1999 AC not working
 

Hi

The AC on my sons 300M stopped working. No fault codes from the ATC, the compressor clutch won't engage, and when we hooked up a bottle to charge, the pressure was at the max of the gage (bought an 18 oz can of arctic freeze 134a refrig w/ an attached gage and low side delivery line), 150 psi.

Since the compressor did not engage, my understanding is i might not be reading true system pressure.

There is a 2 wire connector at the top of the compressor. I started the engine and turned on AC and checked the voltage - none.

A friend w/ experience on LHS models said that it might be the relay or pressure sensing switch, but that it cannot be tested w/o the proper equipment.

Also my son said there was a funny smell when he noticed ac was not working (not sure if this is related at all, does 134a smell funny?)

My son swapped the clutch relay module out (wipers have same p/n so he figured he could swap them, wipers worked w/ either module).

Is there anything else I can do before going for expensive repairs at a mechanic or dealer?

Should I try to charge it? I was told if the pressure was above the max for my ambient temp which wanted to be <55 psi, that I should not attempt to charge it, but I think that assumed the compressor was running right?

Thanks
nayborbob

how about check the ac clutch fuse if its blown more then likely the compressor is fried.

1999 AC not working
 

I checked the relay, its fine.

update
 

Well we jumped the relay to the compressor, it started up, so we began filling w/ 134a. emptied an 18oz bottle. AC was making cold air in the car but when we removed the jumper the compressor would not start. So we surmised maybe it was still too low, as it was only reading 35 psi and we were looking for 45-55. So we bought another can and started putting that in. I didn't think we hit system pressure yet, as we were not filling long, but maybe it comes up fast at the end? Anyway we got discharge from the overpressure relief port. I think we put in about 22 oz (25 is what I believe the system should hold). Upon un-jumping it again, the compressor still will not fire up on its own. We did try to run the ATC diagnostic while it was running on jumper - no codes.

I am thinking there are a couple conclusions.... first there must be a leak if we had to put so much in to get to pressure. 2nd, something is still not right in the system because the compressor is being disabled, I am assuming by the computer. So I am guessing that might be a bad sensor or something.

I think we will need to take it to someone w/ a DRB, unless anyone out there has any other suggestions.

Thanks

i never said relay I said FUSE check the ac clutch FUSE under the hood

fuse
 

Sorry, I looked at all the fuses in the (PDC?). Did not see one for the compressor... I will try to figure out where it is. I thought you meant the relay since I could not find a fuse...

use your owners manual

OK I found the fuse, it was loc 21 in the interior fuse block. That fuse is also fine.

that is not the fuse I was talking about fuse 8 30 amp under the hood.