why does a/c go hot at idle (when stopped)? blows acceptable (but not great) when driving but at stoplights/ parked goes imidiatly to blowing warm.

 

compressor slows down at idle. No air moving across the condenser. check fan or fan clutch.

 

Running dual progressively controlled electric fans, so it has plenty of air flow through condenser. Now my Blazer is doing the same thing.

 

Is it time to recharge the system?

 

What kind of refrigerant are you using? My experience is that a replacement like R134a is not as efficient so it won't cool as well when there is not enough air flowing over it and the compressor is not spinning that fast.

 

Probably charge is getting low. Have you had it charged recently?

 

From my past I learned it to be a loose belt.. Stone

 

Probably

The Blazer is the easiest to diagnosis. Its 2001 (12 years old), 150,000 miles, factory sealed system (r134a). The manual fan clutch gave out, it overheated, and cracked the radiator. Had dexcool, that had solidified. I replaced everything that the coolant ran through exept the block and heater core (I have a new heater core, just have to find the time). Radiator, all hoses, pump, thermostat. Serp belt was cracked so I replaced it as well. As soon as I started it with the new belt the tensioner grenaded. So it got a new tensioner.

When all the new parts went on I removed the manual fan and went to a dual electric fan set up (something like 3,000 cfm). Put some fancy flex-a-lite progressive fan control on with brings the fans on at about 50% power and increases to 100% as needed. The controller is wired with an A/C request which automatically turns the fans on with A/C.

The A/C system was starting to feel hotter at the vents over time so I checked the temp and it was 60*. After the E-fans were added vent temp dropped to 55*.

Over the last week the vent temp will be cold but at idle will go to the same temp as the outside air is at.

I imagine its time for new o rings, charge, and orfice tube. I guess the real question is should I replace the drier and compressor while I am at it? I didn't know if the system going hot at idle meant it was just time for a service, or if a part was starting to fail.

 

The difference is that at a stop light, you're relying 100% on the radiator fans to cool the condenser. At 40 mph or less, you've got radiator fans and up to 40 mph of wind blowing into the condenser. Above that, the fans shut off and the wind alone cools the condenser.

I'm surprised you replaced all that stuff for your Blazer. We have a 2002 Blazer and that single gigantic fan does a great job keeping the vehicle at 195° coolant temps, even in traffic jams, 100° weather etc. Today it was 98° and it got down to 33° duct temps with the fan on #3. (It did take a while to get there).......Yesterday it was a 107° and it was noticeably warmer coming out the ducts. In fact, yesterday was the first time I've ever heard the radiator fan switch to it's higher noisier speed while driving (aside from the usual 20 seconds or so at startup)

Still running the stock radiator and air conditioning in the Blazer with the one exception of running Cool Top instead of R-134a.

What kind of weather are you getting in Kansas right now?

 

Weather here is amazing 86* all week in July.

I went to e fans for fuel mileage. I drive about 50 miles a day. Im at 21.5, with 150,000 miles on plugs and wires.

Heater core went in on the fourth, 12 hours.

 

With 150K showing, my guess is the compressor is getting worn out. But, that may not be the case every time, my DD 95 Roadmaster wagon has 215K on it and the R134 blows cold as heck even @ idle so who knows. That LT1 will probably live forever! Lol