Sorry for the long post ... it took a lot of words to describe my problem, lol

Hi all ... I am hoping that someone can help me with this problem because I am totally stumped. I have searched through numerous threads and found a lot of similar problems but nothing exactly the same as mine.

So if I start the truck up and then fire up the A/C it usually works for a few minutes. It blows nice, cold air. Then, all of a sudden, the air will get distinctly very humid and warm. Now I have tried for weeks to find out exactly when this occurs, but it appears to be random.

At first I thought that it was working while I was driving fast and not working at slower speeds / idle. I have proved that wrong, however, because lately it doesn't even work on the highway at 65. What does work is that when I'm driving along and the A/C cuts out, I just press the button to turn it off, let it stay off for about 5 minutes, then turn it back on and I get a few minutes of cold air again.

I thought that I had the same problem described in this post:
https://dodgeforum.com/forum/3rd-gen...ditioning.html
However, I checked and my condenser fan is running good.

Also, I know my R134a charge is correct, I had the system purged and recharged and still nothing.

Any ideas are greatly appreciated!!

 

maybe the expansion valve is sticking. maybe the clutch on the compressor is having a hard time reengaging.

 

i had the same thing happen in a 99 ram that i had and after i hit 300k mi i traded it and never found out what was causing it but same thing turn it off and then back on it would work

 

thanks guys ...

snidehockey: is there a way I could determine if any of those problems are actually occurring? Would the condenser fan run even when the compressor is not running?

 

Is it doing it at a specific RPM? Does it do it while you are just sitting still in park? It sounds like something is disengaging it somehow. The first two places I would look would be:
- The electrical connections: you may have a loose wire somewhere that is semi connected. My sisters truck did this after she had a ne cd player installed as they pulled on a wire and it was barely connected so every so often if the wire would rattle or move any her ac system would blow hot air or no air at all.

- The ac Compressor clutch: Pop the hood and start the truck with it off and watch the clutch, then have someone turn on the ac and see if it engages (not sure if you can see it on our trucks as I haven't really looked at it, I know you could see it engage in my old truck though) then wait a while and watch it to see if it disengages at any point.

Other than that though Im not to sure what it could be...

 

pop the hood when it does that and see if any of the ac lines get frost on them, if a line if freezing it probably has a restriction in it causing the ac to work for a bit then stop working when it freezes till it defrosts then it starts working again. Probably right around the orifice tube. Other than that I would check pressures and see what they are doing up till it stops working. How do you know it has the correct charge?

 

I know it has the correct charge because I just had the system purged and recharged. I had to disconnect the lines when I changed my heater core. (This problem was happening before I disconnected the lines so that didn't cause this) ...

EDIT: After my friend vacuumed and filled my system with 1lb 7oz I double-checked the pressure with my A/C gauge and it was in the acceptable range.

OK so here is where I am after another day of investigation. I found that I can run the A/C when the truck starts and what is happening is that once it reaches a certain temperature in the truck after a minute or two then it stops working. So here is my theory ... I think that the compressor clutch is sticking or not re-engaging properly. I am guessing that once the temperature in the truck satisfies the thermostat, the system disengages the compressor for a few minutes and then when it goes to re-engage it, it fails to engage. At this point (as soon as I feel the humidity) I switch the system off, wait about 5 minutes and then turn it back on for another few minutes of cold air

So I guess I need to verify that the clutch is not working ... I will try to take a look at that later today. Has anyone ever replaced the compressor clutch before? Is it a hard job?

 

Its been a few years (and with a much older truck) but when I replaced mine I believe there was a center nut that needed removed and then I needed a pulley remover to get it off. I really haven't had the need to really look at what the truck has on it now so it may be simpler than that.

 

Heres a good link to what you would need to do with pictures as well to help out....



http://images.google.com/imgres?imgu...US272%26um%3D1

The refrigerant system can remain fully-charged during compressor clutch, pulley, or coil replacement. The compressor clutch can be serviced in the vehicle.

REMOVAL:

Disconnect and isolate the battery negative cable.
Unplug the compressor clutch coil wire harness connector.

Insert the two pins of the spanner wrench (Special Tool 6462 in Kit 6460) into the holes of the clutch plate. Hold the clutch plate stationary and remove the hex nut.

Remove the external front housing snap ring with snap ring pliers.

Install the lip of the rotor puller (Special Tool C-6141-1 in Kit 6460) into the snap ring groove exposed in Step 6, and install the shaft protector (Special Tool C-6141-2 in Kit 6460).

Install the puller through-bolts (Special Tool C-6461) through the puller flange and into the jaws of the rotor puller and tighten. Then the puller center bolt clockwise until the rotor pulley is free.

Remove the screw and retainer from the clutch coil lead wire harness on the compressor front housing.

Remove the snap ring from the compressor hub and remove the clutch field coil. Slide the clutch field coil off of the compressor hub.
INSPECTION:
Examine the friction surfaces of the clutch pulley and the front plate for wear. The pulley and front plate should be replaced if there is excessive wear or scoring.

If the friction surfaces are oily, inspect the shaft and nose area of the compressor for oil. Remove the felt from the front cover. If the felt is saturated with oil, the shaft seal is leaking and the compressor must be replaced.

Check the clutch pulley bearing for roughness or excessive leakage of grease. Replace the bearing, if required.

INSTALLATION:

Install the clutch field coil and snap ring.
Install the clutch coil lead wire harness retaining clip on the compressor front housing and tighten the retaining screw.
Align the rotor assembly squarely on the front compressor housing hub.

Thread the handle (Special Tool 6464 in Kit 6460) into the driver (Special Tool 6143 in Kit 6460).

Place the driver tool assembly into the bearing cavity on the rotor. Make certain the outer edge of the tool rests firmly on the rotor bearing inner race.
Tap the end of the driver while guiding the rotor to prevent binding. Tap until the rotor bottoms against the compressor front housing hub. Listen for a distinct change of sound during the tapping process, to indicate the bottoming of the rotor.
Install the external front rotor snap ring with snap ring pliers. The bevel side of the snap ring must be facing outward. Press the snap ring to make sure it is properly seated in the groove.
CAUTION: If the snap ring is not fully seated in the groove it will vibrate out, resulting in a clutch failure and severe damage to the front housing of the compressor.
Install the original clutch shims on the compressor shaft.
Replace the compressor shaft hex nut. Tighten the nut to 10.5 foot pounds.

Check the clutch air gap with a feeler gauge. If the air gap does not meet the specification, add or subtract shims as required. The air gap specification is 0.41 to 0.79 millimeter (0.016 to 0.031 inch) . If the air gap is not consistent around the circumference of the clutch, lightly pry up at the minimum variations. Lightly tap down at the points of maximum variation.
NOTE: The air gap is determined by the spacer shims. When installing an original, or a new clutch assembly, try the original shims first. When installing a new clutch onto a compressor that previously did not have a clutch, use 1.0, 0.50, and 0.13 millimeter (0.040, 0.020, and 0.005 inch) shims from the clutch hardware package that is provided with the new clutch.
Reverse the remaining removal procedures to complete the installation.
Clutch Break-in:
After a new compressor clutch has been installed, cycle the compressor clutch approximately twenty times (five seconds on, then five seconds off). During this procedure, set the HVAC control to the recirculation mode (Max-A/C), the blower motor switch in the highest speed position, and the engine speed at 1,500 to 2,000 rpm. This procedure (burnishing) will seat the opposing friction surfaces and provide a higher compressor clutch torque capability.

 

thanks for the instructions!!! ... I am going to take a peek at it after work tonight and see what it looks like.

I'll let you know how it goes ....