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a/c works but no cooling fans

joe_mn on Mon May 26, 2008 11:52 AM User is offline

Year: 1999
Make: pontiac
Model: grand prix

clutch would not engage. i added 1oz and it turned on but the cooling fans do not run. there are 2 fans. pass side and driver side. both seem about the same size. does 1 or both run for a/c operation? checked fuses. there is a relay for #1 and #2 and cooling main. there seems to be a lot of relays and fuses and a a/c diode also. check wiring for voltage at fan with a/c on? which fan?

joe_mn on Mon May 26, 2008 9:56 PM User is offline

i unplugged the temp sensor and the fans run. the system did suck in almost a full can of freon but no cold air from the vents. time to check system pressures. how well does the compressor have to work to suck in a can of freon?

GM Tech on Mon May 26, 2008 10:19 PM User is offline

GM "W" cars "wait" on head pressure to turn on the fans--- must have 175 psi discharge pressure toactivate the fans-- this is so fans are not on while driving down the road- they are not needed until head pressure rises-- most all other GM models have fans on with a/c command-- but not "W" cars as your GP.....

So what is your high side pressure? probably not enough yet to turn on the fans----add in the correct amount and the fans will come on when needed.....

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

joe_mn on Sun June 01, 2008 7:20 PM User is offline

well i thought it worked. its my kids car and she said it seemed cool on the road. i put a gauge on it today and at idle it was 125 high so i hooked up my can of 134a and it started to rise. the gauge got up to 175 in about 2 mins and the fans did not turn on. there is no cooling from the vents. i did not check low side pressure. she had to go to work. the compressor is on, but no fans and the high side is 175+.

GM Tech on Sun June 01, 2008 11:32 PM User is offline

175 psi is not scary-- not too high-- keep trying it- there may be guage errors- Now if you told me 250 psi or more and no fans then I would be concerned- you can "jumper the relay" as a test if you want to prove fan motors are okay or not--

Low side pressure would help as well.......

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

joe_mn on Mon June 02, 2008 7:27 AM User is offline

well the fans do run if i unplug the temp sensor. i made them run initially when i added almost a full can of 134a. that made no difference in cooling. in fact, i think i had no cooling at the vents. so if the compressor engages and i can make the fans run and the pressure is not too high to indicate a blockage, and i have some 134a in the system, why don't i have any cooling? still to low on charge? maybe have a shop check it out.

mk378 on Mon June 02, 2008 9:47 AM User is offline

You have to have the full proper charge in. Note that if its undercharged so the fans haven't come on, the high side will go up higher than you expect.

If it's leaked down until the clutch won't engage at all you can assume you're starting with zero in the system, maybe 6 oz at the most. Of course if you don't fix the leak it's going to leak out again.

joe_mn on Mon June 02, 2008 4:28 PM User is offline

my comp. seized on my 96 intrepid a few years ago. i put on a used compressor and threw in 1/2 can of 134a with no evac and i got cool air. but thats a dodge. the pontiac worked fine last summer/fall. yes, leaks do happen. i think a shop could find the leak if there is one and than i can decide how to proceed.

joe_mn on Sun June 15, 2008 10:20 PM User is offline

i have a leak. the clutch would not engage. i got it running and added 1 can of 134a. i watched the pressures on the high side. it went up to 200 than the fans finally came on and it dropped down to 125. the fans would come on/off as it hit 200 and each time it would drop less. the next time it dropped to 150 or so, than 175 and now it seems to be holding at around 200 and the pressure does not drop. the vents seem cool/cold. are there any common places for a leak on a 99 grand prix?

mk378 on Sun June 15, 2008 10:30 PM User is offline

It's a V5 compressor, they are prone to leak at the case joint or the shaft seal. Do you have UV dye in the system? If you use UV dye the system must be fully charged and running for the dye to come out of leaks.

joe_mn on Mon June 16, 2008 1:15 PM User is offline

no, i have not put in dye. i have another GM car with a bad compressor and am debating buying a vacuum pump so i can swap out both units. i could buy the tools for less than a shop would want to change both compressors.

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