I have a 1996 WS6 M6

So this morning I had my cooling system completely flushed. They used the machine to flush out all the dexcool crap. Used the green stuff to refill, and also replaced the thermostat with a stock one from OReilly's. Well now my heater finally works great.

But now the fans will not come on when the car gets hot. If I turn on the AC or heat/defrost, they will come on. But idling, slow traffic, the car will just keep rising and overheat. Took it to autozone and it is throwing codes 1641 and 1642. Already checked the relays. Also, if I turn the AC on, and the fans come on, if I turn the AC off, the fans will keep running for a little while. Please any help with this matter is greatly appreciated.

Thanks

 

Those are both fan faults for ALL the relays. First the codes should be reset and see which ones return. They are from history and it sounds like at least one has gone away from the what you describe. Second, the PCM should be scanned to see what temperature it is seeing. It could be seeing a faulty sensor and not actually measuring the correct temperature.

Don't drive it unless you have the AC on causing the primary fan to run all the time.

FYI the faults you listed are an indication that the PCM did not see the proper voltage at the line that turns on the relays. The PCM grounds one side of the coil (the other side is hot all the time) to turn the relay on. The PCM monitors the line to the relay coil to be sure it is at 12 volts prior to activating it.

The 2 lines in question from the PCM to the relays are as follows:

Dark green wire from the red PCM connector pin 11 through connector C100 to relay 1 in the underhood fuse panel.

Dark blue wire from the red PCM connector pin 10 through connector C100 to relay 2 and 3 in the under hood fuse panel.

C100 is the black 10 pin connector located right near the PCM.

 

Replaced the coolant temp sensor in the water pump today. That seemed to fix the problem.