A/C Compressor questionable?

Lately on pretty cold mornings, my a/c compressor won't kick on when turned to defrost (or any other setting where it should come on). The blend door opens to the defrost vents, but the compressor doesn't kick on. However, later in the day (after it warms up a bit) the compressor cycles just fine. Any ideas? Is the compressor to blame (some how) or could the problem be lying elsewhere?

depends how cold were talkin about, when the internal pressure drops below something like 20 psi on the low side the low press switch will prevent compressor operation. cold weather equals lower pressures so its probably normal and can prevent compressor damage also

Currently we're talking about mid-20's. I just don't remember this happening in past winters.

Your probably getting low on refrigerant. You could check it out right with gages or take a small chance and just throw another can into the system. Over time, even a good system slowly loses a little bit of refrigerent. Was the air good and cold last summer?

Hi,
I had problems with my compressor not kicking in last summer. After having several headaches over it i got an air con guy come and have a look.
After testing everything, he said that the gap between the comprssor and clutch was just slightly too big for the magnet to pull the clutch in to engage. All he done was remove a TINY shim, and hey presto, its worked well ever since. Maybe the cold is effecting your gap in some way, and then when things warm up a little, the gap is closed enough so that it can engage.
only a thought, but perhaps worth trying with the cheap and easy stuff first.

winterbeater said:

Your probably getting low on refrigerant. You could check it out right with gages or take a small chance and just throw another can into the system. Over time, even a good system slowly loses a little bit of refrigerent. Was the air good and cold last summer?

Click to expand...

Air was good over the summer. Ridded the system of moisture and charged it around June.

dunbad said:

Hi,
I had problems with my compressor not kicking in last summer. After having several headaches over it i got an air con guy come and have a look.
After testing everything, he said that the gap between the comprssor and clutch was just slightly too big for the magnet to pull the clutch in to engage. All he done was remove a TINY shim, and hey presto, its worked well ever since. Maybe the cold is effecting your gap in some way, and then when things warm up a little, the gap is closed enough so that it can engage.
only a thought, but perhaps worth trying with the cheap and easy stuff first.

Click to expand...

Any pics of this? I haven't taken a look, but this sounds like a likely possibility.

Hi,
I havent got pictures of it sorry, but its easy to see. The clutch is obviously the metal plate on the very front of the compressor that spins when the a/c kicks in.

There are usually a number of tiny shims (washers) that separate the clutch from the compressor. The gap in between is called "air gap". Try doing a search and you will see more.
I understand that on some cars there are many shims, on mine, there was just one shim.
My aircon kicked in fine in the summer, but then died after about 10 or 20 minutes or something like that. My aircon guy said that the difference in temprature was effecting this air gap as metals heat or cool, expand or shrink etc.
The only way i could get the a/c to work again was to leave the car off for several hours.

He said that Tapping the clutch towards the compressor with the motor running:skull1: !!! was a good indication to see wether the air gap was too big as the clutch usually would kick in once its tapped. This is very dangerous and i wouldnt try it. Its just what this guy said.

He tried this on my car but it still wouldnt kick in. Apparently the measurement between clutch and compressor (air gap) was good, but he knew somehow that this was the problem as he had tested everything. He removed just one tiny shim that was no thicker than a piece of paper and its worked well ever since.

let us know how you get on

I assumed that you now where the compressor and clutch are?? If not i shall take a picture.
I know that the gap can be measured using a tool. My gap at the time was within these measurements but was still the problem. Its something very roughly like credit card thickness to christmas card thickness!!
but i know that the exact measurments are on this site. It took the guy no more than a few minutes to take this TINY shim out. He just removed the clutch plate, took out shim, then put the clutch plate back.