My van with the 5.0 liter engine puts out just a semi cool A/C air so I hooked up my automotive A/C gauges to the system and here is what I got:

High Side 105 PSI

Low Side 75 PSI

86 degrees F ambient temp with 60% humidity

I consulted a chart and found out my high side pressure should be 140-235 and suction pressure should 19-39 PSI. I am particularly worried about the my very high suction pressure of 75psi. Any ideas what might be going on here?

 

Make certain both manifold gauge valves are fully closed, first. Leaving them partially open will cause similar readings.

Otherwise, it sounds like a very weak compressor. Verify the pressures equalize when the compressor is turned off, just in case the gauges aren't accurate.

At that ambient temp, I'd expect around 40 psi on the low side and around 200-225 on the high side on a properly operating system.

 

Thanks for the reply. I checked the pressure with the system off and readings where about the same when equalized. So my gauge is good. So you think it's a bad comp? What if I just add some more refrigerant?

 

I think it's a either a bad compressor or a slipping clutch (maybe...).

Adding refrigerant is a waste of time. You already have enough in the system and the symptoms are *NOT* of a low charge.

I just replaced the compressor in mine two weeks ago for the same reason: Insufficient pressure differential.

 

Thanks for your help. I'll just drive with the windows open as I don't have the time or money for a compressor replacement.

 

Yeah, I know what you mean. My old 98 Conturd needs a new compressor and an electric cooling fan replaced. I hate spending more on parts than that car is worth! I just roll the windows down in the afternoon.

 

An update to my A/C problem. Last month I had a mechanic check the system pressure and he found the system to be undercharged so he added refrigerant and it blows slightly cooler air now. When I am moving down the highway or it is raining outside it blows coolest but still not quite what it should be. I am thinking the condenser isn't transferring heat like it should? Any ideas?

 

Still might be any of several things (weak compressor, insufficient heat rejection at condenser, etc).

What are the operating pressures now?

 

I don't have access to gauges anymore so I couldn't tell you.

 

Without pressures, you might as well just guess.

 

You are right, you need the gauges, to tell you what's going on, the one problem with 134A is It doesn't give it's heat off fast enough to provide proper cooling while idling or low speed driving, since the system was low did the repair shop pump down the system and vacuum it for at least an hour, moisture in the system could cause problems to, the water in the air freezes up at the orifice tube giving you poor performance. lots of guys just throw in the gas and run, Did they look for a leak? Put any dye in the system and tell you to come back for a blue light search? You can get the system running better if these steps were taken. Evacuating and vacuum the system is easy to do but you need the equipment, you can do a quick leak check by using a bright LED flashlight and check all the connections, the condensor, a rock thru the grill happens often, check around the compressor, your looking for oil, or dust stuck around something, refridgerant oil is clear but it makes a mess cause everything sticks to it, thats why they use the dye. Check everything you can, rub your hands along the lines, make sure there is no rubbing or chaffing, you cant check the evaporator unless you have big ***** and willing to take it apart, alot of times leaves, pine needles get past the cowl and drop into the a/c heater case, and that causes the bottom of the evap to rot. It's always wet and if the drain plugs up you can get so much condensation it will flood the passenger carpet. Thats my 2 cents Good luck.