AC Repair help needed

I have repaired many car ac systems but this has me stumped. My compressor is working but I am getting some strange pressures, 35 low and 40 high with the comp running. I evacuated the freon and want to recharge after vac. My compressor is still running with no charge in the lines, how is this possible? Is the low pressure switch not working? Thanks for the help.

 

Your sure the magnetic clutch is engaged ?? The clutch is just free wheeling ?

I need to ask the simple questions of anyone.



Test for voltage at the compressor connection.

Strange things do happen the low pressure switch has failed in the closed position.

When was the last time the AC did work?? The compressor has completely failed and while it spins no pressure is being built .

The vacuum pulled enough refrigerant in to read the pressure you do have close enough to being equal.

 

The clutch is engaging.
ac worked a couple of days ago.
Sucking now and will get some freon in soon.
Thanks

I am trying to determine if the compressor is not working, it is not making any noise, in the past I have had bad compressors and the either lock up or start screaming. This one sounds fine, but you are right, it might not be pumping anything.
thanks again

 

Update
pulled vac and put in some freon, clutch engaged and compressor is running.
100 psi on both low and high side. no change after running for 5 min.
Does this confirm a bad compressor?
Expansion valve?

If I replace compressor should I also do expansion valve as well as condensor dryer?

Some are recommending replacing all components due to contamination, is this necessary? The dryer under the dash would be fun.

mucho thanks

 

If the clutch is turning and both pressures are equalized you have a bad compressor...also replace the receiver dryer

 

Sounds like a bad compressor, if there's metal in the system your gona need to also do the condenser, expansion valve & screen, and flush the evaporator and lines thoroughly.

 

Update
I let the car run for another 15 min and the high pressure started to rise slowly. I put in the specified amount of freon but it took a long time. It took a long time for the low side pressure to go down after adding freon, longer than other cars I have worked on. Low is now 40 high 195, blowing cold. I still do not think everything is OK, I think maybe the expansion valve was stuck and suddenly started working again? I will run it until it happens again. I think this confirms that the compressor is working....for now. Thanks for all your help.

 

Dryer under the dash?

Pray tell what started this adventure? Seems like you have a leak that should always be the first step find and repair.

What did the manifold gauges read when you hooked up the vacuum pump?

The fact the clutch pulled in on a empty system something is very wrong someplace.

 

Yes, dryer under dash.
It started 32 years ago with the birth of my daughter. When her car breaks, it becomes mine. She delivered it to me no AC working. I found a blown compressor fuse. Replaced fuse and compressor started engaging. No cold air and wacky gauge readings 35 psi both sides running sometimes high on the low side and lower on the high side. After screwing around a while I had some freon leak out through a loose connection on gauges so decided to evacuate and start from scratch. Yes I did run the compressor with no freon in. Vacuum was fine and held for 30 min before I refilled it. When refilling the compressor kicked on at 35 lbs and as said before the strange slow building of pressure when refilling freon.

I agree with you that something is still wrong, I put some dye in it to see if it has a leak. Expansion valve or condensor restriction. It is 105 here and humid today, happy to have it working for a little bit. thank you for your interest as I am perplexed.

 

A/C is some of the easiest and hardest repairs you'll ever do. They can do some of the most weird things pressure wise you can ever come up with in your mind. Intermittent issues are a PITA to figure out when it [of course] always works fine when you start to work on it.