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Roy Belding
Roy Belding, ASE Certified Technician
Category: Pontiac
Satisfied Customers: 5740
Experience:  Master ASE since 1980
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Pontiac Grand Prix GT: Im having the same issue on my 97 grand

Customer Question

Im having the same issue on my 97 grand prix gt im fairly certain that i got all the air out of the system when i unplug temp sensor fans turn on, also when i run heater on hi and defrost the fans come on frequently. So from that i gather the relays are good and ive checked the fuses they are all fine. Heater blows hot and ac blows cold so im just not understanding what the issue is i replaced upper and lower intake manifold gaskets oil is new and clean. I dont have access to a computer to hook up to it would it be a bad idea to just bypass and run direct power from lights to the fans and drive it
Submitted: 1 year ago.
Category: Pontiac
Expert:  Roy Belding replied 1 year ago.
good afternoon my name is ***** ***** I will assist did the car overheat??does the fans come on by themselves when the ac is turned on???have you replaced the temp sensor?? do you have a scan tool to look at live data?? Roy
Customer: replied 1 year ago.
I stated all that information in my original question i didnt spend 27 dollars to be asked what i already told you. New: temp sensor, upper and lower intake manifold gaskets, tstat, radiator, water pump. The fans have power they turn on with the ac
Expert:  Roy Belding replied 1 year ago.
I am trying to get some back ground on the original issue. if you are not willing to answer my questions, I am out. it is the only way I can help from here, not being there. will you answer my questions????
Customer: replied 1 year ago.
I did. But originally bought rhe car and it would get warm like 3rd hash on temp gauge warm at an idle or stop light and such so i figured it was a thermostat issue so i replaced that and bleed the cooling system and the problem still continued so the next thought i had was that the water pump was worn and weak since it seemed that at higher rpms it would stay cool i figured the waterpump was moving more water so i replaced it and belt tensioner pully and assembly along with the heater core elbow that went with it and again bleed the system and the problem continued and through research i found what lead me to the lim gasket so i did the lower and upper gaskets and all that went with that and again bleed the system it pressurizes and the problem is still there so yesterday i didnt the temp sensor and relays and checked fuses bleed the system and it still continues its just fine when driven with ac on but cant do that all the time
Expert:  Roy Belding replied 1 year ago.
ok, after the thermostat replacement, did the temp increase on the gauge??? it needs to heat up to about 212 to turn on the fans. will it overheat if you dont use the ac??does the fan work with the ac turned on as I asked before??? you have covered most of the bases here. the fact that when you remove the sensor wires tells you the circuit is working and there are no issues except possibly the sensor or the connector. make sure the connector has no damage or loose pins. do you have a scan tool to view live data?? remember, I have been paid nothing. only when you accept my answers do I get a small portion of what you were charged. please do not think I was paid anything. I will stay with you until we find something here. Roy
Customer: replied 1 year ago.
No after replacing the thermostat it was the same temp.
Yes both fans turn on with the ac on.
Without ac on it climbs up to the third hash on temp gauge and i always shut it down to prevent possibily damaging something else.
When i replaced the sensor i did replace the clip that connects to it as well cuz it seemed to the wires on the old one were loose. And they still dont turn on by the time it reaches the third hash mark unless i disconnect the the sensor then they turn on and when i reconnect it after they are running to be able to see temp on gauge it drops down to the 195 and the fans will turn off and not turn on again until sensor unhooked again or ac is turned on.
No i dont have the ability to hook uo to a computer or scan tool but i do have a infared thermometer that i used to check the temp while the sensor was disconnected and running i let it run for well over an hour and it would only get to about 215 and drop down to the 195 but i just dont like the idea of the gauge not displaying the temp while driving but to me it seemed fine
Expert:  Roy Belding replied 1 year ago.
it does sound fine as you say. do you not believe the guage reading??? is that what you said toward the end??? Roy
Customer: replied 1 year ago.
No im pretty confident the gauge is reading correctly only cuz its saying the same as the one i replaced and still acting the same. The car runs great and doesnt even get warm when ac is on or if i disconnect the sensor which to me means something is wrong to where the fans are not told to turn on at the set temp and really idk if its worth replacing the pcm for just that if everything else seems fine. Idk ive read that people have put a switch in for the fans to turn on but to avoid the risk of forgetting to turn them on i was kinda thinking of wiring it to something else that turns on automatically when car is started
Expert:  Roy Belding replied 1 year ago.
the gauge unit does not get its signal from the sensor you replaced. separate sensor for that. the coolant sensor sends a signal to the pcm and based on that signal, the pcm turns on the fans by grounding the relays. with you disconnecting the sensor as you did, you verified all the wiring is in good shape. the only thing remaining is the sensor and the connector. it is possible you have a bad new one as well. we have all been fooled by bad new parts. Roy
Customer: replied 1 year ago.
Yea ive had such problems with new parts as well but my infared reads the same as the gauge does. I didnt know that the temp sensor didnt tell the gauge what the temp was. So why does it drop when i unhook it to turn the fans on? And come back when reconnected? So my assumption of the pcm is probably correct and to fix without replacing the pcm is to bypass wire the fans?
Expert:  Roy Belding replied 1 year ago.
please dont froget to rate me as it is the only way I get paid for my efforts Roy