The compressor doesn't engage after vacuum pump

[kamhoe]

Hi there,


I need some advice to charge my A/C.


My compressor was running before I did a vacuum pump to check for a leak.


When I tried to charge a can of r134a, the compressor doesn't engage & the gauge remain 0 pressure on both.


How do I get the compressor to kick in?

[andrewwynn]

Spec is 430-450g of R134a. Did it take the full can 340 g i would expect you'd get some pressure from the first can.

[kamhoe]

The compressor doesn't engage & doesn't suck in any freon. The pressure remain 0.

[andrewwynn]

Freon can has about 50 psi. Sounds like you didn't have the valve open to let in the gas or you have a very bad leak. Was the vacuum able to hold for 30 minutes and did you hook up the vacuum through the fill port on the gauge set?

[Masospaghetti]

^ this is correct. There is a low pressure cutoff so the compressor won't run on a dry system and self destruct. The lubricant is carried by the refrigerant so it protects itself by cutting off. To get things started you need to build enough pressure from the first can. I've never had an issue doing this. If it's cold outside you can put the can in a warm bath of water to help it along.

[kamhoe]

My vacuum was holding ~-25 for over an hour before I decided to start the charge. The ambient temperature is 55F & I was wonder if that cause the compressor doesn't engage.


Maybe I will try to warm the can in water bath tomorrow.


Thanks for the suggestion.


Is there a way to manually engage the compressor? BTW, mine is 2005 X5 4.4i.

[andrewwynn]

When a compressor won't engage, i usually use a 12v drill battery to hotwire but you need pressure in the circuit first.

[kamhoe]

Finally the compressor engaged by soaping another new can in warm water bath.

Thanks all!

[X5chemist]

Did you swap out the pressure switch while it was empty? Or change the dryer? I charged mine to the lower end pressure scale of R134. Even on 100F days, it will cool down to 42F.

When it leaks out and you can't find the leak, the valve cores are likely the source. I replace valve cores if I empty an A/C system.

[kamhoe]

Originally Posted by X5chemist

Did you swap out the pressure switch while it was empty? Or change the dryer? I charged mine to the lower end pressure scale of R134. Even on 100F days, it will cool down to 42F.

When it leaks out and you can't find the leak, the valve cores are likely the source. I replace valve cores if I empty an A/C system.

I added dye last summer but I couldn't find any leak from the engine bay area. It could be from the evaporator side.


The compressor was engaged before I did the vacuum leak check. I didn't replace any part. I think the compressor couldn't engage due to the r134a can pressure was too low.


FYI, stealership wanted to charge me $598 just to do A/C diagnosis. Indy charges $198 & recommended me to recharge A/C yearly instead of replacing evaporator that costs $3500.