A/C Diagnostic help

[Pstyckiewicz]

I have an M1152A1 with the stock2 man A/C unit. I am just getting into the stage of fixing the A/C. The fan switch works on the dash. The vents blow air but it’s not blowing cold. I don’t hear the fans under the right rear wheel well turn on. I did hear them come on once before for a second. I’m not sure if I have a leak somewhere or if I have a bad low or high pressure sensor. Maybe a bad ground or wire issue.
I’m looking for somewhere to start. Maybe what wires to look at or connections to jiggle. Or O-rings to replace. I do have access to a vacuum to hook up to the system but I want to check the simple things first.

Any help is greatly appreciated!

 

[FlameRed]

First, let me state that I am a novice on the HMMWV, but there are certain things you can do.

Start by unplugging the connector at on top of the dryer - the low pressure switch. With the AC turned on, engine running, you should see 24V on one of the leads in the connectors with a VOM. If you don't have that - then you have electrical issues further down the chain. If you do have 24V, you can short the two lead swith a piece of wire for a couple of seconds and you should see the AC clutch engage and the compressor turn. If it does turn, that means you are low on charge - or empty of Freon. If it does not turn then you can look at something wrong with the clutch or compressor. If it does turn, then put a set of AC gauges on the high and low side and check your readings with the leads shorted again but I would bet your Freon level is low.

If the freon level is low, I usually whip out the freon sniffer and find the leak. If the thing is really low I might have to add a can of freon just to get something in the system to sniff out the leak.

Some auto part stores will loan out a sniffer and compressor gauge set for free with a deposit.

Hope this gets you started.

 

[Pstyckiewicz]

Awesome information!!! Thank you for taking the time to help me out!

 

[Pstyckiewicz]

The attached picture I believe is the air dryer wiring. There appears to be three wires from the relay. I’ll test it to see if I get 24v.

 

[Mogman]

Invest in a cheap set of gauges!! HF has them.