99 5.2l AC issue

[sentrek]

Bought my kid a 99 5.2l a few weeks ago, the ac will blow cool (not cold) air for sometimes a minutes, sometimes 10 minutes, sometimes almost no time at all, and then will suddenly go full hot. Tried replacing the low pressure (ac clutch control?) switch but that didnt work. Any ideas what to try next?

 

[pacofortacos]

Well going full hot shouldn't happen unless you have a bad blend door or actuator.
When the AC is on, is the compressor clutch engaged?

 

[sentrek]

Honestly, I didn't check that before now, but I went out and tried it and the compressor clutch doesn't seem to be engaging at all now.

 

[chopperman1]

You say you changed the low pressure switch, did you evacuate it and recharge it?

 

[sentrek]

I haven't had a chance to do anything yet, just got it back from the shop having the water pump replaced and some other stuff. I didn't have the extra funds to have them deal with the AC. I am not an auto mechanic by any means so if the clutch isn't engaging what is evacuating it and recharging it going to do? Wouldnt that be waste if the compressor is bad?

 

[pacofortacos]

If there isn't any pressure in the system, the compressor won't engage.
Did you replace the low switch or did someone do it for you?
If it was you, did you hear any hissing or did any refrigerant come out when you removed the switch?
IF it did empty, did you at least recharge the system with refrigerant - evacuation and charge is best but most people don't have the evacuation system.

IF nothing came out, you probably have a leak, on that year the condenser in front of the radiator is a common place - look for a wet oily stain on it and all of the AC lines. Could be the evaporator but it's inside and not easily seen.

Quick check to tell if there's any refrigerant in the system, is to remove the high pressure port cap and do a quick push on the schrader valve - if it's empty nothing will come out, IF it has any refrigerant in it - it will come out when you push down on the valve, so use a small screwdriver and just a very quick push and release.

IF it's empty, you can try to charge it (you can buy the stuff in the auto parts) and see if you have a leak or if it will hold the charge. You might get lucky.

 

[sentrek]

I changed the switch, I did not hear anything and nothing came out which I thought was odd.
I have checked all the lines ect for a leak but I didn't find any evidence of a leak, but the engine bay on this thing is cleaner than my check, so most likely any evidence of a leak was washed away.
My son goes to school all day then works until about 10:30 and works weekend mornings but as soon as I get the chance I will do a quick check to see if its empty and if so try charging it. Thanks for the info!

 

[chopperman1]

When you changed the switch there was no pressure which means you have no refrigerant in the system. You can't just charge it, you need to evacuate it first. Need to get the air/moisture out of the system. You then need to find the leak and fix it or you'll just be back to square one.

 

[PaPitt]

I thought the pressure switch sat on top of a schrader valve. SO When you unscrewed it . The valve core kept it from letting your freon out.
Hiss unscrew it & put new one on & you only got one tiny Spit .
& you were back in business.
Am i wrong on that one.

 

[PaPitt]

Now if that blend door down on the floor is bad & has all your ac say going out the Defroster vents .. It sure will kill you inside.
My 2000 diesel bottom blend door is out .. But it can be turned up to top setting & it blows cold ''ALL'' the time . Then i freeze to death .
But that stinking Blend door cost over $200.00 now ..