I have a 99 with 90,000 miles. The A/C has always worked great, spring finally came around this year and it`s now blowing warm air. I checked the low side pressure with a cheapo Auto Zone gauge and it appears to have plenty of freon pressure. Where should I start?

 

lol at freon pressure...i think you mean refrigerant

 

Take it in and they will put dye in the system, find the leaks, repair.

 

I`m pretty sure it doesn`t have any leaks. The low side pressure was up where it should be.

 

Freon, refrigerant, 134a..... You knew what I meant.

 

to much or not enough refrigerant in there

 

There can`t be too much, nobody touched the system all winter.

 

AC's don't lose 134a all of a sudden. Actually, you should never really have to refill the freon or 134a if there was no leak. So, imo, there has to be a leak. Make sure that the dryer is working cause otherwise you will brake the compressor. Make sure to refill the 134a and hook it up to a vacuum overnight. Either way, if the compressor is running and is blowing hot air, i believe it means there's no 134a. Sooooo........have fun!!!!

 

You really need to get a reading for the high side as well to tell whats up with it.

 

my mechanic said the door that switches to blow cold or hot air was stuck covering the cold hole so it blows hot air.said i need an a/c audio amplyfier. idk if that helps...

 

I just had the same thing happen to me. I have a 98 Max and even though it was warmed up with the AC on 65 degrees and full blast it was pushing out hot air. Turns out my alternator wasn't connected properly which therefore caused my battery to run low on voltage which caused my AC compressor to stop working. I had just had the alternator swapped by a shop and they evidently didn't connect it completely. So my suggestion would be to see if your battery is in good working order. Good luck.

 

Plenty of pressure?? What was the reading and was that taken while the compressor was actually running?

Details people, we need details.

 

50psi on the low side, I have to check to make sure the compressor is turning.

 

When AC isn't working, it shouldn't blow warm/hot air, like you guys are saying, it should just not blow cold air (it shouldn't heat the incoming air). Is that what you mean? When the AC is on, it blows ambient temperature air? As if you had your 'economy' on?

 

The compressor is turning while the a/c is on, if I shut the a/c off the compressor clutch dis-engages. The compressor does not cycle on and off like it`s low on freon. I`m getting 55psi on the low side all the time, even with the engine off. I need to find a gauge set up to check the high side.

 

I support the air mix door theory. The FSM suggests visually confirming it's operation.

 

Can`t be that. The a/c lines coming through the firewall are both warm. Nothing cold is making it into the dash.

 

I would accuse your orifice tube of being clogged but one would think the pressures would be more off.

 

Becareful with the gauge. It may be the problem. You need to press it to get a good reading. that was my problem at first. Mine doesnt clip well so I get wrong pressure.


Low side : engine off pressure should be around 70 psi
engine on, should be around 32-35.

Mine was at 28-29 (on), and no cold air. its extremely sensitive.

I cant get 134a easly in my contry for ??? reason. So I put 12a. Put a can when the engine was running until 32-35 psi.
Some members told me that was the wrost idea, maybe...

I tried, and my a/c working perfectly since a year now.
no need to waste the 134a, its compatible.

This is the first thing to check. After, of curse, the compressor clutch.
After, if the air is warmer than the outside temperature, check the controler. it probally stock on heat. ( I had this problem with my dodge durango).

good luck

 

Check and make sure both cooling fans are operating when the A/C is turned on. That turned out to be my problem. Only 1 was operational. The result was "decent" cooling on the highway but little to no cold air around town.