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bing
05-29-2011, 03:20 PM
After high speed driving today with the A/C on I noticed all of sudden that it wasn't blowing cold and the aux fans were continuously on even with the engine temp below 80c. When I got to my destination I popped the hood and check if the compressor was spinning but it wasn't! Also at this time fans were still at max.. :wtf:
I allowed the engine to cool down for about an hour while having lunch but as soon as I turned the ignition on again and just before crank I could hear the fans roaring already (this is with HVAC completely shut down). Crank it, fired up and fans on.

I had similar problem last winter when the fans were coming on when cold, to which it was isolated from the "refrigerant switch on receiver dryer". So had new switch fitted, A/C evac and recharged. This was about 2months ago and all was working fine, tried and tested through heavy traffic - A/C blowing cold and fans activating when they should (in my case, around 95-97c coz of 'cool harness mod').

Based on this, as I did in the past which stopped the fans with considerable time of testing, I disconnected the refrigerant switch to see if the fans would switch off but nothing - fans still stayed on! :banger:

Anyway, being 80miles away from home I drove back, averaging 85-95mph, with fans roaring away and decided to leave HVAC on cold to see to if cold air will eventually come. And it did after about 20mins be it somewhat intermittently, I think, but cold enough for my partner to complain.. When I reached town at a slower speed and in moderate traffic (temp at 80c) I could hear the fans cutting in on/off but eventually off and decided to switch off HVAC. Stopped for Ice cream in town for about 20mins, restarted and no fans roaring till I reached home.

Any thoughts or same experience guys? And is this all connected , A/C compressor not working properly and Aux fans staying on?? Right now I'm thinking that it wasn't the refrigerant switch that cause the fans to activate early in the past. Saying that though, when I disconnected the old switch it did stop the problem and I drove it for weeks without it, albeit winter .

Cheers,
Bing

gsxr
05-29-2011, 05:15 PM
The elec fans trigger on low speed based on refrigerant pressure (red switch at the receiver/dryer, behind/below driver's headlight). They trigger on high speed based on coolant temp from a sensor on the front of the intake manifold below the plastic cover in front of the airbox, the 2-prong sensor. This sensor sends a signal to the pushbutton unit inside the car which is what actually triggers the fans on high speed. Most likely either the sensor is bad, or the pushbutton unit. If you have "cool harness" installed, remove it.

BTW, engine temp should not be under 80C when warmed up - wasn't clear from your post if that was during warmup phase or not. If it is below 80, either the t-stat is bad, or the sensor/gauge isn't reading accurately.

:detective:

gerryvz
05-29-2011, 05:51 PM
Sounds to me like you don't have enough refrigerant in the system to trigger the compressor. When the system is on the hairy edge of having enough pressure, then sometimes the compressor will operate and sometimes not. I'd have the system leak-tested (with fluorescent dye) and see if/where there are any leaks that are letting refrigerant out of the system.

Unlike earlier cars (like my 560SEC and early W124s such as the 300E) which have a distinct "Klima" relay that in and of itself controls the compressor's operation, and which wears out due to age and temperature/use, the E500E has its compressor control integrated into the Base Module (BM) which is the computer box in the CAN box that has the four 10 Amp red fuses on the little clear plastic-lidded compartment on the top of the box. It is possible to troubleshoot this compressor control function with an ordinary multimeter, however.

There are two relays that control operation of the auxiliary fans, located in the relay box directly behind the fusebox. These two relays are identical and are on the left edge of the relay box toward the rear (see attached diagram). You may want to check that these relays are operating properly by removing and examining them physically. Very early 500Es (those built from July 1991 through May of 1992) only had one resistor in the relay box, but this shouldn't be applicable to the very vast majority of cars imported into the US.

If you have the ability to use a blink counter (the homemade tool works well for this) in the 38-pin CAN plug, you can read out stored fault codes pertaining to this system. I believe these are analog codes. Depending on the code that it is, it will help you pinpoint the condition present and/or component that is causing the condition.

Cheers,
Gerry

gerryvz
05-29-2011, 09:32 PM
This document might also help you isolate and diagnose things with regard to compressor operation:

http://www.w124-zone.com/downloads/MB%2 ... 83-605.pdf (http://www.w124-zone.com/downloads/MB%20CD/W124/w124CD1/Program/Climate/83-605.pdf)

Cheers,
Gerry

bing
05-30-2011, 02:10 PM
Thanks Dave/Gerry for your input. Drove the car today with lots of stops and start ups since I was doing a few errands and all seems fine. No early activation of fans and AC working as it should. Now garaged and covered for at least a week or till I need to make long trips. I will see if the problem arises again at some point and if it does I'll work on your suggestions. And in the meantime, I'll take it to my local indie to see if there are any stored fault codes on Star. I'm a bit of a lame duck when it comes to using a blink counter and reading codes :thumbsdown:

Sounds like aux fan and AC compressor are 2 separate issues then? The fan possibly switches/relay and AC low refrigerant or fuse in the CAN box? Basically, what I'm trying to say is that because of non activation of AC compressor this should not keep the Aux fan running, so not a connected problem?

Dave - where is the cool harness attached ( i know it has this mod as confirmed by PO) and is it easy to remove? Also do u have p/n and its location for the push button switch inside the car?

Oh the engine temp is normally around 90c. It was only lowering at 80c coz of the problem fan being on all the time. Today it was normal at 90 and fan activated just below 100c. Btw, at what temp should they activate without cool harness??

Thanks a lot!
Bing

gsxr
05-31-2011, 04:41 PM
Sounds like aux fan and AC compressor are 2 separate issues then?
I think so, based on what you describe.



The fan possibly switches/relay and AC low refrigerant or fuse in the CAN box?
The fan sensors are on the engine & receiver/dryer. The relays are in the rear half of the fuse box. Nothing is in the CAN box.



Basically, what I'm trying to say is that because of non activation of AC compressor this should not keep the Aux fan running, so not a connected problem?
Correct, the fans will run on high speed based on engine temp, regardless if the AC compressor is running or not.



Dave - where is the cool harness attached ( i know it has this mod as confirmed by PO) and is it easy to remove?
Cool harness is attached at the 2-pin sensor on the intake manifold, under the plastic cover in front of the airbox, near the other temp sensors. It will look like this (http://www.k6jrf.com/CTS_2.gif) and can be removed easily if desired.




Also do u have p/n and its location for the push button switch inside the car?
There is no "pushbutton switch" inside the car... it is the climate control unit in the console with the temp wheel / pushbuttons / etc. This unit also controls the elec fans, it looks at the temp signal from the sensor at the engine, and triggers the relay in the fuse box to turn the fans on & off as needed. The CoolHarness adjusts this to a different temp.



Btw, at what temp should they activate without cool harness??
I believe the fans trigger on high speed around 102-105C, assuming your sensors are good and the dash gauge is accurate. The CoolHarness will reduce this to 92-98C (approx) depending which one you have installed.

:bartman:

bing
06-02-2011, 04:18 PM
Dave,

Thanks for the step by step response. Where the aux fan is concerned I will replace the sensor on the intake manifold ( I guess this is the same sensor where the 'cool harness' is installed, therefore replacing it will eliminate this ?? ), check relays and replace if necessary. Any idea roughly the cost and P/N of this sensor, please?

With the A/C i will monitor and if it stops cooling again I will have a leak test and freon check. Strange that at the moment it's working well. :boxing: It was recently evac and recharged when I had the switch on the receiver dryer changed. If you remember I PM'd you about this?

Thanks a lot!
Bing

bing
06-04-2011, 05:48 PM
And so it turns out, after buying a new temp sensor, It's time for a new upper wiring harness :roll: !

Just as I fired her up, after a week sitting, the fans roared instantly. While ticking over with the fans running I disconnected the plug from the sensor (blue 2 prongs on intake manifold) to see if the fans stopped, but still they were running :? . Then by chance I pinched the end wire of the plug (while disconnected) they stopped. Played with it a bit more, twisting and pinching the same area of wire, and yep fans were clicking on/off. Pulled the insulation back and voila - copper and cracks right in front of my eyes :omg: . Just as expected and much like what's normally revealed when one sends pictures of their old ones (seemingly proud of what they had replaced ). It's something that I had been putting off in investigating, now the time has come. So I proceeded to check obvious areas, injectors and other sensors/plugs a like - all knackered, gonners, shit, caput!!

Anyway 2 new sensors later - refrigerant and temp replaced unnecessarily, an order of an E500E favorite part is placed and 600 smackers() later gone to MB stealers. Just wished I had seen Christian K's post about a guy in germany who makes better ones for 250euros :banger: I may order the lower one from him though. I've yet to check these - what are the common signs when the lower harness is bad ?? It's something that I'll have to check when I'm underneath again, which will be soon as I spotted another oil leak ( will post another thread about this)..

:banana1:

Bing

askd9280
11-09-2011, 08:08 PM
I have a new upper harness. When the connector to the two prong coolant temp sensor is unplugged the aux fans engage at the high setting. Is this normal.

Thanks.

gsxr
11-09-2011, 10:16 PM
Yes, that is normal, and it's a handy test to see if both electric fans are working on the high speed setting.

:banana2:

askd9280
11-09-2011, 11:46 PM
Yes, that is normal, and it's a handy test to see if both electric fans are working on the high speed setting.

:banana2:



One more question. When I plug the cool harness ch92 to the upper harness connector but do not plug it to the cts 2 2prong sensor the aux fans stop working. Is this correct?

Thanks.

gsxr
11-10-2011, 10:02 AM
Yes, that is also correct... the CoolHarness has a resistor inside, and the harness "sees" that resistor as a temp reading, and turns the fans off. Totally normal.

:rugby:

askd9280
11-10-2011, 08:29 PM
Great! Thanks for the advise. :)

vatc5637
08-29-2012, 04:16 PM
I had a similar problem on my '94 E420 with 171k miles. Thanks to this and other threads on this board, examined the high temp relay (15A) behind the fuse box and replaced a blown 15A fuse on the relay. When I tested the aux fans by pulling the two prong temp sensor, the aux fans kicked on immediately. Problem solved I thought. Couple of days later, noticed high engine temps with a/c on. Checked relay again, blown fuse. Tried a 20 amp fuse this time, tested it again and it everything seemed to work fine. Later used a/c again, with high temps resulting from no aux fans due to a blown 20A fuse. Clearly, I've got a short or other problem somewhere. Any suggestions as to what it might be and potential solutions? I don't understand why the aux fans work immediately after I replace the fuse (checked fuse after testing aux fans, still good), but fuse then blows later. Upper wiring harness is 8 mos old, resistor and attached wire are new and were replaced at same time as wiring harness. A/C otherwise works well as far as I can tell.

gsxr
08-29-2012, 04:23 PM
Keep in mind that the 15A fuse/relay routes power through the resistor, while the 30A fuse/relay does not. Pulling the wire at the 2-prong sensor triggers the 30A fuse/relay, which verified that high speed is working (also verifies the fans function). However if you have a short in the circuit with the resistor, you'll keep blowing the 15A fuse whenever the AC pressure switch closes. Have you physically inspected the wires at the resistor, behind the driver's headlight? You will need to check for voltage there while shorting the red pressure switch at the receiver/drier to trigger the 15A (low speed) relay.

I had to fix this on both my E420's this spring. Before & after photos below.

https://www.500eboard.com/forums/images/imported/2012/08/106.jpg

https://www.500eboard.com/forums/images/imported/2012/08/107.jpg

:watermelon:

vatc5637
08-29-2012, 05:25 PM
Oh . . . got the relays mixed up. Did not do more than a casual inspection of the resistor and wire because they were less than a year old. Will take the time to examine them more carefully. Thanks very much for the suggestion.

Jelmer
08-30-2012, 02:19 AM
I'd call that before and before photo's, though?

bing
08-30-2012, 02:39 AM
Lol...JB, I just knew you'd pick up on this?? Dave, can we have after and after photos , please?!!

vatc5637
08-30-2012, 09:12 AM
Pulled cover and . . . you were correct, my a/c resistor wire looked just like the one shown in your picture. Its seems like the best way to repair the wire and replace the resistor is to first remove the driver's side headlamp unit, can you confirm? Also do you have a part number for the resistor? A related post had a picture with a Beru # but I couldn't use it to locate the part in the .parts.com inventory. Thanks.

gsxr
08-30-2012, 10:51 AM
Wooops! My bad. No soup for me! Linky fixed now.

:jelmerian:

gsxr
08-30-2012, 10:54 AM
Pulled cover and . . . you were correct, my a/c resistor wire looked just like the one shown in your picture. Its seems like the best way to repair the wire and replace the resistor is to first remove the driver's side headlamp unit, can you confirm? Also do you have a part number for the resistor? A related post had a picture with a Beru # but I couldn't use it to locate the part in the .parts.com inventory. Thanks.
I was able to do it with the headlamp in place, but it will be a LOT easier with the headlamp removed. The resistor was fine on both my cars, it was just a broken wire. You may want to double-check before buying a new resistor (p/n 000-158-32-45, $72 USD OE list, about $25-$35 aftermarket). If your resistor is broken or shorted out, then yes it should be replaced.

https://www.500eboard.com/forums/images/imported/2012/08/108.jpg

:roadrunner:

vatc5637
08-30-2012, 12:51 PM
Yup. . . Ceramic portion of resistor cracked in two. New part ordered. Thanks for the advice and quick responses.

gerryvz
08-30-2012, 01:41 PM
Wooops! My bad. No soup for me! Linky fixed now.I think whenever Dave's bad (as with his trying to call BS on the AMG book) it should be only Mushroom soup for him ! :joke:

gsxr
08-30-2012, 01:45 PM
I think whenever Dave's bad (as with his trying to call BS on the AMG book) it should be only Mushroom soup for him !
Hey now. I wasn't trying to call BS on the AMG book, I was calling flat-out BS on the AMG book.

http://img4-2.myrecipes.timeinc.net/i/recipes/ck/06/01/mushroom-soup-ck-1142025-l.jpg

https://www.500eboard.com/forums/images/imported/2012/08/3.gif

Bondavi
01-10-2013, 08:15 PM
Is there only one wire connected at the resistor on one end? I wouldn't think so, but apparently my E320 has it like this. No corrosion on that one end, but I can't seem to find a 2nd wire nearby hanging.

samiam44
01-10-2013, 08:38 PM
Not a very good choice of shroom dave=)

gsxr
01-11-2013, 10:41 AM
Is there only one wire connected at the resistor on one end? I wouldn't think so, but apparently my E320 has it like this. No corrosion on that one end, but I can't seem to find a 2nd wire nearby hanging.
One wire attaches to each end. If one end of your resistor is missing a wire, that ain't right...

:mushroom: :mushroom: :mushroom:

vexed
01-11-2013, 12:43 PM
One wire attaches to each end. If one end of your resistor is missing a wire, that ain't right...

:mushroom: :mushroom: :mushroom:

Yes and if one of the posts looks like this you need an new resistor13948

JordiC
06-01-2013, 05:46 PM
I had this same issue last year and a new resistor cured it. I'm sorry for not viewing this post sooner, as I think I could have been of assistance.

This week, though, my problem is different. My electric fans are not turning on but my a/c operates properly. I have checked the strip fuse. The resistor, replaced last year, still looks good. When I remove the temp. sensor on the manifold I can hear the relay click but the fans won't turn. When I remove and bridge the switch at the a/c receiver I can also hear the relay click but, again, the fans won't spin. Visual inspection of relays and fuses in the box showed nothing wrong. I can't check the fans themselves as I didn't have a 12v power source with enough juice to spin them on hand.

This week I will apply power to the male end of the plug located under the a/c drier and if the fans don't spin I can assume they're both kaput. Is this the correct assumption?

:?:

DW SD
06-01-2013, 08:35 PM
Check for 12v to the fans father the relay clicks

DW SD
06-01-2013, 08:36 PM
I meant after the relay clicks

JordiC
06-01-2013, 10:25 PM
I meant after the relay clicks

Understood, will do. Does the temp sender plug need to be bridged or just unplugged? I heard relay clicking just by pulling the plug, whereas the drier switch had to be bridged.

DW SD
06-02-2013, 06:45 PM
I would not bridge, just measure for 12V at the plug after the relay clicks on. If 12V exists and the fans don't turn, i think you found the problem Or unplug them and apply 12V from the battery directly and bench test them.

Doug

emerydc8
06-03-2013, 04:43 PM
Can't you just unplug the coolant temp sensor on the intake to see if the fans go to high, or has that already been tried?

DW SD
06-03-2013, 05:06 PM
Can't you just unplug the coolant temp sensor on the intake to see if the fans go to high, or has that already been tried?
+1 better answer than mine!

bing
06-03-2013, 05:07 PM
Tried i think


When I remove the temp. sensor on the manifold I can hear the relay click but the fans won't turn.
:?:

emerydc8
06-04-2013, 07:06 PM
I don't know if it matters, but was the motor running when you tried it?

JordiC
06-04-2013, 07:16 PM
I don't know if it matters, but was the motor running when you tried it?

Engine was off and cold but ignition was on. I couldn't hear the relays otherwise. I'm still looking for time this week to finish checking things.

Trae
06-09-2013, 01:03 PM
Hi guys,
Today, I experienced this condition:
1. AC on high/max cool.
2. Coolant temp. 100C.
3. Neither fan spinning.
4. NO codes on ANY pin.

Shouldn't the fans spin in this condition?

8899
06-09-2013, 03:50 PM
Don't they turn at 107*C?

Jelmer
06-09-2013, 04:08 PM
As Dave said, earlier:

The elec fans trigger on low speed based on refrigerant pressure

With the AC on max, they should kick in a few times a minute.

emerydc8
06-10-2013, 01:07 AM
You might be right on the edge of the high speed fans triggering, but the low speed fans should probably cycle on and off. Have you tried using a paperclip to jump the leads going to the receiver dryer to see if the low speed fans come on? If they do, then you are probably low on freon.

JordiC
06-24-2013, 03:01 PM
Finally had some free time today to test with a multimeter and it confirmed what I thought. The fan plug shows 12 volts when the temperature sensor is removed and also when the pressure switch is bridged. The switches and relays are working properly and the fans are not. I applied 12 volts directly to the plug and the fans did not spin. I have already browsed gsxr's separate post on fan R&R, anticipating doing this job myself along with other cooling related maintenance. Great timing considering the weather is getting steamier.


:miserable:

JordiC
06-24-2013, 08:11 PM
Just to make one thing certain, the black connector in the photo, shown outside of its retaining clip, goes unfused directly to the fans correct?

18567

JordiC
07-09-2013, 09:11 PM
Can anyone confirm the above?

gsxr
07-09-2013, 10:47 PM
Can anyone confirm the above?
Yes... I am 99.44% certain that is correct. Make sure you are applying 12v to the correct side of the plug, btw, i.e. to the side which goes to the fans. And make sure the 12v source is not from the other half of the plug, for test purposes use a spare battery, or something along those lines.

I just had to do the repair shown in post #15 above on my new 500E, btw. The top wire connection at the ceramic resistor was completely corroded apart. Interestingly, the 500E has two wires at that top terminal, where the 400E/E420 only has a single wire. Apparently the 500E has slightly different wiring setup, possibly with heavier gauge wire, compared to its little brother.

:5150:

kre8tive202
11-15-2016, 11:20 PM
Does anyone know what this is and maybe a part number. I dont like the rusted look of the terminals and wanted to change it outmhttps://www.500eboard.com/forums/images/imported/2016/11/41.jpg

Sent from my SAMSUNG-SM-G890A using Tapatalk

vatc5637
11-16-2016, 12:20 AM
Auxiliary fan resistor, more info here A/C & Auxiliary Fans (http://www.500eboard.com/forums/showthread.php?t=1366)

kre8tive202
11-16-2016, 12:41 AM
Just bought it, thank you

Sent from my SAMSUNG-SM-G890A using Tapatalk

nocfn
11-16-2016, 07:32 AM
It is good to see the heat shield removed from that resistor. Once you rebuild the wires there and replace the resistor, do some surgery. The plastic in your picture is the air dam, notice you have a little round plug. Pop that plug out, you may want to fix a tube to allow air to blow across that resistor. In my case, I cut an additional hole about the diameter of a quarter to flood that resistor with air. At night that thing will glow, and the cool/heat process allow for rapid oxidation of those connections and wires. Looks like that has started.

gsxr
11-16-2016, 07:59 AM
Merged threads on same topic. Be prepared to replace fried wiring as shown in post #15 earlier in this thread...

:shocking: