W124 aux fan spins backward - PeachParts Mercedes-Benz Forum

p. rex · #1 07-13-2008, 01:38 AM

That's about it. One of the two auxiliary fans (recently replaced) on my '91 300E is turning the wrong way. It works fine otherwise and turns on when it should, it just is turning counter-clockwise from the front, and isn't doing its job.

Since the fan is new, I doubt there is any malfunction with it. Maybe it was wired wrong? At the least, if anyone could tell me how the fan is wired, I would enormously appreciate it.

Also, my passenger side low-beam headlight is dim; the high beam doesn't work. The driver side corner light doesn't light up. Oddly, sometimes recently it has been the left headlight displaying the same problem. Any ideas as to why this may be occurring?

Thanks for the help.

compress ignite · #2 07-13-2008, 02:28 AM

#1. Who replaced the Aux Fan?(They should correct the wiring problem)
[Although, Someone who wired my fan backwards and didn't check it
FIRST; would not have the opportunity to screw up a second time.]
Any chance this fan is driven by a belt from the other Aux fan?
#2. 'This car a "SUBMARINE"? [What we call Katrina (And Etc.) Victims]
['Though,really the Victim is the unknowing "New" owner.]
(people who sell flood cars are called Submarine Captains...
Very much shortened life spans, if caught)

280EZRider · #3 07-13-2008, 02:31 AM

Your recently-replaced aux fan was wired inavertanly in reverse. Just reverse the two wires. Polarity will be reversed and fan will spin in the correct direction.

It sounds like you have some bulbs about die.

p. rex · #4 07-13-2008, 04:22 AM

Ah, so it is exactly as I thought. Are these wires easily accessible or do I have to do some disassembly to get to them? While I have lost faith in the mechanic that performed the work, I will certainly make him fix this error before I take my business elsewhere (probably MPH automotive, as I'm in Houston).

The light problems are probably just the bulbs and nothing more sinister? I know that the '91 model year is not susceptible to the wiring harness issue present in later W124s, so I'll change the bulbs out and see what happens.

I can say with certainty the car has never been flooded. It was given to me by a relative who purchased it from the original owner (a friend of his) in 1998. Said relative daily-drove the car from that time to the present, when he bought himself a G37 coupe and gave the Benz to me.

I am a glutton for automotive punishment, so the car is perfect for me.

duxthe1 · #5 07-13-2008, 10:46 AM

The harness that needs to be corrected is buried! The radiator and condensor needs to be removed before the the aux fan shroud can taken off to gain access to the offending connector. You should DEFINATELY take it back to the shop who did the work and have them warranty the whole job as this requires opening the A/C system.

Occasionally the fans do come with the wires reversed in thier connector. I always check the operation and direction of rotation before I start reassembly. I bet your shop will too in the future.

deanyel · #6 07-13-2008, 01:04 PM

It seems to me (not sure) that it's an irreversible plug, and therefore not likely the shop's fault. MB does suggest removing all that stuff and coming at it from the back but it's easier to do it from the front, especially for someone without the AC evacuation equipment. You have to take the front bumper off but that's quite easy, 6 or 8 bolts as I recall. There's a DIY on this somewhere but by all means talk to the shop first.

TMAllison · #7 07-13-2008, 01:49 PM

Another member with a W210 has had the reversed fan issue with eBay (chinese) fans.

On that chassis the harness can be reversed IIRC.

p. rex · #8 07-13-2008, 02:35 PM

Okay, well, if the thing about the Chinese fans is true, it is still not acceptable. That means the mechanic used a substandard aftermarket part without telling me; if he can reverse the polarity on the harness, great; if he can't, then it still needs to be made right, and I am assuredly NOT paying for it, beyond perhaps the difference in price between the cheap Chinese fan (assuming that's what it is) and an OEM fan.

For what it's worth, the fan does not match the original one on the other side; the "cap" on the front is black instead of gray, and there's an exposed metal bit in the center.

Matt L · #9 07-13-2008, 02:41 PM

I had a cheap knock-off fan on my car that I purchased from some ebay seller. It was wired in reverse. I reversed the connection and it then worked for the next nine months. After that, it would no longer start if the car was sitting still. Now, when do I need that fan again? Also the power was severely diminished. I suspect cheap magnets were used that lost their charge.

The 124 has a simpler control circuit, so this is unlikely to cause your fan to fail to start. However, if the problem with mine was cheap magnets, that would affect your system (in time).

If it was a cheap aftermarket part used in there, and you didn't agree to this, you should definitely want satisfaction. How to get it is another story.

duxthe1 · #10 07-13-2008, 03:07 PM

I've seen it on the Bosch replacements too. The connector only plugs in one way but the wiring can be switched in the connector. Some techs assume that they are always correct in the connector, but experience has taught me to check every time. To fix the problem you have to take the connector apart and swap the wires. Unfortunately the connector is under the aux fan shround.

platt-deutsch · #11 07-13-2008, 03:51 PM

Be sure it is actually moving air in wrong direction. Maybe the blade pitch is opposite and it needs to turn the opposite way ?!

Arthur Dalton · #12 07-13-2008, 04:33 PM

Quote:

Originally Posted by platt-deutsch

Be sure it is actually moving air in wrong direction. Maybe the blade pitch is opposite and it needs to turn the opposite way ?!

Correct fan motor direction can be checked by simply looking at the Fan Direction Arrow on the fan hub... the arrow is stamped right into the front of the hub...........

Martin Wolf · #13 07-13-2008, 06:34 PM

Arthur,

As usual, insightful and to the point. I just posted about our 300 e which overheats when AC is on. After reading your post, how simple it was to go out, jumper the press switch leads and watch both fans spin opposite the arrow directions. These were real ACM fans not e bay specials.

Unbelievable, the connectors are not reversible, so how can they go backwards? This really explains the overheating when the AC is on, ie. the aux fans must kick in, counteracting the engine mounted fan, and things go from warm to hot. When the temp climbs higher and the aux fans go to high speed, it actually makes things worse.

Wow, what an eye opener.

Thanks,

Martin Wolf

Arthur Dalton · #14 07-13-2008, 07:18 PM

W

Yeah...so many are coming non-polorized that it is best to hook them to a battery before install just to see beforehand.

Some of these are used on other makes and do in fact call for opposite rotation then Benz does .. [ I think BMW spin the other way and use the same fan motors]..You would think they would have an installation warning notation on them.................Tab A goes into Slot D....

duxthe1 · #15 07-13-2008, 07:19 PM

If both fans are running backwards then you have the lucky option of reversing the wiring in the aux fan connector nearby the receiver drier. The connector just clips together and can be pried apart with a little coersion. Once it's apart you swap the wires and clip it back together.

When only one fan spins backwards reversing the wiring there doesn't help. It has to be reversed at the pigtail coming from the individual fan which is under the fan shroud.