Okay, here is the deal. This weekend it was extremely hot here (80-85). I had the AC cranking, and was pulling my 6000lb travel trailer up north. The AC was ice cold when off the highway, at slow speeds. But when I would get up towards 55 and above, i wasnt very cold at all. Any ideas?? Could it be low on charge?

Thanks
Bill

 

do you have a cutoff valve to the heater core? that might be the cause if you do not.

 

Not sure what you mean here???

 

Grunt...I think wolftan means a way to shut the flow of hot water to the heater core...Kwik is working on a solution to this problem...I don't think this is your problem though. How about taking the truck out and bring to operating temperature. Then stop and put the air conditioner on (with setting at lowest temp possible). Have someone bring the throttle up to 1500-1700 rpm and hold it (that would be your rpm at 55 mph roughly). You look under the hood to see if the air conditioner clutch is staying locked up as it should. It should stay engaged...if not the clutch assembly may be bad or the airgap between the clutch hub and the pulley needs to be adjusted. Be sure to do this test at air temps above 50F.

There are so many things to check out when the air conditioner goes south that it is hard to pinpoint the problem, but usually it is the clutch or freon supply. If the supply is low do not let anyone charge the system until a dye test is done to find the leak (some idiots will just charge the system w/o purging and dye leak checking). No sense adding freon to a system that is leaking...you'll be right back where you are now in short order.

Also check the temperature of the air coming out of the center register on the dash...it should be between 33 and 47 degrees F when the air temp is between 60-90 F...if it isn't it points to low freon. Just about everything else will require testing equipment that any good air conditioning shop will have. If you PM me I can send you some other diagnostic info.