A/C worked yesterday, nothing today


Active LVC Member
Nov 26, 2014
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2005 LS V8. 100K miles. AC has been fine up until today. Now, no click and the compressor is not engaging.

I did check the AC fuse. Then I moved on to the relay and tested the voltages at the relay pins. The 2 tested for 13.98 volts, so that part is good. I swapped the relay out and it did not engage the pulley.

Any suggestions for the next step would be appreciated.
Check your refrigerant level. (Clutch will not engage if too low)
Check for power at the clutch connector (if refrigerant is not low, at least 50 PSI)
Check evaporator temperature sensor if no power at clutch.
Check clutch coil resistance if there is power. If that is good, check clutch air gap.
Thanks Joegr. This one might be beyond me, because I do not have any gauges to test with. I might try a charge of refrigerant and see if that brings the pressures back up.

I can't even see the compressor, under all those covers. It's too hot to mess with it today.
And I am getting ready to move cross country, so not a lot of time to spend on this.
...I might try a charge of refrigerant and see if that brings the pressures back up...

Please don't. Too much refrigerant is worse than too little. You can't correctly charge the system without high and low side gauges, pressure charts, and using the correct procedure.
Ok, Joe, I will pass on the refill. If it's the evaporator temperature sensor, if can unplug it and it's bad, the compressor will kick on? Under the dash on the driver's side?
The 2 white plugs I see under the dash do not appear to have anything attached to them. Am I looking in the right spot?

Look a little lower too (may have to pull the carpet back some). I can't tell from the picture, are you positive that nothing is plugged into the top side of the that connector? The bottom side that is showing is correct (a void with nothing plugged in).
I will take a better look. But here are the 2 plugs from a closer look:

I still can't tell if there is a cable coming out the other end. I think there is. There should be.
Well, we did unplug that sensor and the compressor did not engage. Going to have a shop check the pressures and the system. I need AC, lol
I had to fix the AC on my 04 just this weekend. It had rapidly leaked down to where it was barely working. The leak was obvious once I took the splash shield off under the compressor. It was the low side port valve. I replaced the high side port valve while I was at it. So far, so good.
I hope mine just blew out a valve, because it was a sudden loss of the system. It blew cold for years and just stopped overnight.
I hope mine just blew out a valve, because it was a sudden loss of the system. It blew cold for years and just stopped overnight.

A common leak point is the 0-ring for the scroll control valve on the back of the compressor. Unfortunately, if you don't notice it you will lose most of your compressor oil before you lose the refrigerant.
Well, we checked the system today and it is basically out of refrigerant. My friend has all the gauges to vacuum the system and we will pull it down tomorrow and see where the leak is. I had the cover off before and didn't see any signs of oil leaking, so I am hoping it is the low/high side port valves. Are the parts available at the local parts store?
Charged the system today and it is back working. He went over all the fittings looking for any leaks using his fluids and couldn't find any.
It's working again, will see how long it lasts.
Looks like I'm in the same situation, an A/C issue. Put my gauges on (estate sale) and got 60psi (low) on both sides @80F. Compressor does engage, just no pressure changes, so that doesn't look good. Normally I don't mess with A/C.

Loaded to 75psi statically, where it should be. Wasn't expecting a change, still even low and high, low drops with an increase in rpm.

I'm going to guess compressor.
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The usual compressor failure is for it to work at high RPMs and not at idle. The failure in that case is the scroll control valve.
You lost a lot of refrigerant. You need to identify the leak first. If it is the compressor, then your plan is good. If it's not, then you have more repairs to make.

You need to replace the receiver/dryer too.
Only took a few oz to bring the pressure up. In the fall the wife said she thought the AC only worked at speed, but it also had an electric fan failure at the same time which is what I thought the AC situation was also due to.

Compressor and receiver ordered earlier, may pickup a condenser too.

I can throw some dye in beforehand to hunt down the leak if it will do it at static.

I'm thinking back to 8-10 years ago when I had the system evac'd and refilled when I checked the timing setup. I gave the neighbor (used car flipper) an 8oz can of Motorcraft PAG in case he needed oil and it was empty enough that I threw it away. Now I'm wondering if he overloaded it. So much for bartering work.
Where ever it is leaking, should be pretty dirty. You shouldn't need dye to find the leak. The factory charge had yellow/green UV dye in it.
I just don't know if my guy flipped back in my old charge from the recovery. I'll hunt for dirt tomorrow.

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