My 1999 Ram 1500 AC compressor does not work. For a few weeks now the AC has worked spradically - blowing hot air when it doesn't blow cold. I have found no leaks in the vacuum lines. Now the compressor doesn't even cycle on. I can see that the clutch won't engage even though I've set the controls to max a/c and temperature **** to max cold. The fuses check ok.

Any ideas?

 

If you are low on refrigerant, your low pressure switch will not allow the compressor to turn on. If you don't want to find one of the many "free AC check" places, you can check it yourself by bypassing the low pressure switch. The switch is the two-wire plug on top of the accumulator. Remove the plug and place a jumper wire in both sides of the plug/harness. Then start the truck to see if the ac compressor starts when you turnthe ac on. If it does come on, you are low on refrigerant. Don't leave the jumper in, put it back together as it was.

 

That did it. After bypassing the relay, the compressor ran and I was able to refill the line with R134a & dye. I'll let it run for a bit and see if the dye leads me to a leak. thanks for your help.

 

The dye is carried in the oil so you have to let the a/c run alot to circulate it. The more it circulates, the better your chances of finding that leak. Might take days!
WC

 

It might help if you usea black light from the pet store; the ones you use to find urine in the carpet with (like the ones on CSI.) I thinkmost dyesadded to R134aarephosphorescent.It'll probably be easier to see than red andmight help you find it quicker. Justlook at night or in the garage w/ the lights off.

 

I noticed today that the clutch is turning on, and off imediately. Is that the same thing happening here?
I will try to jump the switch tomorrow when I get home.

 

thats whats happening to me, click sound, - like clutch on - then refrigerant pressure drops, click, pressure back to full, click, etc

ideas?

 

sounds like low refrigerant levels to me; clutch cycling on and off.

 

And a leaking evaporator.

 

what can i do to check those things? when I hook up the refrigerant refill, the gauge on that shows it to be full....was not full until I filled it. was empty as first, now its full, and not cold air