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.

 

[Pstyckiewicz]

Got around to testing some stuff. So my volt meter wasn’t work. I just jumped the wires on the dryer and the fans turned on under the wheel well. I did not see the clutch engaging on the a/c compressor. Also the fan under the wheel well was running while in heat mode and when fan on dash was off. It seems to run all the time. Not sure if that’s normal. Any suggestions for what to look at next? Get some gauges from harbor freight?