94 E420 - Driver Side Aux fan not engaging - PeachParts Mercedes-Benz Forum

wjm · #1 05-12-2004, 04:06 PM

Folks,

Car started to overheat today. I opened my hood and had some "smoke" coming from back/top side of engine (sort of in front of firewall). Anyway, after some investigating I noticed that the driver side aux fan is not engaging.

Question... Is there a fuse or relay that controls just the driver side aux fan? Anything else I can do to test or check?

wjm · #2 05-12-2004, 07:24 PM

Another question.... Should the car overheat when 1 fan is inoperable?

wjm · #3 05-12-2004, 08:26 PM

Quote:

1) spin the fan by hand without any power. Does it spin freely?

Yes it does. No problem there.

Quote:

2) disconnect the offending fan by removing the connector. It could be hidden behind your bumper. Apply 12 volts directly. Does it spin?

Well, finding the connector is tough. I might have to take off the front bumper to get to it.

wjm · #4 05-13-2004, 08:51 AM

Well,

Taking the advice from some folks here, the first think I did was to give the fan a whack. It worked. Acually, I'm finding that both fans are shutting off independantly and randomly, so I assume that the brushes are wearing out on both of them.

Guess I'll have to replace them. Has anyone replaced these? What is entailed?

MrCjames · #5 05-13-2004, 10:39 AM

Quote:

Originally posted by tkamiya
If this is W124 E420 (which it is), both fans are connected in parallel without any fuse.

The fan(s) should be protected by fuses which are inserted into color coded relays inside the fuse panel. Beneath the cover there should be a Blue-15A, and a Green-30A. Perhaps you were eluding to the fact that the fans are not independently protected.

The running hot can be a combination of factors which at this point require the process of elimination.
1)it sounds like one fan is in need of replacement,
2)reassess the running hot after the fan(s) are installed
3)if your engine temp stays at 100C email me for a cure

The smoking at or near the firewall would lead me to suspect a leaking valve cover gasket.

wjm · #6 05-13-2004, 11:15 AM

Only saw the steam when it was overheating. I'll keep a close eye on this.

I do have a coolant temp hack (pigtail with resistor) in place to turn the fans on earlier. Is this the fix you are alluding to?

So... how hard is it to change the fan?

Jim Anderson · #7 05-13-2004, 12:25 PM

Except on a 190E. Only one of my fans was turning, sometimes it would spin a little when I banged it. I took it out and apart and it turned out the brushes were stuck, All I had to do was un-stick them. I don't know how your car would be, but for me taking them out wasn't too bad, I did have to take the bumper off.

But be careful, take the temperature sensor off first. The weight of the bumper is a lot more than the temperature sensor wire can hold

MrCjames · #8 05-13-2004, 02:22 PM

Hi tkaimya

Given the context, Agreed. Perhaps it may have been a bit unclear for some visitors so I was adding a few details so somebody would not get the wrong impression.

B-