Electrical cooler fans, overheating

[VicC220]

Originally Posted by olli_m89

I have now attempted to get the fans going by disconnecting the temp sensor from the termostathouse, but the fans did not come to life.

I have attatched some images, one is of the control module inside the driver-side wheel arch the other is the relay I think could control the fans and the third is the aux fans themselves.

i didnt touch the control module.

the air/temp sensor looks like this from what i remember

[olli_m89]

Originally Posted by VicC220

http://www.benzworld.org/forums/w202...-question.html

check the diagram on page 1. see whats goin one with yours i have a c220 and mine matches exactly with the diagram the 1st poster put up there.

So u know, when I disconnected the sensor (the one on the driver side under the plastic benz logo right above the water pully, my fans came on. but later i came to find out anyway that my relay 1 fuse was blown anyway. i dont know if it was the level 2 fan that came on, but i CAN tell u both them things was turning, and it was loud as hell, even though my relay fuse 1 ws blown. i dont know what wouldve happened if relay 2 fuse was blown as well. the fuse sits right inside of the relay as described in the link. it was a 15amp. i replaced it with 25. problem solved.

I don't have that type of relaybox, I don't have the relays for Hi/Low settings to aux fan. As I understand the cable harness for the air condition and the headlamp cleaning system is the same, I found an illustration of that here Google Translate and I have noticed that the headlamp cleaning system also is malfunctioning, the headlamps should be cleaned the same time as the windshield is cleaned, right?
But it does'nt work for me, so I think i'll have to examine the cable harness and try cleaning the contactareas.

I've attached an image of my relaybox-layout.

[olli_m89]

I have finally found the solution to the problem. The aux fan relay/controlmodule I found in the driverside wheelarch is most likely the malfunctioning part. I have attached a picture below and made an excplanation of the pins and connections on the cable.

#1 - I measured this with a voltmeter, it indicated 13,84 V and it was the same regardless of the engine running or the ignitionkey placed on 0. So this is the powersource to the module.

#2 - This was connected to the left aux fan, I tried jumping the wires from #1 to this one and the fan started spinning with full blast.

#3 - Same as #2 but for right aux fan.

#4 - Ground

#5 - I measured this with ignitionkey set on 0 and the voltage was 0 also, then I started the engine with AC on and the reading was 0,15 V but I kept reading it and after a short while it showed 10,84 V so I guess this is when the fans should start spinning, but they did'nt.

I also tried attatching wires on the #1, #4 and #5 pin and their respective contacts on the cable, then I measured if pin #2 or #3 had any voltage but it was zero point something.

So I took the module away from the car and opened it at home, there was quite much corrosion on the pins to one of the microsprocessors inside the module, so I am going to buy some electronics cleaning spray tomorrow and try cleaning the module to see if it works.

For now I have an on/off switch inside the car that controlls the fans, it is fused with a 15A fuse (The fuse in the fusebox is 30A and I replaced that with a 20A fuse just to be safe.) this is because i'm getting tired of the whole sauna experiense when driving in stop and go traffic, I allways have to turn the AC off and turn the heater on full heat.

Thanks for the help everybody, I will report if the electronicsspray helped at all

[bmeister]

Glad your close to the conclusion on this. Water and electronics don't mix well of course, especially in a wheel well B

[Bimmerman4ever]

I don't have an overheating problem though my aux fans pulse on and off and turning AC on/off doesn't effect this condition.

I have been trying to diagnose as you have.

My relay, fuses, and modules are set up the same (96 C280)

It could be the aux fan control module, but what would indicate a failing water temperature sensor/sender?

I was hoping it was that since the WTS is $21 and the FCM is $150


Are you saying that the relays are not part of this circuit?
(I though maybe the pink or silver relay maybe the problem)

YouTube - 96 W202 pulsing aux fan

[Bimmerman4ever]

FYI for anyone
I had gotten some more info on the relays:

Pink color 0015427419 Air Injection

Silver color 0015420219 Headlamp, Wiper/Washer, Alarm System, O2 sensor, Immobilizer

Oh by the way, the long black module with the lock lever on top in the relay box 2025420132 is the Lamp/Light Control Unit

[Bimmerman4ever]

Found out what was causing the aux fan pulsing

AC Pressure Switch; On Receiver Drier; 3 Spade Connector



Denso P/N 1408300072



I know I have to drain the refrigerant before replacing anything on the AC system. Since I already have a new dryer (acts like a filter for the AC system), all I need is the AC temp sensor (which also mounts to the dryer with the pressure sensor) to make it complete