Title says it, AC blows hot. I have check the fuses inside and out and they seem to be good. I swapped relays with the horn relay and horn still works so relay seems to be alright. I do not hear the compressor engaging so that is one of my next stops.
Does anyone know if the compressor will engage when the truck is off?


Also my stereo, which was also not working when I got my truck back, had a blown fuse. I figure that some how some way these are related to each other. What do you say PT?

 

Should. Or, stand and watch it with the motor running. while your assistant turns the AC on. What are the pressures?

No. Not related.

My 1st guess would be, low/no refrigerant. 2nd guess would be the temp blend door actuator.
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Thanks RB0. I will have to take it to my girl's dad, he has the gauge set to check for pressures.

It looked to me yesterday like the compressor was not spinning at all when I had my assistant run the AC with engine on. I would be surprised to have low or no refrigerant since it blew ice cold when I last drove it. I'll take it over there right now or tomorrow and see what the pressures are

 

On the pressures, you should see the same on both sides when it's not spinning, which, no matter how much or how little refrigerant is in there, should be maybe 10 - 20 psi higher than ambient temp in °F. Then when it runs, if the comp ever kicks in, if it's low, the low side will drop INSTANTLY to like 15 or 20 on the gauge, and the cutoff switch will kill the comp.

If the comp is running, the suction line should be cold to the touch. Sweating, and maybe iced, depending on ambient conditions. If it's doing all that, then probably the blend actuator.

 

It's 28 degrees with the windchill of 23 degrees here and you guys are talking about air conditioning

 

you could have a stuck blender door as well. I had issues with my 05. ac would blow cold and the next time I got in it blew hot. if I moved the control from hot to cold a bunch of times it would blow cold again. I eventually ended up replacing the blender motor and it solved the problem.

 

It was 90 today
I would be surprised as this has never happened to me but it could be coincidence. We'll see sometime next week hopefully

 

My 2001 had a small leak in the evaporator under the dash, so it would work great, then when it got low enough to trigger the low pressure switch, nothing. On my wife's Civic, the compressor clutch went bad, so again, worked great one day then nothing. AC if very easy to work on with a gauge set and knowledge of how the system works in the vehicle you are working on.

If you plan on keeping your truck for a while and being your truck is a 99, if you have to open up the system to swap something significant, like the compressor, I would consider changing as many seals as you can easily get too and flushing the system. When I swapped my compressor for the newer style compressor (required for the turbo setup), I flushed the system, replaced all the seals, used a new orifice valve, and even replaced the rubber hoses (using all GM stuff) because I was already in the system. Before doing all that I had to touch the AC system at least once a year, which made me accumulate all the tools. For the last few years it has been rock solid and blows super cold. That 20 to 25 year mark seems to be when AC systems need to be completely rebuilt to continue to be leak and issue free.

 

To add to pknowles post and probably no help to the OP, if your compressor fails internally and puts any metal flakes at all into the system, you must replace the condenser.

 

Almost 49 yrs as an AC and Refrig guy and I only have basic knowledge of vehicle AC's. I help techs all over the country on a weekly basis diagnose problems over the phone on residential and commercial and am a total dumbass on vehicles. Lol at me huh? Wish I could help Evan. You could check continuity on the low pressure switch if no gauges. If it's open she ain't gonna try.