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I bought the car last month, from probably not a very honest seller. When I bought the car there were no problems on the instrument cluster. I did not notice that the cooling fan didn’t spin. A few days later the seller brought the car to my house. When I started the car I noticed a fault. I had a coolant icon on the dash. I checked the coolant reservoir and it was full. I also noticed the aircondition was not getting cold, but warm
After a few days I had the time to use my xentry and I scanned the car. Thermostat line interrupted and cooling fan discontinuity of signal line. I checked the cable from the cooling fan and it was not inserted. I saw a little bit of corrosion. I cleaned it and after it was clean I connected it with the fan. The car was off and the fan started to spin, but after a few seconds there was an electric shock and I could smell a burn. I think I blew the fan up? Now I don’t know what to do. If I buy a new fan, which is very pricey I have the risk of blowing it again. I checked the voltage of the cable like xentry told me and with or without ignition I get 12 volts between pin 2 and ground.
there is a lot of oddities with the cooling fan, ECU issues and air con not working... its common the fan runs at very high speed even with the key out and doesn't stop ever - when the car thinks certain fault conditions are in play
what these are and why is not well understood, very little we can do from here...
The connector was corroded like this. Can it be on full blast (I think my fan is broken but when I put a new fan it will be on full blast) if the thermostat has an open circuit?
not an expert on this particular situation - catches lots of owners and garages out
bare in mind I'm just finding stuff - on merc not necessarily your model - found these on a UK forum it has quite a few knowledgeable people
A critical difference that can help.
Fan issue - radiator logo "Coolant visit workshop! "
Coolant low - radiator logo "Coolant, check level!"
If its "coolant, visit workshop" it sounds like the fan controller is starting to fail.- the fact it was disconnected and when you connected it it ran then something went pop might point to this ?
Its PWM from a wire from the engine ecu, and it varies from a measurable 0-10V. The mosfets often blown up in the controller
there is 4 pin connector that goes to the fan and its module
1 thick(red): +12V (always on)
2 thick(black): ground
3 thin (black with red stripe) : +12V (when ignition on)
4 thin (green with blue stripe): signal wire (low voltage PWM signal)
I just got the logo, nothing else.
i checked all the cables
I had 12v on the big cable, 12v on the other cable with ignition and maybe 1 volt or so on the PWM signal wire.
I have to check again if the 12 volt goes away when there's no ignition. I want to check the cables for continuity. Were can I check that on the ECU?
If everything is good, the fan is just bad?
Also, do you know where the thermostat is located on the OM629 engine? I have a lot of experience with the OM642, but the V8 is new to me.
07-31-2023, 08:24 AM
W221 Cooling fan problem OM629 420 CDI
