I have a 2003 r53. I have put it back together last week after a fatal spun bearing, as documented on an earlier post, only to discover the cooling fan is not cutting on. This means the car is on, running, and then the temp starts to creep up. I can watch the needle, the fan never turns on, and the temp will hit red, i even tried turning on the a/c, this is supposed to force the fan on, but nothing happened. Now in full disclosure the ac is not charged, meaning it has no Freon in the system, i just hooked everything back together last week and discovered the fan issue on the very first engine crank.

So based on research from the NAM forum i have done the following steps.

1. due to old wiring loop ( my dealer never added the separate wiring to the power steering fan as best i can tell) i have tested the pwr steering fan. It appears, on bench test, to still be operational, however when the car is running it does not turn on either

2. check all fuses in both boxes, including the 5amp that controls cooling fan. Everything meters out to completed connection

3. head temp sensor, getting reading on dash gauge so temp sensor in head seems to be operational.

4. check coolant to make sure no air is trapped. Used bleeder screw open until coolant flows out of bleeder, as described in bentley manual. Seemed to hold steady on coolant level. (will try the start engine with cap open cap and bleeder valve open until fluid comes out of bleeder method) but system is not leaking nor can i hear any escaping air

5. check lowspeed relay, will do bench test tonight

Now here is where i have issues. The Bentley manual only shows the MCS diagram for the post single loop issue with pwr steering fan. This is the one where they have seperated the systems. So does anyone have the proper pre march 2003 build date wiring diagram as it left the factory for the engine cooling system? I am trying to diagnose why my fan does not turn on at all, instead of ordering a $280 part that may not be needed, i would rather diagnose before ordering.

any additional feeback, or wiring diagram would be helpful,

joey
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I am still looking for the cooling system pre production 2003 wiring diagram. Since my first post on this issue i can report that the fan is operational in Hi speed only. By passed the relay, and jumped powever to the fan, low speed work with no issue. So it is the control wire from the ECU and why it is not sending a ground to the relay.


Looked at both wires from the ECU as shown in the diagram from Bentley. One is Brown and yellow, and one is Brown and green. The brown and yellow (high speed) Brown and green, do not know but it did not send to the post as shown in diagram/

Please help, no low speed.

 

hi there is and plug just before the radiator that look like the part2 on the diagram look inside and do some test it hapen to me...