Aux Fans drawing too much current - PeachParts Mercedes-Benz Forum

zafarhayatkhan · #1 05-22-2004, 06:55 PM

As soon as the Aux fans go into high speed mode, the 30 AMP fuse blows.

Replaced the 15 AMP fuse and the fans work in the low speed mode. The right fan is slower than the left.

They even blew Fuse D 16 amp but after replacement, no further problems there.

Dealership quoted $620.00 for the Aux fans replacement.

I am planning to do this myself. What is the procedure for moving the radiator back to provide access to the bolt required for removing the aux fans. Rest of the bolts should not be any problem.

zafarhayatkhan · #2 05-22-2004, 07:37 PM

It appears that the aux fans in my car must have been coming on at high speed around 95 F, because the temperature never went over 100 F.

Aux fans in low speed are unable to maintain the temperature with the car stopped and AC on.

zafarhayatkhan · #3 05-22-2004, 08:17 PM

I saw some burn marks on the resistor behind the driver side headlight, replacing this resistor maybe a first step in trying to solve the problem of the 30 amp fuse blowing.

The aux fans were replaced over a year back.

zafarhayatkhan · #4 05-22-2004, 10:29 PM

Found one other problem, looks like the relays for the high speed and low speed have been reversed.

Slot B had the Blue relay with the 15 AMP fuse and Slot C had the Green Relay with the 30 AMP fuse.

I switch the two to correct the location. As soon as I removed the Blue sensor connector, the fuse again blew in the High Speed K9 relay.

zafarhayatkhan · #5 05-22-2004, 11:03 PM

The fans are working at low speed through the resistor but blow the fuse when the direct high speed relay takes over.

Can someone verify that high speed relay has a 15 AMP and the low speed has 30 AMP fuse?

Arthur Dalton · #6 05-23-2004, 11:02 AM

K-9 [ blue-high speed- occupies slot C ] - ECT sensor activated .
Fuse rating has been increased to 25A per Benz.
K10 [green- low speed/preresistor - [ occupies slot B].
a/c pressure activated circuit..

zafarhayatkhan · #7 05-23-2004, 01:49 PM

Thanks Arthur.

Since the low speed circuit was working, I bypassed the pre-resistor, Fuse D (16 AMP) in the main fuse area blew 1 sec after the fans turned on.

Green relay with the 30 AMP fuse was fine.

Looks like, fans are bad. Spining the left fan by hand results in a few rotations, right fan stops after one.

Arthur Dalton · #8 05-23-2004, 02:24 PM

I would suspect a bad fan.
You may want to isolate each fan feed to further check it...

zafarhayatkhan · #9 05-27-2004, 04:17 PM

Replaced Aux Fans and resistor. Everything working fine. Temperature staying between 85-95 with low speed fans.

High speed comes on as soon as the connector is removed from the blue temp sensor.

The old fans were turning very slowly. Even on low speed, the new fans are very fast.

Replaced the 15 AMP high speed relay fuse with a 25 AMP. Thanks for the info Arthur.

Arthur Dalton · #10 05-27-2004, 04:36 PM

Happy to hear it is correct again.....

zafarhayatkhan · #11 05-27-2004, 06:21 PM

If the temp at some point in future starts going over 100: I will install a cool harness. Fans are a whole lot cheaper than the engine, all the electronics and wiring etc.

wjm · #12 05-27-2004, 10:06 PM

So zafarhayatkhan,

Did you change the aux fans on your own? If so, I have a pair of new ones ready to replace my current onces that (I suspect) are starting to go. Can you give me some tips on how to change them out?

zafarhayatkhan · #13 06-01-2004, 08:39 AM

Willy,

I was unable to remove the resistor bolts and the independent shop was only charging 1.5 hours of labor for both the resistor and the fans, so I had them do it.

I am taking it back to them today as they did not put back two of the bolts, 1 behind the radiator (I may have them leave that one out for ease of removal next time) and 1 infront of the fans. As is the case with most mechanics, they always think that the manufacturer installed some extra fastners!

The next time, I am planning to do this myself. It should take about an hour. I believe you have to remove 4 bolts, radiator clips, the radiator swings out and gives you access to the bolt that holds the brace. Then you remove the fans.

wjm · #14 06-01-2004, 08:52 AM

The big question is.. though... do you have to remove any of the hoses or trans cooling lines?

zafarhayatkhan · #15 06-01-2004, 08:56 AM

I do not believe that you have to remove any hoses or cooling lines.

The Independent shop would have charged me a whole lot more than 1.5 hours of labor if they had to remove the hoses and/or the cooling lines.

I'll have the tech verify that when I see him.