1999 gmc jimmy

A/C worked fine last fall but the first hot days this year I have nothing. The compressor was not engaging at all so I went for the easy fix and added freon. Now the compressor kicks on for 2 or 3 seconds and then off for 6 seconds and then repeats the cycle. It's on long enough that the air from the vents is cool but not cold. At this point I have probably overcharged the system. Pressure on the low side reads 65 psi, the compressor kicks in and in 2-3 seconds the pressure drops to 25 psi and the compressor shuts off. Pressure builds back to 65 psi over the next 6 seconds and the cycle repeats. Any advice would be greatly appreciated as summer is looming! Thanks!

After thinking about it for the past couple of days it occured to me that the low side pressure that allows the compressor to kick on is coming from the attached freon can. Without the can attached the compressor does not kick on at all.

captaincheez

the pressure in the system is too low, which is causing the compressor to cycle on and off. pull the wire on the top of the accumulator(that metal can thing right before where the low hose goes into the firewall) and attach a jumper wire across the leads. that will keep the compressor on and you can add enough refridgerant.

1999 gmc jimmy

Thanks for the advice. That is exactly what I did. I also added a can with dye so I might locate any leaks. Pressure held for about a day and then was gone again. No sign of dye anywhere so I am assuming the leak is somewhere around the evaporator assembly which is between the dash and the firewall. Have not determined whether I want to tackle that job yet. Does anyone have any experience in that area? I checked Chilton's at the library and they had no A/C advice whatsoever.