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stumped on why a/c doesn't work

big-john2450 on Mon June 02, 2008 3:37 AM User is offlineView users profile

Year: 1998
Make: cadillac
Model: eldorado
Engine Size: 4.6L
Refrigerant Type: r134a
Country of Origin: United States

i had a leak, fixed that,evac and recharged system,replaced high and low side pressure switches just to eleminate possible problem, replaced a/c relay, replaced an a/c fuse even though it wasn't blown....didn't help.

error message.......low freon a/c off........set code on computer. took battery cable off to unset code....didn't work.....bought code reader, reset code/cleared.....didn't work......out of options......any suggestions? mechanic that evac system being jurk.....says he did what i asked and system is full of freon.....doesn't know why system won't come on...don't want to take back to him. dealer offers a diagnostic option charges $45 for 1/2 hour.....don't mind paying money but dealer doesn't guarantee can fix....don't want to throw money away for nothing. heard it might be possible to bypass low pressure switch to MAKE the compressor to work....would this help? long term fix? could it be possible to hook up a toggle switch to override the computer controlled a/c system? running out of options.....been doing the two window 60mph and sweating alot.....ha ha.

any help appreciated.

big-john2450 on Mon June 02, 2008 2:42 PM User is offlineView users profile

i,ve tried to jump the low pressure switch and reset the code but that didn,t work, so i have decided to try and hook the compressor directly to the battery. when i disconnected the hookup o noticed that someone has put a jumper across the two connectors and them plugged it in, would that disrupt the signal? isn't one of them a ground?

mk378 on Mon June 02, 2008 3:20 PM User is offline

Do you still have the error message? One of the GM experts here would know more about what to do about it.

The thing on the compressor plug is probably a diode, standard equipment from the factory. Measure if you have voltage at the compressor with everything plugged in and running. If the low pressure switch is a 2 wire unit you can test it for continuity. It should be closed at normal pressure with the compressor off.

Be very careful jumping the compressor to the battery because you will have no protection against over pressure, under pressure, etc. The rest of the car will not know that the compressor is supposed to be on and it may not turn on the cooling fans. I would suggest doing it only with the engine stopped just to be sure the clutch plate pulls in. There should be no need for toggle switches etc.

GM Tech on Mon June 02, 2008 5:16 PM User is offline

Your diagnostics are free- right on the car info center-- you can pull the codes yourself-- hit "off" and "warmer" at the same time- then use fan "speed up" for yes and "fans speed down for no to check ACM codes f any- what is the code? the ECM is most likely keeping the compressor off and the code is immediately resetting when battery is re-hooked up

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......

big-john2450 on Mon June 02, 2008 6:48 PM User is offlineView users profile

another update,

since jumping the low pressure switch didn't work i decided to bypass everything and hook the compressor straight to the battery. so i got everything ready started the car and then hooked up the compressor, the clutch jumped right in then i hurried around and got in the car and reset the code with it running. it stayed on for about 5 minutes then reset the code, but the compressor was still engaged so it stayed cool. so i turned off the car and checked the freon level and it was really low, so i jumped in my wifes car and went to the auto store and bought a can of 134a, came back hooked up the can, started the car jumped the compressor again and it sucked the can right in, turned off the car, checked the freon and its right on the mark...full. restarted the car, jumped the compressor, reset the computer and it stayed on about 5 minutes and set the code again......low freon a/c off, but the compressor was still running and it was still cooling but now its cool on the drivers side and heat coming out the pass. side vents.......i'm stumped!

Chick on Mon June 02, 2008 9:53 PM User is offlineView users profile

You can't use those micky mouse gages to check your pressures, and the compressor must be running. Even half a charge will show "full" with the engine off..Best to recover your refrigerant, pull a deep vacuum and charge the factory amount back in with some UV dye. Your compressor is throwing codes due to not being properly charged.. The UV dye will help you find your leak..Hope this helps..

Email: Chick


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