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Yikes ordering a PCM to fix a cooling issue... did you verify the signal for the fan relays isn't coming on? This sounds like a highly unlikely root cause. The PCM hardware is robust and not really known for randomly blowing outputs.
im not fully convinced that’s the problem but I’ve gone through everything else
Everybody has been very helpful, This has been a real pain to diagnose
Thats one of many reasons this forum ROCKS. There seems to always be somone that has ideas, info and experience with just about anything that could happen to a C5. Toughest nut to crack seems to be the nasty no longer produced hard to repair early year EBCM's.
im not fully convinced that’s the problem but I’ve gone through everything else
I maintain that on a 70 degree evening your fans should have no need to turn on. You have another issue. If you're just totally stuck on the PCM possibly being the issue, you can confirm or rule it out one way or another in 5 minutes with a multimeter. I'd still put money on your AC condenser being packed with sand and debris. The symptoms are right from the C5 textbook..
Yikes ordering a PCM to fix a cooling issue... did you verify the signal for the fan relays isn't coming on? This sounds like a highly unlikely root cause. The PCM hardware is robust and not really known for randomly blowing outputs.
I would think there is a way to test the outputs with a test meter to see if they are being triggered. Would be super helpful to have HP tuners scanner - or another scan tool with output controls like turning on the fans - so you dont have to try to reach those temps in order to test the output for triggering the fan.
Last edited by Toys4Life C5; Sep 27, 2020 at 11:26 AM.
Etc sensor is a thermistor, the higher the ETC less resistance value is sent PCM. I would probably try to simulate the high temp by using rheostat and use DIC to see ECT values. Then check if the fans are coming on in the right mode...
That is actually a good idea. We know the fans work so is the signal actually being sent to turn them on. I would follow the suggestion above and see if you can simulate the high temp by using rheostat and seeing if the PCM will send the signal to turn on the fans. It is possible the PCM is not getting the right input signal and the PCM might still be good.
Whats the highest temperature the car has gotten to? You said 235 previously, the high speed fan doesn't start until 236. Also, does it get hot when driving steadily at speeds 50+?
I agree with toys4life on the 160 thermo not being needed. Aside from what others have said, you need to ensure you have the stock air damn under the front end pushing air into the rad area. I am assuming your car is stock and no aftermarket splitters are in use, correct? I ask as some of these cause cooling issues. Make sure coolent level is correct and no leaks exist. These rads start to leak at the seams where the plastic end tanks meet the aluminium. Just the basics before you start worrying about fans, but as you mentioned it's hot while driving..
Yes it’s all stock, High speed fans do not come on at all even with the ac on
Again, I agree with previous posters about junk blocking the A/C condensor and/or radiator. Have you ever flushed the radiator? If you run Dex Cool, early Dex Cool would coagulate when run years after it should've been changed. Don't remember when this was resolved, if at all. All of these things are pretty cheap to try, compared to new PCM. Anyway, I also agree you shouldn't be close to 225° when going 70mph down the freeway, unless maybe it's thru Death Valley in early August!! In other words, unless someone has tuned the car and it runs hot at cruising speeds, the fans shouldn't even come on at a steady 65-70mph.....
Last edited by grinder11; Sep 28, 2020 at 11:08 AM.
Two thoughts on this. Read both before doing anything.
First thought: If only the right fan is coming on then I would have to think that your left fan is shorted out. During low speed operation the fans are connected in series (see first pic below) and both would come on. If one is not coming on in slow speed mode then it indicates that fan is shorted out. The other fan (right in this case) would get twice the current flow through it and it would act the same as if it was in high speed mode. If you have an ohm meter you can measure the left and right fans and see what the resistance is for both of them. Based on what you are saying, I would expect the left fan to read almost zero resistance. The other way to check the fans is to power each one individually. I would do this with a power source taken from outside of the car, preferably a battery charger. Reason for this is if you do have a dead fan you might want to limit the power flowing into the fan if it is stalled. A battery would act as an unlimited power source and the results might be interesting if you dead short a battery. A battery charger will limit current on a dead short.
Second thought: If only the right fan is coming on then it is possible the right fan is running in high speed mode and not connected in series with the left fan (see second pic). If this is the case, fuse 49 should open as the current through the shorted left fan should blow it.
I would check the fans by powering them individually and get back to us. We can help you more at that point.
Replaced Pcm no change
just noticed left fan is not turning on at all and right fan is coming on at high speed only to compensate
Again, the fans are controlled together at all times. If the left fan is not coming on and the right fan is, that tells me the left fan is bad. That will cause the low speed mode to not work at all no fans, and high speed mode to only run the good fan. Remember, there is no low speed fan or high speed fan. They always run together in low speed or high speed.
Again, the fans are controlled together at all times. If the left fan is not coming on and the right fan is, that tells me the left fan is bad. That will cause the low speed mode to not work at all no fans, and high speed mode to only run the good fan. Remember, there is no low speed fan or high speed fan. They always run together in low speed or high speed.
So after all that I guess I need to replace the obvious.... the fans
So after all that I guess I need to replace the obvious.... the fans
Its up to you, but if it was me i would replsce them both since the other is likely to fail. You can replace the bad fan and it should work properly. Before buying more parts I suggest measuring the motor winding resistance and compare the two fans. If the bad fan has high resistance or is open circuit compared to the other that is what you will want to know
Its up to you, but if it was me i would replsce them both since the other is likely to fail. You can replace the bad fan and it should work properly. Before buying more parts I suggest measuring the motor winding resistance and compare the two fans. If the bad fan has high resistance or is open circuit compared to the other that is what you will want to know
anybody know where to buy Oem complete fan assembly?
I concur. And just because you look up in the radiator intake in the bumper and there isnt a McWalmart bag in the way doesn't mean it isnt occluded. 2 years ago I had similar highway temps and used duct tape around my hand to clear out A TON of sand and pine straw and crap and it made a 20 degree difference.
I must share.....many years ago, I started to overheat. Got under to inspect and found an entire T-shirt got sucked up in the left side fan and shorted it out,..;.took out the motor, fuse and the relay.
