A/C trouble shooting

[jvsutton]

I have an intermittent problem with my compressor. It will work sometimes for days, sometimes for only about 15 minutes then it'll stop cycling. Seems to be totally random and has nothing to do with outside temps. Sometimes after I kill the truck and then start it again it'll work for a while, but always stops and blows ambient temp air.

I tried disconnecting the low pressure switch and jumping it. When I jumped it I noticed the engine speed raised, but the clutch didn't engage. So I checked the wiring at the connector to see if it was getting 12 volts, it would periodically show some voltage, and sometimes be nothing??? I know you aren't supposed to throw parts at problems, but I went ahead and bought a new a/c clutch relay for the underhood fuse box just incase that was the problem and wasn't supplying constant power to the low pressure switch. Well it wasn't because it's still acting up. I have looked for a wiring diagram to see how the switches are wired and where they get their power from, but can't find anything.

When the compressor is running the air is plenty cold and my pressures at 83^ outside show on the gauges as steady 40 on the low side, 175 on the high side. So my pressures seems fine to me, I just can't figure out why the stupid clutch won't stay engaged.

Should the connectors to the pressure switches, both low and high sides have 12 volts in?

Sorry for the long winded story, but I hope some of you have some ideas.

The truck is a 99 1500 V6 2WD.

 

[dudeman2009]

I'm going off the 00-01 diagrams, it should be the same, but i'm not 100% on that.

If the engine RPM increases when A/C is desired but the clutch doesn't engage, that rules out all the interior control circuitry. That leave the connection from battery positive to the compressor relay, PCM to the compressor relay, relay to compressor clutch and clutch to ground.

Since all the battery connections are in the Fuse box, we can ignore those for now. Check the resistance of the compressor clutch coil, try moving and striking the clutch while testing. When its acting up, check for continuity to ground on pin 85 of the compressor relay, you should have continuity.

 

[Shadow_Death]

I'm going off the 00-01 diagrams, it should be the same, but i'm not 100% on that.

If the engine RPM increases when A/C is desired but the clutch doesn't engage, that rules out all the interior control circuitry. That leave the connection from battery positive to the compressor relay, PCM to the compressor relay, relay to compressor clutch and clutch to ground.

Since all the battery connections are in the Fuse box, we can ignore those for now. Check the resistance of the compressor clutch coil, try moving and striking the clutch while testing. When its acting up, check for continuity to ground on pin 85 of the compressor relay, you should have continuity.

Kind of makes me wonder if it isn't just the relay. Those tend to be intermittent issues when they start going out.

 

[jvsutton]

Ok, just a note from my original post I already replaced the relay and it still acted up after that.

Yesterday I checked that the plug at the clutch had 12volts and I checked the continuity on the ground at the clutch plug and it was getting good ground. I also checked the continuity on the ground (pin 85) on the clutch relay and it was good too. The stupid thing has been working without acting up the past two days so I haven't been able to try the tap to see if it'll engage.

But for the resistance, I need to get some alligator clips for my multimeter because it's hard to reach down in the plug to touch the connectors with the little pointers. Anyway when I checked it I got varying results, I checked it multiple times trying to make sure I was touching, I got a reading of 5 one time and every other time I got a reading of 1.

 

[Zervun]

I'm having A/C issues as well (it stopped working when I replaced battery - old battery I could hear clicking).

I think mine is either the clutch or the diode. You might want to google those. You can get the clutch off of ebay (it is not that simple of a fix and need some special tools). The diode is super cheap, supposedly it can blow/crack - from what I have read it is down the wire from the plug to the clutch. You have to undo the wrap to find it.

It is my project for this weekend and I will take pictures if I find it.

 

[Zervun]

See my thread here - I fixed my AC it was the diode and not the clutch

http://www.ramforum.com/f62/ac_fuse_blowing_truck_running_rough_when_one-104159/

Not sure if that is yours but it's a ultra cheap and fairly easy fix

 

[jvsutton]

Well it finally messed up again on the way home yesterday. When I got home I got out to look at it and clutch wasn't spinning. I gave it a little tap and voila it engaged and started blowing cold. So I guess it's clutch replacement time. I think first I'll take the clutch front off and see if there are any shims in there that could possibly be removed.

Does anyone know what the gap spec should be on clutch?
EDIT: I found the gap should be.016-.031 inch consistent around the circumference of the clutch.


I don't want to go through the trouble of replacing the whole compressor and all that that entails.

 

[jvsutton]

Just a quick update. I took the clutch plate off and removed a shim and it has worked without issue. Hopefully it'll stay that way.