Question about 1998 Pontiac Grand Am

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"N" Body GM Cooling fan circuit issues

Just rebuilt top end in Grand Am 3.1L "M" My son ran it hot which resulted in blown radiator, water pump, and head gaskets. It now runs awesome with no codes. Also had to replace reservoir cap when I noticed insufficient cooling system pressure. Now if I can just get the cooling fan to work correctly he can go back to driving the heck out of it! First, the fan itself is good. And the coolant temp sensor seems to display accurate readings on my scan tool. The relay is also good. And when I ground pin 32 from PCM the fan comes on as normal. I removed the PCM and checked continuity to the relay...good. So I went to the junk yard and grabbed an exact PCM (and a relay anyways). Got home and after swapping the PROM chip replaced them both. I was very dumb founded when the fan STILL doesn't come on at an appropriate temperature. Anyone have any insight on this?

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  • Pontiac Master
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Does the fan not come on at all, or not until the temp is above 230 degrees ? And do you know if the computer is sending a ground signal to the relay at 220 degrees ?

Posted on Jul 19, 2013

  • brandolee
    brandolee Jul 19, 2013

    The fan did not come on at all on its own. However if I ground the correct pin on the relay straight from the PCM it does come on. However I did not let it go above around 217 F on my scan tool. Should it come on hotter? I thought 195-205F. Also, I could be wrong but I also thought when Air Conditioning request value is true that the computer would also signal fan and it doesn't.

  •  Stephen
    Stephen Jul 19, 2013

    The thermostat opens at 195 degrees. The system runs in normal range from 195 to 220 degrees. Once the temp sensor goes over 220 the computer should ground the relay. It happens around 225 degrees due to the microprocessor delay in the computer. The fan cuts off around 200 degrees and the cycle starts over. And yes the computer should ground the relay for the ac, but not until the high side pressure reaches 200psi or so. That way the fan is not running if the ac system is empty of freon.

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