It runs great but the A/C blows warm

ANONYMOUS

MEMBER
1995 CHEVROLET S-10
200,000 MILES

It runs great but the a/c blows warm. I tried shooting freon in it butt when the clutch kicks in the gauge on the drops. Is this normal? I notice as it runs the pressure will build and drop when the clutch kicks in. I turned it off and went inside to talk with my wife for a minute. When I came back outside the guage on the can was in the red.
What do I do now? It still blows warm.

1 Reply

CARADIODOC

MECHANIC
33,916 POSTS

Be sure you're putting it in the low side. When the system is off the pressures in the low and high sides will equalize. As long as there's enough refrigerant in the system that some is liquid, the pressure will be somewhat close to the air temperature.

There's no accurate way to know how much refrigerant is in the system unless you recover everything, pump it into a vacuum for half an hour, then charge it with a measured amount. Chryslers use a sight glass on most of their models and you just add until the vapor bubbles are gone. Older Fords used a sight glass too but they still had bubbles when it was fully-charged. The best you can do is to get an approximation by the low-side pressure. It should not drop below about 40 pounds when the compressor cycles on. If you think more refrigerant is needed and the can doesn't become empty in about two minutes, place it upright in a pot of very hot water.

Be aware that professionals wear safety glasses, gloves, AND face shields. Refrigerant can freeze your eyeballs and cause frostbite.