BmoreCherokee

98 Cherokee - AC is not cold. tried to recharge, however the low pressure guage is reading 85 - 90. compressor cycles on and off.

I have a 99 Cherokee that has good cold AC. The low pressure guage reads between 40 and 60 (as the compressor cyles on and off)

any suggestions?

Bustedback

You need to evacuate the system and vacuum it down to 30hg for about 15 minutes to boil out any moisture, then charge the system with the proper amount of refridgerant. But before you do all of that, you need to find the leak and fix it.

BmoreCherokee

pardon my ignorance or stupidity, but I've never really messed with AC before. why would pressure be so high if there was a leak?

Bustedknuckle

Theres a high side and a low side to A/C systems. If the low is too high, it's high for a reason, being theres a leak (or a component failure, i.e condenser, expansion valve, etc. Using either a UV light, or sniffer, and permitting the system has dye in it, find and correct the issue. Then continue on with Bustedbacks' advice.

Bustedback

Because the compressor is not on long enough to pull the low side down. When the A/C is not in use both the hight side (pressure) and low side (suction) will equalize. So if the compressor is only rapid cycling, the suction side will not be pulled down and the pressure side will not go up. Now you ask why would the pressure be high if there is a leak? The leak may not be enough to lose all of the refridgerant, there could be air in the system, and there could even be a restriction someplace.