ac problem

hi guys can anyone help with this i have changed my compressor and dryer and all the o rings in the engine compartment vacuumed system and no more leaks. recharged the system and have good cold air most of the time.when im driving with air on all of a sudden it starts blowing not so cold air and humid,and then starts blowing cold again any thoughts

 

Any 'smoke' (fog) coming out the vents at these times?

 

Overcharged on refrigerant? I believe the compressor will cycle much more frequently if overcharged. Not positive on that though.

 

sounds like your expansion valve may be bad

 

Might want to look at all your HVAC linkage under your dash towards the floor. Almost sounds like the blend door opening and closing. These older pickups are known for that not working right. I have to manually move mine as the place where it connects to completely broke off. Manual blend door. ha only in a TACO

 

you need to first confirm if its the a/c or the heat that is the issue. turn off radio and listen for the compressor, you should be able to hear when it cycles on and off but I don't think it is because the air might not be "as cold" but it shouldn't feel warm and humid. you need to figure out if the a/c compressor is shutting off before going any farther.

to test if the heater is being activated, disconnect the heater hoses and connect them to each other using a copper coupling then go see how it acts to see if it is the heater coming on or if it is the a/c shutting off on you for a moment.

on our trucks the control is all electric so it could be opening the heater valve or the blend door on you or both. if the control is bad, that's not good and they are not cheap ($300+ I think new) and its best to replace with a used one from ebay or source one from a salvage yard or someone here with a 01-04 parts truck

 

thanks for the ideas, it is not overcharged it was completely vacumed out and the correct amount was added. i dont have any fogg coming out of the vents when it gets humid and i checked the compressor is shutting off when it starts to blow warm air havent checked to see if the freon level has dropped im thinking i may have a leak somewhere

 

The compressor will shut off if the freon pressure gets too high. There is a pressure switch. This protects the compressor from damage. Not sure if this is actually your problem, but just throwing this out as one reason the compressor will shut off temporarily.

 

can you tell me where the pressure switch is

 

Its pretty hard to get to high pressure switch. Its inside the evaporator box. How does your sight glass look on the drier? Is it clear or cloudy at 2500 rpm? What's your A/C pressures at 2500rpm and idle?

 

ya that doesnt look any fun,when i take off the low pressure cover i get a little hiss like its leaking i tightened it and tested it with spray no bubbles. when i put freon in should the can be upside down or right side up.

 

Even with that cap off, there shouldn't be any leaking out of that low pressure valve.

 

when i had it drained down i replace both high and low valves

 

Does the volume of air coming out of the vents decrease then increase after a short time, or remain constant and just get hot? What is your location and how humid is it?

 

But is it refrigerant leaking out? Sometimes just need a little lubricant, like pag oil to make sure that the valve gets a good seat against it's seal. Even weirder if you replaced those ac lines that have the valve on the line. If it's leaking, something is keeping it from sealing all the waym

 

If you can't get the valves to stop leaking. I believe the make a metal cap you can put on them that will help seal it. Or drain and replace them again.

 

just checked the sight glass is cloudy

 

Low on Freon then.

Do you have a set of gauges to check pressures?

 

Sounds like a slow leak somewhere, if you are positive that you charged system completely.