I think my cooling fan controller module may be failing (read here) and I want to verify. Has anyone ever had one fail? Will the fans not coming on prevent the A/C compressor from kicking on? How can you verify its functionality? I'm guessing the PCM sends out a 5V reference to control the fan speed since it's varied in percentages based on ECT and A/C operation. The PCM shows its commanding the fans on, but they operate only when they want to. When they're not on, the car is overheating and the A/C compressor turns off immediately. I know there is a high-pressure switch in the system, but this happens immediately so it wouldn't have time to hit high pressure... thus me asking if it might be a failsafe when the fans die.

What does the service manual say to check its operation?

 

nobody ever had one of these fail?

 

I had an issue with the cooling fan in my 07. I increased the fan speed to 90% in the 192* cell for the track and didn't change the tune on the way home. Needless to say, I thought I burned up either the fan motor or control module. Well, it turns out neither were bad. The fan control module inside the PCM shorted to ground. The whole PCM had to be replaced.

I'm pretty sure this might be the same issue you are experiencing. I will say I thought the PCM was a high price item, but I believe its only $350.

I have a spare fan control module if you want to try it out.

Jason

 

you need a scan tool to check it

 

 

I have a feeling it's probably the PCM especially after reading about your problem Jason. I would think if the control module went out, or the fans, they would never work again. Now it's intermittent. A ground short sounds like the problem, but those aren't exactly easy to track.

According to the datalogs from HP Tuners, the PCM is commanding the fan on as it should, but it sometimes doesn't come on. I let the care idle up from a cold start and it got to 230 before the fan came on, PCM commanding it on in increments the whole time as expected. When it came on, the PCM showed no change, the fans just started working. I guess if the fan circuit shorted, the bus wouldn't know the difference so it really is commanding them on, the signal never makes it though.

Another issue that could be related to the PCM or is conincidence. About 2 months ago the gauge cluster was kinda wacky at start-up. It read off the EPROM version info and all the lights lit up. Instead of the full sweep on the gauges, they went in what appeared to be 1/4 increments, like a first time calibration or special mode. Maybe the PCM is just dying?

 

I feel your pain. I tried everything trying to figure out what was going on. I bought a fan control module after making sure the fan motor was still good. Once I hooked it up, no fan. I noticed the package had been opened before and thought maybe someone swapped it out and returned their bad one. I got the dealership to get me another one and same result. I had it with trying to troubleshoot it myself and took it in. It didn't take the tech long to figure out it was the PCM. He programmed a new PCM and viola it worked.

A side effect that sucked was I had to purchase another HPTuners license since the PCM code changed.

Member 8850 warned me not to put any value higher than 25% in that cell, but I figured it wouldn't hurt it for a little bit at the track. Well being lazy after the track day, I didn't change the tune out, and that spelled the end for the PCM.

I hope you get yours worked out.

 

so the failure could be caused by having the fans at too high a value for too long? I guess I should've done more research! I've had the whole table set to 90 since the tune went in in January...

 

actually I take that back. Just checked the tune, it's 25 at 192, 78 at 196, then 90 for the rest of the table. Still sounds like the PCM, but I didn't have anything greater than 25% at 192. Of course, if the cars running, the fans are on. Always. It's a hot bastard with the 427 in it...

 

Yeah, 25 should have been ok, but not sure since you say the 427 runs hotter. I'd take it in man. Find yourself a mod friendly dealer you trust and let them hook it up. The local tech here found it quickly.

 

had the same problem but I swapped the module and the fans are coming on now or at least they did when i swapped it out yesterday...