AC blowing hot air, after system vacuumed & it worked for 3 days.

Here’s my bunk switch plug. It’s melted. Just bought it ( short harness) couple years ago. I’m not buying another. Got new ends for the wires, attach them one at a time. Did that on my last one. It must be caused by the switch terminals getting loose. Cheap switches. I have mine running constantly now, attached burned wire to burned plug terminal with alligator clip. Doesn’t get hot at all.

 

It blows cool or cold first thing in the morning when under hood temps are cool from being off all night but once it gets hot under there, warm air? That would point to somebody screwed something up at the shop. Either overcharged it with freon or somehow caused a slow leak and now 3 days later enough has leaked out for it not to work right. Any other clues? Compressor short-cycling off and on? Green oil puking out of the pressure relief valve into the engine bay? (usually near the compressor to keep it from blowing up if overcharged and PSI is too high). Sometimes they damage the schrader valves hooking up the machine causing a leak in the system.

 

I'am not trying start a argument with you actualy from a Diagnostic ponit of view you are probably correct as being lown on refrigerant
But I wish you wouldn't be so quick to blame shops for poor workman ship
I've worke on HVAC issues for close to 20 years what you fail to realize is no one brings in a truck with perfectly good working A/C
Talking from experience you can fix the problem at hand .. and sometimes once it working properly at the correct pressures and it its used the other weak points tend to show themselves .. maybe a new leak develops .. maybe the correct pressures cause the expansion valve to get suck .. and maybe the inertial problem wasa leaky condenser that was repaired and everything was in correct working order and 5 days later its not working and come to find out now the clutch is slipping on the compressor or the Evaporator suddenly started leaking because it was on the Is verge of leaking before.. you just never know .. but everybody is quick to point the finger at the shop that just worked on.it Previously ..
Thats really why I don't like working on other peoples A/C cause you seem to be married to it once you touch it
If you have worked on as many as I have over the years and seen some of the things I have .. you might not be so quick to place the blame on a shop's workman's ship

 

I stated already they are fussy systems to troubleshoot when they quit working right. It might have been something related to getting recharged that wasn't anything the shop did wrong. On an older vehicle sometimes the only right way to do it is replace everything at once with all new parts. Obviously that gets expensive. He should take it back though because something is up if it quit working right 3 days later.

 

Ok, description of symptoms is changing. You said it will quit running down the road. Now only when idling. If only when idling, usually it’s because either the fan isn’t operating, or the front of the radiator (cooling fins) is blocked by debris.

 

That would point to a fan issue if it blows cool when under way (30-40 mph at least), but goes warm in stop and go and idling. I took the fan and clutch completely off my 7.3 Ford for awhile once and saw this to be the case. The condenser needs airflow past it to cool the hot gas coming out of the compressor or the system wont work right. I don't really understand the physics behind it I just know from experience that's what happens.