Originally Posted by
Padgett
Electrical and sensor issues, particularly intermittents, can only be found with either instrumentation & logging or luck. I prefer not to rely on luck
In general, I agree. One of my pet peeves is when someone has a battery that is discharging and they are told "change this", or "it's probably that". The ONLY way to address a battery that is being drained is with a damn meter. PERIOD.
IN this case, well....
Okay i will check this ... any way to test the fan module or is it case doing a swap and a see if that works .
i will test the fan with a 12v battery
You may end up swapping, but the way to do this is to understand the operation of the Fan Module (FCM), and it is a very simple concept.
How it all works:
Whey you turn the key to "ON", the ECM and FCM both power up.
1) The ECM sends pulses to the FCM, if the pulse is short, the FCM just sends a pulse back. If the ECM does not see the pulse come back, it assumes the FCM is in trouble and lights the Coolant light.
2) If the ECM wants the fan to run, it sends pulses that are longer than in 1) above, the longer the pulse, the faster the FCM will turn the fan. (If the engine is cold, but you turn the A/C on, the ECM sends pulses long enough to make the fan run slowly.) The FCM still replies to every pulse with a pulse.
3) If the FCM is bad, it won't send the pulses (not the case in your situation as you said the light goes out with the A/C off).
4) If the FCM tells the fan to run, but it senses the motor is not flowing as much current as expected, or TOO MUCH, then it fails to send the pulses to the ECM and the ECM lights the light.
I strongly suspect that your problem is a bad fan motor. Of course, if the power feeding the FCM is not reliable, that would cause the FCM to possibly not send the pulses back under load as well. I can say this, in eight years on this forum, I have seen many fan motors fail. In that time, I have seen FCMs fail at maybe 20% of the rate the fan motor fails.