A.C. Just Quit Blowing Cool Air! 05 CTD Ram

Discussion in 'Dodge 3rd Gen Cummins 5.9 (24v)' started by Eightballsidepocket, Mar 10, 2007.

  1. Eightballsidepocket

    Eightballsidepocket Well-Known Member

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    Barely have any miles (19k) on my 05 long bed 4x2 CTD ram.

    The wife and I was dropping off our new Travel Trailer at our storage place today, and then on the way out of the place, I pushed the little snowflake/AC button, and had the fan on, and the temp set on cold. I got just warm, outside air.

    Normally you hear the A.C. clutch engage, but each time I pushed the snowflake button on, there was no clunk sound that I and all you folks are so used to hearing.

    I checked the HVAC fuse/ok, AC clutch fuse/ok, and finally the AC clutch relay/ok. I swapped that relay with my wiper relay(both were the same model number/identical rated relays) that I knew was ok, and no cold air.

    I swapped the wiper relay back to it's spot and the AC Clutch relay back to it's spot. Anyway, each time I pulled the relay and re-inserted it, and then hit the A.C. snowflake button, I'd hear a little click under the hood, and I'd get a momentary puff of cooler air, and then the air vents just put out warm, outside air as before.

    What might be the problem? When I turn on the fan speed switch with the A.C. "on" there is no change in engine speed or "clunk" sound of the A.C. clutch engaging. Neither does the "clunk" sound happen or Clutch engagement when the fan is in one of it's speed positions, and I press the A.C. on/off button back and forth.

    I'm still under warranty until August 2008. I will be calling my dealer's service folks Monday morning for a warranty visit.

    Thought maybe one of you folks had a similar problem and I'd get advice on how to fix it myself if it was simple? It'd save me the warranty trip.
     
  2. whiterocket5.9

    whiterocket5.9 Well-Known Member

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    ive experianced warm air blowing out of passenger side vents a few different times, i thought my brother was crazy when he said it because driver side had cold air comin out, no idea a gremlin i guess. for your problem im not sure maybe a wire came undone.
     
  3. Eightballsidepocket

    Eightballsidepocket Well-Known Member

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    Got an A.C. trouble shooting appointment with my Dodge dealer tomorrow/Tuesday, plus an oil change too.

    Thanks for the input.
     
  4. whiterocket5.9

    whiterocket5.9 Well-Known Member

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    cool, hope its nothign major
     
  5. Full Pull

    Full Pull Well-Known Member

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    sorry to here that I have never hade that prob. maby you have a coolant leak if it goes below a certin point it will not engage the Clutch. iam sure the dealer will take care of it. did you try putting it on recurlate not out side but inside cab air?
     
  6. Full Pull

    Full Pull Well-Known Member

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    also try putting it on the defrost setting see if your cluch will click on.
     
  7. Eightballsidepocket

    Eightballsidepocket Well-Known Member

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    Well, here's the results of the Dodge service visit today:

    The system was a little low on 134A refrigerant, but they think that it's the "Pressure Transducer Switch", that's faulty or working part of the time.
    The system seems to be leak-free otherwise. Even though my refrigerant was down 1/2 lb. from full, the tech said that some units come from the factory without being fully loaded with the refrigerant.
    *****
    Anyone know exactly what the Pressure Transducer Switch does in the A.C. system? I do know that it has something to do with turning on and off the A.C. clutch on the compressor or cycling the compressor.
     
  8. whiterocket5.9

    whiterocket5.9 Well-Known Member

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    i think it has something to do with transducing pressure when ya switch it :popcorn: honestly i have no idea
     
  9. Full Pull

    Full Pull Well-Known Member

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    is their any thing on line maby a chiltons manual . hope this helps F/P
     
  10. RJF's Red Cummins

    RJF's Red Cummins TRC Staff Moderator

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    Pressure Transducer Switch in most likely lamens terms....

    Low pressure cut off switch. That is my best guess, and a low pressure cut off switch will not allow the pump to engage once freeon has depleted past a certain level or pressure. It's designed for when you loose all your freeon, that is keeps the pump from running and burning up since it takes freeon to move the oil and make it airborn in the system.

    I think your system holds 1.6lbs, most likely. Being down a 1/2lb is a fair amount, but likely not enough to cause a too low of pressure situation and allow the pressure switch to do it's job.

    Here's a trouble shoot you can do, (I've never done this on a computer controlled vehicle, but the sensor is likely still the same). On these newer vehicles you've got to check clutch wire voltage with it running, due to that the ECM will not allow the pump to engage without the engine running, or until oil pressure is seen from the engine(my A/C comes on EXACTLY when my oil pressure guage jumps from start up). You'll want to be carefull because of the fan. Test your voltage at the wire's plug where it goes into the pump clutch. It will most likely not show 12v as I highly doubt something is actually wrong with the magnetic clutch itself, but could possibly happen.

    Once you have established NO voltage at the pump clutch, find your pressure switch (it's likely somewhere near the dryer, big black canister), unplug it, take a short piece of wire with the insulation stripped off a 1/4" from each end, and stick each end into the sensor plug that is connected to the wiring harness.

    How that sensor works, is when normal pressures are apparent, the switch allows electricity to run from one prong (the sensor should be a two prong plug), and to the other side to the second prong making a circuit. When pressure drops to an unsafe level it opens the circuit and won't let electricity pass through to the second prong, and blocking voltage to the pump clutch, disabling it.

    When you put the wire into the plug, you are making a closed circuit and should make the system work. If your pump clutch now engages with your homemade sensor (the wire) then it's almost for sure the sensor switch itself.


    The best overal option is to just take it to the dealer and say "here, fix it."
     
  11. Eightballsidepocket

    Eightballsidepocket Well-Known Member

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    It was replaced on Monday at the dealer. So far, nice cool air blowing from the vents.
     
  12. RJF's Red Cummins

    RJF's Red Cummins TRC Staff Moderator

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    Then there was your problem.
     

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