Compressor Clutch not engaging.

[Matthew23451]

I drive a 2009 Ram 1500 5.7. I was running low on freon for a while and I just held of until spring to get some freon. During that time, my freon got so low that my compressor clutch quit engaging (apparently some safety measure). Now I have freon but i cannot get the A/C to cycle it through so the clutch will engage. Ive tried bypassing the clutch relay with a wire, however it will still not engage. I can't find any fuses or other relays in the fuse box. I was wondering if there is some kind of reset i need to perform in the trucks computer or something.

 

[PaulTGarrett]

First off, there is a low pressure safety switch that protects the compressor from low freon. If you don't already have enough freon charging the system, that safety switch will remain open and your compressor will not kick in. What I am going to describe will get your compressor running but be aware that there are moving parts under the hood!

So... Get a piece of wire a few feet long. WITH THE ENGINE OFF, wrap one end of the wire around the positive post on your battery. Find the wire coming out from behind the compressor clutch, then find the wire connector. Disconnect that wire connector. Then put the end of the wire connected to the battery into the clutch side of the connector. You should see the front of the clutch pull in and hear a good healthy click. Pull the wire out of the connector and the clutch should relax and you should hear somewhat of a tick. Repeat it a couple of times to make sure. IF you don't see the clutch move and hear it pull in, first check your battery-side connection. When you get the compressor clicking, let's get things moving.

Start your engine, set the AC to MAX, temp to polar bear. Go back to the wire from the battery, poke it into the clutch connector. It will pull in and the compressor should spin. Hook up your freon kit and put some freon in the lines. Follow the kit's instructions until the system is starting to look right.

Now let's see if the system is working... Turn off the engine. Remove the wire from the battery and the clutch connector. Plug the clutch connector back into it's original wire. Start the engine back up. If the compressor pulls in, everything is working just like it is supposed to and you can continue adding freon until the system is correctly charged.

If the compressor still doesn't pull in on it's own, go back to step one and add more freon. If you end up with a full charge and the compressor still won't work on it's own, you have some other electrical problem that will require more diagnosis. But you first need to get enough of a charge that the AC system's safety switches will allow the electrical part of the system to operate.

 

[Cool_Hand_Luke]

I Have a similar problem with my 2002 Ram 1500 4.7
The thing is that my AC clutch will always engage when engine is cold but will shut off about 15-20 after. I can turn it back on by either turning the engine off and let it cool off or turn off the a/c for same amount of time. I can then start AC again for small amount of time. I hooked up the guages and while idling it shows about 35 PSI on low and about 180 PSI on hi side.
According my repair manual the pressure should be 30-40 and 250. My reading is while idling and i think the correct chrysler reading should be at 2000 rpm which would be even lower and that would mean i'm low in refrigerant. Is this correct? Or should I be looking at pressure switch (tranducer).
Btw, when AC works, its ice cold.
Any info would be greatly appreciated.

 

[Tach_tech]

If the refrigerant is low there’s a leak, you should fix the leak.
Usually I would strongly advise against adding refrigerant yourself, as I’ve seen a lot of systems ruined by people trying to do it themselves.

That being said if you’re going to do it yourself, do not get anything with a stop leak. The stop leak crap in it will likely clog the system and turn a small repair into a big expensive one.

As for getting the compressor running, just remove the connector for the low pressure switch and install a jumper between the two pins in the connector. This will trick the system into thinking there is refrigerant in the system. It’s a lot easier to do that then hot wiring the compressor.

Do that a few times until there is enough that it will cycle itself.

 

[bpolly2004]

I am having a similar issue. 2009 ram 1500 5.7. I Replaced blend door actuator in back of hvac box by the firewall. I had the ac evacuated before and refilled by the same shop about 2 weeks apart. After the shop refilled it yesterday I still didn't have ac. The air blows but just hot air. The shop told me to tap on the clutch with a mallet. I did and the clutch moves when I move it by hand. I checked the ohm reading between contacts of the ac compressor. It was 11.5 ohms. I tried to bypass and ran a wire from battery to the contact. I got nothing. No click no movement or anything. I am full of freon and dont know where to go from here. Please help.