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Rad Fans Not Coming on Engine over-heats

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Old 09-02-2012, 04:20 PM
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Because of the access heat build up from the a/c system. I suppose the cooling system has yet to be flushed either.
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Old 09-02-2012, 06:10 PM
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What ??????????
Old 09-02-2012, 06:30 PM
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Originally Posted by rolm
Why do you think its the stat If the stat was closed then the engine will over-heat even with the ac on. I just bought this van so I have no idea if the stat was ever changed. My guess is due to its location I bet it was never changed.
Maybe I got confused with what you said.
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Old 09-02-2012, 08:19 PM
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I watched a video on YouTube on how to replace the stat What was GM thinking or not thinking maybe that is why the went belly-up. The vedeo was very detailed bet it would take at least 4 hours for the dam job.

I do not believe I need a stat change I am thinking the PCM is sick. If I do change the PCM what will happen to the odometer kms will it read the new/used pcm'* kms
Old 09-02-2012, 09:03 PM
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What'* making you think something is wrong with the PCM?
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Old 09-03-2012, 08:51 AM
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Well If the fans work normal with the AC on then I would have to assume 1) the temp sensor is not giving the PCM the correct reading or the PCM is not sending the correct info to the fan relays. If I were a betting man I would say the PCM is the sick one hear. But before I replace the PCM I will replace the temp sensor 1st due to cost.

As I stated in my other threads I did have the same problem on my 99 olds and in that case I did replace the temp sensor with no luck. I trade the car in with the sick cooling system.
Old 09-03-2012, 10:16 AM
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In order to verify if it truely is the pcm or temp sensor, you would need to connect a scanner to the car to verify what the pcm is seeing for engine temps. On our bonnevilles, the low fan wont kick on until 212f and the high fan at 226f.
Old 09-03-2012, 10:38 AM
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Can anyone tell me what fan relay and the pin # where I can connect a ground to keep the fans running at low speed. In this way I will not be messing with the PCM'* operation.

Up to this point I am convinced that the PCM is not sending the proper ground to the low speed relay.
Old 09-03-2012, 10:41 AM
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Originally Posted by Mike1995
In order to verify if it truely is the pcm or temp sensor, you would need to connect a scanner to the car to verify what the pcm is seeing for engine temps. On our bonnevilles, the low fan wont kick on until 212f and the high fan at 226f.
I do not have a scanner. Here in Toronto the dealers charge from $115 to $165 for a quick diagnostic.
Old 09-03-2012, 11:46 AM
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Obviously the pcm is turning the fans on either when the a/c is called for or when the temp sensor is disconnected. So, with those 2 tests completed and working correctly, then any mechanic would tell you that the pcm is fine.

Your next step is to either replace the thermostat or the temp sensor.


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