AC Compresor not coming on

First post. 98 Intrigue, 3800, 95K miles, white paint :iceslolan.

My A/C doesn't work. When pressing the switch (digital climate control), the LED on the A/c button blinks 4-5 times, then goes out. Holding it, etc. doesn't work.

Here are the diagnostic steps I've taken so far:

- Belt is fine and pulley is turning, compressor doesn't turn. This suggests that the clutch isn't engaging.

- Refrigerant pressure was checked by a friend of family who is a home HVAC technician. I will put a gauge on it to verify pressure, though.

- Under hood fuse box:

Checked fuse 23, good.

Checked relay 15 (a/c clutch), coil is good. Swapped relays with position 16 (horn), as they are the same relay. Horn works with both.

Checked diode, 10:1 ratio.

- Pulled wiring harness from a/c clutch, no voltage reading at the terminal when attempting to switch a/c on. It should be 12V (hot) and 0.5V (ground), right?

Everything tells me that something is wrong in the wiring between the switch and the clutch. How do I pinpoint this further?

Also, is there a way to put voltage directly to the a/c clutch to verify its proper operation. Should I ground it if I do?

Thanks for any and all diagnostic tips.

its probably just low on refrigerant....mine did not work until i added a can of r12a to the low side line, and now its fine. If not do what i did in my truck and follow scotty kilmers advice...this guy is genius!

http://www.youtube.com/watch?v=ah4OEeCu1KE

The light flashing means you have a HVAC code set- that is why the a/c won't come on-- the computer won't allow it- so quit looking at wires- you need a HVAC capable code scanner to read the code- could be anything from a temp sensor- (does your outside temp display work and show proper temp?) to a sunload sensor- to a low charge algorithm - you can remove power from it to temporarily reset it- and see if compressor comes on-- by unhooking battery for 10 seconds..

Most likely you are low on charge- and your car is saving you from burning up your compressor- until the leak is fixed and it is re-charged

The light flashing means you have a HVAC code set- that is why the a/c won't come on-- the computer won't allow it- so quit looking at wires- you need a HVAC capable code scanner to read the code- could be anything from a temp sensor- (does your outside temp display work and show proper temp?) to a sunload sensor- to a low charge algorithm - you can remove power from it to temporarily reset it- and see if compressor comes on-- by unhooking battery for 10 seconds..

Most likely you are low on charge- and your car is saving you from burning up your compressor- until the leak is fixed and it is re-charged



Thanks very much for this starting advice. I went outside this evening to check the pressure, the first thing I intended to do. I started the engine, turned on the A/C at the switch - the light did not flash like last night but stayed on - and I looked under the hood and the compressor was turning, unfortunately it was only blowing hot air.

I meant to mention in last night's post - the external temp sensor is reading accurately.

The refrigerant pressure, read at the low pressure port, is 52 psi. The "green range" on my gauge is 28-55 psi, so my charge is at the high end of the acceptable range. I checked with the family friend who checked/topped off last week when air first started blowing hot. He said that the pressure then was ~38 psi, and he added some stop leak R134a, just in case, and charged it to 50 psi. Since my reading was 52 psi (acceptable differences in gauges, I would guess), I suspect I don't have a leak.

After I shut it down, I unhooked the battery for at least 15 minutes to reset the computer, and restarted the engine and turned on the air. Again, the compressor was running, the LED was on, the setting was lower than the outside temp, so all indications are that it should have been blowing cold air. I gave it several minutes, but the fan always blew hot air.

I'll keep seeking the problem, and further advice is much appreciated.

52 psi suction is why you are not cooling- that number would be fine if it is 110+ degreesf out-- what is your high side?-- have your a/c buddy hook up his gage set and give us that reading- if the high side is 90 or below- then your pump is bad-- what engine in your car? if it is the 3,5L you have a V-7 compressor, if it is the 3800 you have a V-5 compressor- in either case you need the high side to determine if pump is ok..

feel the steel A/C lines under the hood, they come right off the compressor so if they aren't cold then your compressor is not pumping.

Thanks again. It is a 3800, so V-5. The refrigerant line on either side of the low pressure port is not cold, but it's not hot to the touch either. The ambient temp was ~90F last night, certainly not 110 though.

I'll have high side pressure checked and hope for the best.

I see I can get a rebuilt V5 for ~$200. How difficult is that replacement job (if compressor turns out to be the problem).

Update: Compressor was not pumping although it was running. Put a new compressor on, air is COLD!!!!!!!! Thanks for the advice.