E430 Auxillary fan?
 

My axillary fan doesn't seem to be kicking in. While idling around town today I noticed the temp creeping almost up to 100. I checked the service records and the axillary fan belt was replaced last year, so I'm guessing it was checked at that point. I checked the fuse and it said that it could be fuse# 20 or 41. I found 20 and it was fine. I can't for the life of me find #41. Checked all 3 fuse boxes I know of but don't see it. Any ideas??

Engine must reach 107C or a/c pressure must reach 16 Bar for aux fan to come on.

Really? My W140 and W124 both used to come on around 90, I just figured thats how they all worked.

If your 124 came on before 105/107C , then someone had added a mod resistor to the sensor [ common upgrade] or you had a bad [ out of calibration/spec.] sensor.

..or you are confusing high/low fan circuits..

There's a very good chance I'm confusing high/low fan circuits, because I have no idea what that means. I all I know is that the dual electric fans kicked on at around 90.

From what I'm understanding here the electric fans on my E430 don't kick on unless it reaches 107c or the a/c is on right?? It hasn't gotten that hot and my a/c is currently stuck in econ mode so there's probably not a problem, right?

How hot do these E430's usually run? The only time i remember my w140 getting over 80 was when the thermostat was stuck. Is it normal for a E430 to creep up to 95?

<<There's a very good chance I'm high/low fan circuts, because I have no idea what that means. I all I know is that the dual electric fans kicked on at around 90.>>

What it means is the 124 fans have 2 speeds , so if you had a fan on at 90C, it was a low fan and it was triggered by the a/c high pressure switch, NOT the coolant temp..you just happen to notice the low fan come on when the temp was 90C, but the 90C had nothing to do with the fan coming on...if the HIGH speed fan came on, then it would have to be triggered by the coolant temp and that would have to be 105/107C coolant temp...[ or you had a bad sw.]

So, the 2 fan speeds are different circuits , but those circuits share the same fan motor..Low fan is for a/c system and High fan is for engine temp.
It is a common misconception . The easy way to tell which fan speed is engaged is to turn the a/c off..That eliminates low fan activation on 124.

Auxillary Fan BElt Replacement
 

I just noticed that one of the auxillary fans on my E430 was not working, and that the belt which drives this fan was missing. The other fan seems to work fine. I would appreciate if somebody could explain the proper way of installing a new belt.

Thanks........Highwater

Roll it on the pulley while you turn the fan.

It's easier to get the belt on if you unbolt the motor or idler from the frame, if you are afraid of stretching the poly-V belt.

Thanks Matt. I just tried to find the pulley for the belt. There does not appear to be any. Is it possible that the second fan also has its own power motor?

Thanks

Have you removed the fan assembly from the car? The pulleys are on the back, next to the condenser.

Thanks Matt & Arthur, I was wondering if I had to remove the complete assembly, and now I know that's what needs to be done.

Very much appreciate the advice.

Highwater