Air conditioner problems

[fritzimax]

I have an 03 with about 65k miles on the clock this past summer I have had nothing but trouble with my trucks air conditioner. The AC workers fine while the trucks engine is cold, after the truck warms up the AC no longer works. My mechanic changed the pressure switch and has determined that the AC clutch is in working order. After the pressure switch was changed it did work when the engine was warm for a few weeks, but then went back to only working when cold. When the AC does not work there is no power going to the clutch. I also need to mention that still having the original batteries in the truck I installed new ones this spring to be on the safe side and I think the problems with my AC started after the swap. Could it be a computer issue? Did I mess something up?#@$%!

If anyone has had a similar problem I could really use help with diagnosing this problem. Though the summer is now long gone and AC is not really needed here in the northeast it does also help with reducing moisture on the windshield when in defrost mode.

I thank all those who reply.

 

[Lordsman]

What are the guage readings when it warms up and is running? If its running and the head pressure gets way too high you may have non-condensibles(air, etc) in the system, an over charge, or dirty condenser coil. I'd ask the mechanic about this. You may have to remove the charge, pull a vacuum, and weigh in a correct charge. Not really enough info to diagnose it.

 

[Bill Stockard]

Try cleaning the connections on the Powertrain Control Module (PCM). The PCM receives low voltage signals from the A/C Pressure Transducer and in turn activates the A/C Compressor Clutch Relay located in the Power Distributiion Center (PDC). You might also check the A/C Compressor Clutch Relay. All three of these controls have to functrion properly to energize the A/C compressor clutch.



Bill

 

[fritzimax]

Thanks for the replies, the AC clutch relay had been swapped and the mechanic states that the pressures are within specs. According to his diagnostic scanner when the AC does not work there is a bad ground but he cannot find out where and why. If you ground the AC clutch relay the clutch engages. I will try cleaning the electrical connections and see if that helps. Could the new pressure switch he installed be defective too? (doubtful)

Thanks for your help.

 

[rashwor]

Sounds to me like you found the problem, a bad ground. I suggest cleaning all the wiring connections concerning the AC compressor and PCM. My guess is this will solve the problem since it is most likely a bad ground.

 

[fritzimax]

It's now March in about 3 months I will need the air conditioning again. To recap, I have had trouble with the AC not working once the engine compartment gets warm. Now the AC does not come on at all. When I press the button it lights up but the compressor does not kick in. My mechanic changed the pressure switch last summer, once changed the AC worked fine for a few weeks then it only worked intermittently for a few weeks and now nothing. The AC clutch was checked and it is not getting power. My mechanic said that the AC system has a bad ground somewhere but he can't find where. The AC clutch relay has been Checked too. If anyone has any ideas I could really use the help. I lost my job of 18 years awhile ago and can't afford to spend a fortune on diagnosis or repair. If I can't figure it out I will just have to go without.

Thanks to all who reply.

 

[B.G. Smith]

Is the pressure switch you are referring to mounted on the receiver/dryer? And yes, the switch could be bad. The no ground the mechanic talkes about may be the trigger signal/circuit to the AC clutch relay? That could be the pressure switch open? Sometime in the early 3rd generation they installed a thermister on the face of the evaporator to prevent freeze up, (ice forming on evaporator causing loss of air flow). If your year model has that it could also be the problem. bg

 

[RDeFayette]

Is the pressure switch you are referring to mounted on the receiver/dryer? And yes, the switch could be bad. The no ground the mechanic talkes about may be the trigger signal/circuit to the AC clutch relay? That could be the pressure switch open? Sometime in the early 3rd generation they installed a thermister on the face of the evaporator to prevent freeze up, (ice forming on evaporator causing loss of air flow). If your year model has that it could also be the problem. bg

Fritzimax,

Went through this with my '03. Thermister/Sensor on the evaporator was bad.

Here is the Dodge part number problem is as you can see it is only serviced with the evaporator. This from the Dodge parts book.

05073970AA SENSOR, Evaporator Fin Probe, Serviced with Evaperator, (NOT

SERVICED)

BUT if you want to give mine a try I'll send it to you.

My '03 was totaled last March and I bought it back and stripped it.

Kept EVERYTHING that was still good. still have the sensor.

One way to check is to turn the A/C on run it 'til it stops working.

Then turn the heat on to thaw out the evaporator. (about 5 minutes depending on the outside temp).

Then turn the A/C back on. If it works good shot it's the evap. sensor.

Bob

 

[goodguys75]

The a/c on these trucks are junk... . no mystery there... #@$%!

 

[fritzimax]

Thanks for the replies, I can't get the AC to work at all, could that thermistor sensor go bad and cause the system to not work at all? I will have to

look into that.

RDeFayette sorry to hear you totaled your truck, I hope there were no injuries, vehicles can be replaced. How hard is it to change that sensor?

Thanks, Pete

 

[RDeFayette]

Thanks for the replies, I can't get the AC to work at all, could that thermistor sensor go bad and cause the system to not work at all? I will have to

look into that.

RDeFayette sorry to hear you totaled your truck, I hope there were no injuries, vehicles can be replaced. How hard is it to change that sensor?

Thanks, Pete

It's mounted/inserted into the evaporator. Once you get to the evaporator it's a piece of cake.

Check power to the clutch, fuses, relays. If the charge is low it won't run. My dad had problems with the AC/heat control/mode switch check power into and out also.

Thanks, luckily I was the only one in the truck. Technically I didn't total it! lol, now The guy that was driving the blue oval (Ford) truck that t-boned me doing 60 mph totaled it. I can laugh now. Yup, replaced it the '04.

If you want the trermistor/sensor let me know.

 

[B.G. Smith]

Thanks for the replies, I can't get the AC to work at all, could that thermistor sensor go bad and cause the system to not work at all? I will have to

look into that.

RDeFayette sorry to hear you totaled your truck, I hope there were no injuries, vehicles can be replaced. How hard is it to change that sensor?

Thanks, Pete

The clutch cycling switch in the side of the receiver/dryer can prevent the system from running. You can unplug the connection and bypass the switch with a small paper clip or other wire to see if that is the problem. The thermister breaks the circuit to the clutch at a certain temperature, if it fails it could also be the culprit. As RDeFayette stated, the thermister is a piece of cake when you gwet to the evaporator, however you have to just about remove the dash to get to the evaporator. Let us know what you find. bg

 

[RDeFayette]

Might want to get a reflash if you're sure this started after putting new batteries in, stranger things have happened needing a reflash.

 

[fritzimax]

Can anyone tell me is the air conditioner compressor controlled through the FCM ? I have tried everything to get my AC working. The last thing I did was to change the fuse box(PDC), but it did not help. My AC cuts out when the engine gets warm. I can manually ground the AC compressor relay and the clutch will engage. Once the truck cools down the AC will work again sometimes for 2 minutes sometimes for 20, I can't figure it out. Why is the AC compressor relay loosing the ground signal?
Thanks to all who reply.

 

[Prairie Dog]

Have you tried a different relay?

More than likely the relay has a diode in it. If that diode has failed then the "low" signal from the computer (ground signal) may not be strong enough to trip the relay anymore. Maybe there's another relay someplace you could swap it with?

You could disconnect the relay and use a DVM to measure between this ground signal and battery pos. If when AC is called for you don't see something close to battery voltage, then either the computer has a bad chip or the wire from the computer is open - maybe a damaged wire or corroded connection.

 

[fritzimax]

Yes, unfortunately I have tried that. One of the first things I did was to swap out the relay. I then had the system checked by my mechanic who installed a new pressure switch. I then spent several days taking the dash apart #@$%! to try a new thermistor that sits on the evaporator. Then when that failed I installed a new power distribution center( fuse box). When I did the fuse box I cleaned all the electrical connectors on the box and on the ECM on the side of the block. I have not yet changed the FCM which mounts on the front of the fuse box. I am not sure if the AC is controlled through that unit and at about $250 I don't want to waist more time and money switching that too. At least summer is over and here in the north east I won't need my AC until next year though it does help with defogging the windshield in the winter too.
Thanks again to all who reply.

 

[Bill Stockard]

See my original post #3



The A/C function is controlled by the Powertrain Control Module (PCM) via the A/C Compressor Clutch Relay. The PCM grounds the A/C Compressor Clutch Relay based on inputs from several switches including the A/C high and low pressure control switches. Ref: 2003 Dodge Truck Service Manual, page 24-13.



Since your problem appears to be heat related, I'd look for a failure inside the PCM which is located on the passenger side firewall and can be affected by the heat off the exhaust manifold and/or the exhaust pipe.



Bill

 

[fritzimax]

Bill,
Thanks for the reply. I have nothing mounted on the firewall on my truck, I do however have what I thought to be the PCM mounted to the drivers side block of the engine. If there is a problem in this unit I know of no way to check or repair it other than to have it either rebuilt (ebay $495) or replaced $???? Do you know of a way to test it? Do you know if the AC compressor runs through the FCM on the fuse box that part is only about $250?

Pete

 

[Bill Stockard]

I noticed you have a manual transmission; however, the Factory Service Manual makes no differentiation between a manual or automatic transmission in its description of the functions of the PCM. IIRC, manual transmission trucks incorporated many of the PCM functions into the Engine Control Module (ECM) which you correctly located on the driver's side of the engine block. In your case the proboem may be in the ECM and a fault occurs when the engine block heat warms the ECM. I don't know what service checks need to be performed to find the fault. Perhaps you could send a Private Message to either TDR members "Bob4x4" or "sag2" who are knowledgeable Ram truck techs.



Bill

 

[fritzimax]

My Ac is still not working, any new ideas? Thanks