 

[azmurciev12]

hmmm! thanks for the post. i might need this. my car is just blowing cold air all the time -as in super cold. this might resolve it... i hope. i'll get to work on this.

 

[gerryvz]

Use the tissue paper trick to determine whether the motor is working or not.

 

[bing]

hmmm! thanks for the post. i might need this. my car is just blowing cold air all the time -as in super cold. this might resolve it... i hope. i'll get to work on this.

In Manila with that humidity?? First time I hear a Pinoy say it's "super cold!" Usually on Euro spec cars the A/C is never efficient enough.

Problem is, like most of us here complain about, the lowest speed fan setting (ACC or Tempmatic) is not low enough thus the blow of air can still be too much. It could do with one more notch IMO. Like Gerry says, do the tissue test and if it sticks I wouldn't worry too much.

 

[azmurciev12]

bing, i know it sound weird considering it's veryhot here in manila but the A/C in my E500 is really super strong. if it happens to be raining outside, it gets freezing inside.

anyway, i just tried the tissue test, and sure enough, the tissue dropped so i need to do more work. thanks for the tip. i always knew there was something wrong but just couldn't pinpoint what it was.

 

[mistermiata]

Gerry....

My E500 failed the tissue test so I am planning on doing the repair you outlined above. I want to replace the rubber vacuum elbows as well but did not see any part #'s for them in the write up.

Do you have the part #'s for them?

Thanks!

Andy

 

[gerryvz]

The part number is 201 805 01 03. You should order about 8-9 of them, just to have an extra or two on hand. If you were to pull the dashboard and replace all of the pods (something that everyone will have to do eventually), there are 14 of them specified in the EPC (7 for the Christmas Tree and 7 for the vac line attachments to the pods).

They should run around $2.00 apiece through parts.com (list price $2.70). You may be able to get them on the aftermarket for cheaper, but the rubber may not be up to the quality of the MB rubber.

I've found that particularly for soft parts like seals, hoses and connectors made of rubber or soft plastic, that the MB parts are far superior to aftermarket in terms of quality, longevity, durability and proper fit. Dave's recent post about the upper radiator hoses is another good illustration of this statement.

Cheers,
Gerry

 

[mistermiata]

Thanks Gerry!!

 

[gerryvz]

Did you get the job done, Andy?

 

[mistermiata]

Not yet Gerry, thanks for checking back though! Its on my to-do list, I will post here when its done. I have a new rear suspension squeak that needs to be addressed first.....very annoying!

I bought a 2000 Land Rover Discovery recently that has required most of my time getting its maintanance up to date, so the E500 has been a garage queen as of late. Gonna use the Disco for those wintry Northeast days and on Brigantine Beach (NJ) in the summers.

I will be getting rid of my E500 winter wheels and tires (17 inch AMG's with near new Pirelli snows) in the near future if anyone is interested.....I will post em up here 1st of course

 

[azmurciev12]

fantastic!! finally my car is blowing climate controlled a/c. even my MB workshop was surprised at the part. they never encountered replacing such item. thanks to gerry.

 

[gerryvz]

Excellent news !!

 

[Trae]

Just tested all three of my 124s and they all failed the test, however, I have had no issues with heating or cooling in AUTO on the control wheel. Could it be that I have never experienced a real MB automatic climate control the way it should be from the factory?
I'll try lighter tissue paper tomorrow.
If I find that they still fail the test, is this job worth doing even though I stay cool in the summer and warm in the winter? In other words, "just right."

 

[mistermiata]

That's my scenario too Trae....didn't know I had a problem until I failed the tissue paper test....cool in summer , warm in winter currently. I think the difference after the repair will be in the fine adjustments with the temp wheel. I notice now that small temp adjustment don't seem to make much difference.

I bought the part and am just waiting until I have some free time to install.

 

[Trae]

If I can just do one of my cars, the other two should be a lot quicker on the install.
What is the difference after the install? Smaller adjustments on the control wheel?

 

[gerryvz]

What is the difference after the install? Smaller adjustments on the control wheel?

The system will have the means to much more accurately determine internal cabin temperature, and automatically adjust the mix of cooling/heating air to match the temperature set at the thumbwheel. The tissue paper test should only take 30 seconds. Using a small square corner of a piece of toilet paper, or saran wrap, or cigarette paper, will work just fine. Everyone should have toilet paper.....

Cheers,
Gerry

 

[mistermiata]

Well Gerry.....I just did the sampler motor, turns out my old one as working fine! Redid the tissue paper test with the old and then the new sampler motor, and still wont hold the damn tissue! Cleaned off the grill and suction tube in the overhead panel and made sure everything was connected properl and still won't hold the tissue.....

So I put the new motor in, cleaned everything up, and replaced the rubber vacuum elbows.

I have a good used sampler motor if anyone wants it....

Weird....

 

[Trae]

The more I read, the more jobs I find to do on my 124s. I have not had time to do this yet, but it is on the list.
Andy, let us know what kind of differences you notice after you installed your motor.

 

[JordiC]

Andy, did you test the entire length of plumbing from motor to grill for leaks? If the motor is spinning then it must be drawing air in from somewhere. Maybe the medium you are testing with is too heavy or porous to allow it to stick. Gerry's last picture shows his paper sticking like glue. It does sound strange but if the a/c works properly then why worry.

 

[mistermiata]

Jordi,

That was my thoughts exactly. But, short of removing the whole length of plumbing (which looks daunting), I wouldn't know how to test the entire length of plumbing.

Used a regular old Kleenex, also tried a small piece of wax paper that the new motor was wrapped in with no luck.

The a/c does seem to work ok, just doesn't seem to respond to small temp wheel adjustments.

 

[JordiC]

Indeed, you would have to remove the a-pillar and probably the headliner to check, not fun. A hand held vacuum tester could be used to check for leaks.

 

[gsxr]

Don't forget the tube could be disconnected at the motor end. The tube is a single piece, IIRC, and normally would not need to be checked. No need to remove the headliner but you would have to pull the sin sun visor trim panel and A-pillar trims. If the tube is connected properly at the sensor, I'd look closely at the motor next (pull the passenger airbag for access).

Also: For the tissue test, don't use extra-thick or lotion-impregnated tissues. Plain single-ply facial or toilet tissue is what you want, and a SMALL piece, no larger than the grille opening at the sensor. The airflow is very, very slight and it cannot hold a heavy square of tissue in place.

 

[mistermiata]

OK, well I feel like an idiot!

Did as Dave suggested and tried a different paper for the tissue paper test (Cottenelle Toilet tissue to be specific) and it held up to the overhead grill, so i spent $50 bucks and several hours of my time for nothing!

So Trae, before you replace your sampler motor, only use the 500eboard approved tissue paper for your test to make sure you dont replace a perfectly normal functioning motor!

 

[Trae]

Thanks Andy!
I'll test again with "proper" paper!

 

[gsxr]

Gerry, does Kentster™ sell approved tissue in his store?

 

[gerryvz]

Wow, list price for this aspirator motor has gone up to $80, available through the typical discounters for ~$60. AutohauZ is selling gen-yoo-whine MB motors for north of $76.

That's about a 25% increase in the past couple of years. Ouch !

This is a really good part to get used at wrecking yards, to have 2-3 spares on hand. They don't wear out all that often. I also recall they were "NLA" for a time from MB, but it appears they are back in stock again.

Cheers,
Gerry

 

[LuisR]

Gerry good morning, would you have the documentation for a w126 1991 560SEL.

Thanks in advance!

Luis

 

[gerryvz]

As far as I know, the late W126/C126 setup is nearly identical to that of the W124 as illustrated. There is a small, black plastic aspirator ("air sampler") motor behind the passenger side dashboard/airbag, which is connected to a tube that goes up the passenger side A-pillar to the actual temperature sensor in the overhead area. Earlier W126 models had a small grill in the roof of the car; later W126 models have the temp sensor grill integrated with the overhead map light/sunroof switch console, just like on W124 models. The earliest W126 models (from the early 1980s) used, like the W116, a small temperature sensor grill mounted on the top of the dashboard in the center.

The late W126 models use the same aspirator motor part number as the W124 models do, and some W201 models, as shown above. The current list price from MB is $102.00, although it can be sourced in the $75-80 range.

Replacement of the aspirator/sampler motor should be identical to the procedure outlined above, although the W126 airbag mounting/install is slightly different than that of the W124, but close enough that anyone using the above procedure should be able to figure it out with complete ease.

Cheers,
Gerry

 

[NotaBene]

Gerryvz, thanks for this great post. Detailed and accurate. This issue has plagued my E420 for as long as I've owned it, as I've worked through the various issues (just finished replacing the Throttle Body which has transformed the driveability). Didn't want to even think about the thought of removing the dashboard. Looks like I won't have to!

I'll do the tissue test tomorrow!

Rob

 

[RicardoD]

Gerry,

Once again I must say you are the man! I fixed my aspirator today, very straight forward, but ran into a broken nut clip that will deny putting my car bake together until the replacement arrives. Some additional photos for people to help out. My original apsirator was a VDO part and the Bosch factory replacement (I bought a used one, new ones are $75 now at mboemparts.com ) are a little bit different but carry the correct Mercedes part number and work fine. Looking forward to proper climate control function now.

My tissue paper is floating now!!!

 

[JC220]

RicardoD- those clips are 'U clips' you should be able to get a matching one at any Autoparts store faster than waiting on the one from MB. Also- I bought a U Clip & screw selection pack off fleabay - a very useful kit to have in times of need like this.

 

[RicardoD]

Wow, now I know how the climate control is an E500 is supposed to work. Aspirator change has made all the difference. CCU is now a set it and forget it device. Before it was constantly making manual adjustments. Can't believe I put this fix off for as long as I did.

 

[French02chris]

One issue that pops up from time to time on the Mercedes-Benz W124 cars (including our 036 & 034 varietals) is one of the following:

A) a shrill whining sound from the passenger side of the dashboard, near the A/C & heater duct

B) loss of temperature control inside the car -- meaning that the HVAC system is either full "heat" or full "cool" depending on where the wheel is set

Either of these symptoms points to a failing (A) or failed (B) ACC "blower sampler" fan motor. This is a small, black, cylindrical plastic electric fan that is located behind and beneath the right side dashboard vent. The purpose of this vent is to suck air from the small square grill next to the overhead sunroof switch, through a long rubber tube that goes down the passenger-side "A" pillar and inside of the dashboard. From this "sample" of interior cabin air, the ACC system is able to determine current cabin temperature and adjust itself to maintain the desired temperature indicated via the dashboard thumbwheel. It's the baseline by which the ACC system does its calculations.

There is one way to test the function of this sampler fan: you take about a 1-inch square piece of light (tissue) paper and place it directly on the little grill next to the sunroof switch. Then you turn the ignition on (either accessory mode or turn the engine on) and the ACC system in any position (economy, defrost, AC, etc.) except the OFF mode via the pushbuttons on the dashboard. A working sampler fan will hold the piece of tissue paper up against the grill via a tiny "suction" action. If the paper falls off the grill downward onto the center console or seat, you know immediately that your sampler fan is inoperative.

Fans that are going out quite often - but not always - give a shrill whining noise. Sometimes they just up and quit as well.

I recently had this issue happen to me, by which when the thumbwheel was turned to full AC, the car got quite cold inside. And any other position other than full AC (even stlll in the rather blue "cool" range of the wheel) it went to heating mode. Furthermore, the tissue paper trick indicated that that sampler fan was not working. This was not a bad thing in my book because I had a bit of unfinished business from the removal of the dashboard and center console I performed last year to replace all six of the ACC "vacuum pods" (see HERE for that job). I hadn't replaced the 5 or 6 rubber vacuum "elbows" that connected the vacuum lines to the vacuum distributor (located behind the airbag in the dash next to the center console) which I had wanted to do, but had neglected to order new elbows; and I also wanted to better connect the flexible plastic duct-work running from the ACC heater box to the passenger side air duct -- I hadn't gotten a 100% positive fit.

My reasoning for replacing the vacuum elbow connectors is because they were original, 16+ years old and over time the holes get enlarged where the vac lines enter them. For the tightest possible seal, I wanted to use new elbows. You can see from the photo below the difference in diameter size between an "old" and "new" rubber vacuum elbow.

To do all of this work, the airbag & flexible duct had to come out so that I could access the vacuum distributor, as well as the sampler fan motor for replacement. The sampler fan is encased in a block of foam, and this assembly is then held in place with a C-shaped metal clip (see photos) so that it doesn't move around in the dashboard.

Tools needed to perform this job include:

• hand-held flashlight or Maglite
• 1/4" ratchet and extension, plus 8mm and 10mm sockets
• medium-sized Phillips screwdriver
• multimeter (to test power at the fan connector)

The part number for the fan is 000 830 19 08. As of February 2012, the MB list price for this fan is $63, and it is available through parts.com for $45. It is recommended to get the factory part, made by Bosch in Germany.

To replace all of these items, I did the following steps:

1) disconnected the battery via the negative terminal
2) removed the passenger side carpet and metal protective plate in the footwell, and unplugged the red airbag connector
3) removed the airbag via the long screw under the dash, and disconnected the two plugs that electrically attach to the back of it
4) removed the metal reinforcing pieces/airbag mounts
5) removed the black plastic flexible ducting piece running to the passenger side ACC vent
6) replaced 5 vacuum elbow connectors on the vacuum distributor
7) removed the sampler fan/foam assembly from its clip
8) briefly tested the sampler fan by reconnecting the battery, turning the ignition on, and seeing whether it was working or not (it wasn't turning)
9) checked the electrical connection to the sampler fan (after unplugging the fan) for voltage -- it tested out at 12.5 volts which was good
10) briefly attached the replacement fan to the connector to test its operation (it worked fine!)
11) installed the new sampler fan in the foam piece and re-clipped it into place
12) replaced the flexible plastic duct-work to the ACC box and the side vent, ensuring that everything was properly in place
13) checked speaker, night illumination and sampler fan wires in the dash for proper routing
14) re-installed metal airbag mount/dash reinforcement pieces
15) re-connected and re-installed passenger airbag
16) re-connected red plug in passenger side footwell and replaced metal plate
17) re-connected battery and reset (aftermarket) car alarm
18) entered radio code into radio
19) re-tested ACC sampler fan with a piece of tissue paper on grill (it worked!)

This is about a one-hour to 90-minute job if done slowly and carefully. Here are some photos attached to help illustrate the process.

Cheers,
Gerry

I know it's a super old post, but a friend of mine has clicking sound from the unit.. And one of the pod is definitely gone!!
However, when he comes at slow speed, the car try to cut off (erratic idle) and clicking intensifies (the erratic idle comes when clicking happens) ... Would a vacuum leak in those pods and failing fan cause a vacuum leak big enough to create the erratic idle at low speed??
(everything is fine in the car.... So we know it's definitely a vacuum leak or maybe a dirty ICV (which has not been cleaned yet))

 

[gsxr]

I know it's a super old post, but a friend of mine has clicking sound from the unit.. And one of the pod is definitely gone!!
However, when he comes at slow speed, the car try to cut off (erratic idle) and clicking intensifies (the erratic idle comes when clicking happens) ... Would a vacuum leak in those pods and failing fan cause a vacuum leak big enough to create the erratic idle at low speed??
(everything is fine in the car.... So we know it's definitely a vacuum leak or maybe a dirty ICV (which has not been cleaned yet))

What year/model car does your friend have? What unit is clicking?

 

[French02chris]

What year/model car does your friend have? What unit is clicking?

climate control air sampler (fan) motor.​

Car is 1992 300E.
The erratic idle at low speed only happens when the clicking of the fan (behind the glovebox) starts... Like a vacuum leak.
Is it just a weird coincidence?

 

[French02chris]

What year/model car does your friend have? What unit is clicking?

Also the only code (using the little obd1 reader) is for Engine coolant temp sensor out of range.

 

[gsxr]

Car is 1992 300E.
The erratic idle at low speed only happens when the clicking of the fan (behind the glovebox) starts... Like a vacuum leak.
Is it just a weird coincidence?

1992 300E has different systems than the 400E/500E. The clicking is likely a symptom of a different problem, not the cause of the erratic idle. When this occurs, check voltage at the battery... if not 13-14v, the OVP relay might be the culprit.

And no, a vacuum leak from any HVAC pod cannot cause an erratic idle. The HVAC clicking may be due to auxiliary coolant pump failing, if the current draw is too high. Try unplugging the aux coolant pump and see if there is any change. This also should not cause the erratic idle though.

Test the engine coolant temp sensor and see if the measured resistance matches estimated actual temp, replace the sensor (OE only) if it's bad.

 

[French02chris]

What year/model car does your friend have? What unit is clicking?

Also the only code (using the little obd1 reader) is for Engine coolant temp sensor out of range. If I'm

1992 300E has different systems than the 400E/500E. The clicking is likely a symptom of a different problem, not the cause of the erratic idle. When this occurs, check voltage at the battery... if not 13-14v, the OVP relay might be the culprit.

And no, a vacuum leak from any HVAC pod cannot cause an erratic idle. The HVAC clicking may be due to auxiliary coolant pump failing, if the current draw is too high. Try unplugging the aux coolant pump and see if there is any change. This also should not cause the erratic idle though.

Test the engine coolant temp sensor and see if the measured resistance matches estimated actual temp, replace the sensor (OE only) if it's bad.

Thank.. I will tell him to replace the coolant temp sensor..
However the clicking is 100% coming from the hvac fan.. Just apparently it's just a weird coincidence.
Ovp and MAS unit have been replaced.
Voltage is perfect.

 

[gsxr]

Thank.. I will tell him to replace the coolant temp sensor..

There is a separate coolant temp sensor for the engine, vs the HVAC system. Make sure to replace the correct one. Also, if the code has not been cleared, it could be a false positive... but if the code has been cleared AND it comes back, the sensor might actually be defective. The sensors are pretty rare failures though, and I don't think it will fix the problem.

However the clicking is 100% coming from the hvac fan.. Just apparently it's just a weird coincidence.

100% from the blower motor fan under the windshield? This is very different than clicking behind the glovebox (from the 7-port vacuum manifold). Or, clicking from the aspirator motor. If not sure if the clicking is from the aspirator or vac manifold, he will need to pull the glovebox and verify the exact source.

Ovp and MAS unit have been replaced.
Voltage is perfect.

OK. Next easy test is to measure the resistance of the auxiliary coolant pump. If it's near zero ohms (like, 0.0-0.1 or so) that could be the root cause of the clicking behind the glovebox. Disconnect the pump and see if the clicking remains. I think normal resistance is something like 1.0 ohms? Can't remember exactly.

 

[French02chris]

100% from the blower motor fan under the windshield? This is very different than clicking behind the glovebox (from the 7-port vacuum manifold). Or, clicking from the aspirator motor. If not sure if the clicking is from the aspirator or vac manifold, he will need to pull the glovebox and verify the exact source.

Yes clicking is from aspirator fan behind glovebx