2006 LS radiator fan intermittant any troubleshooting insight?

[scjmc]

2006 LS 77K radiator fan is intermittent. When I turn AC on it does not run....usually. Sometimes it will.... I have the single 4 wire fan connector. Power and ground are good, as well as the turn on wire. My understanding is that the PCM communicates with a computer inside the fan over the wh/blk wire? Is there any test that I can run to see if the PCM is commanding the fan to run? Does anyone have any ideas on how to determine if the fan motor is bad with this 4 wire connector? At times the fan will work, and the bearings seem to be in good shape.

 

[joegr]

You need an oscilloscope to see the PWM signal from the PCM to see if it is okay. Almost certainly, the PCM signal is okay. The reason I say this is that the fan has a fail-safe mode. If it doesn't see the correct sort of signal from the PCM, it goes to full on all by itself. If you disconnect the white/black wire, the fan should turn on full power anytime the key is on. If not, the fan is faulty.

 

[scjmc]

Thanks Joegr. That's exactly the information that I was looking for. I will definitely give that a try by interrupting the signal wire.