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1992 L9000 Aeromax Cummins L10 AC question

Discussion in 'Trucks' started by PhoenixRising2015, Jul 16, 2017 at 3:09 PM.

  1. PhoenixRising2015

    PhoenixRising2015 Member

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    I am attempting to get the Air Conditioning working on our six wheeler dump. You can see from the pics attached someone attempted to bypass several components. It was working however after a bit it would sound like the high pressure switch was not kicking the compressor off, so we disconnect the belt.
    I see several components however I am not sure which is which and how to properly wire it back up. Any help you be great, I assume some components are bad. So once connected properly I will have to figure out which,

    1 FriewallComponents.jpg 2 ACPicts (3).jpg 3 ACPicts (2).jpg 4 ACPicts (9).jpg 1 FriewallComponents.jpg
     
  2. mitch504

    mitch504 Senior Member

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    That yellow switch is the high pressure switch. The other components you posted pics of are air system, not A/C.
     
  3. PhoenixRising2015

    PhoenixRising2015 Member

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    Thanks for the input, does the high pressure cycle the compressor clutch on and off during normal operation of the system, or is it a safety device? Also their are two sets of wires coming from the compressor, one set goes to the clutch I presume to cycle the clutch, but what is the second set for? The second set goes to the rear of the compressor.
    Would you know where I could get a wiring diagram for this system?
    Thanks
     
  4. Birken Vogt

    Birken Vogt Charter Member

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    The high pressure switch is a safety device. Never opens under normal operation. There will be a low pressure switch elsewhere, or a low temperature switch, to cycle the compressor.

    I don't know why the extra wires but maybe a picture of the compressor would tell the story. There is usually just power, or power and ground, to the clutch and that is all.
     
  5. Muffler Bearing

    Muffler Bearing Senior Member

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    Wow, wire nuts... that's never a good sign. Personally I would put the belt back on, leak test the system, fill it up and jump power and ground to the clutch. Then you know you actually have a system worth saving. The electrical can be the last problem you address. I'd hate to see you burn hours of diag sorting out wiring only to find a shelled compressor that plugged the evaporator, and condensor .
     
  6. Birken Vogt

    Birken Vogt Charter Member

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    Also, it would be worth knowing if this has been converted to R134a or not. Is it still full of R12 and asked, does it kind of work at all?
     
  7. DMiller

    DMiller Senior Member

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    I really hated seeing rats nests as these show up at my last garage, where do you start and how deep before gets too expensive? If I would do anything first would find out why that brake light/possibly low air switch is disconnected then move to AC. As to the AC, consider having the system purged, replace everything to accept R134A and update that machine and yes I know will be a chunk of change. Someone has been bypassing to make something that is probably screwed up to work where you will spend that level of funds or more just to make it functional but may not cool well.
     
  8. Birken Vogt

    Birken Vogt Charter Member

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    I disagree somewhat on 134a, so few R12 vehicles running any more that the price has generally dropped to a reasonable level, I would refill with R12 if it does not need major work, so that it continues to work as designed. There is always the element of unpredictability with a different refrigerant and a risk of damage from mixing however small. But it often tips the scales toward R12 at this point in history.
     
  9. PhoenixRising2015

    PhoenixRising2015 Member

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    I did hard wire the clutch and the system works, however the system is not cycling. where would the low pressure or low temp switch be on this Ford? Also see the picture below showing a wire to the back of the compressor. Anyone know what this is for?

    Agree with comments, this is a rats nest, however I (retired from 30 years as Electrical Engineer) am attempting to sort it out. I am doing this for my son who is getting his excavation business of the ground. So labor cost for Dad are very low --- All Comments are well taken thanks.
     
  10. PhoenixRising2015

    PhoenixRising2015 Member

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    I found this tag pictured below on the compressor, so I think it is converted to R134A which is a good sign. Dose anyone know where I could get a wiring diagram of this Ford? It would be helpful to figure out what/why was disconnected in the two pictures in my initial post. Is that sensor for low air? AcPicts m (6).jpg
     
  11. Birken Vogt

    Birken Vogt Charter Member

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    Interesting on the compressor. The other question is what type are the service ports? That will tell whether it has been converted.

    As for the clutch not cycling, is the unit freezing up? That is when the clutch should cycle, until then, it should stay on.
     
  12. Muffler Bearing

    Muffler Bearing Senior Member

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    Good to hear it is a functional system! Sorry I can't think of any source for wiring diagram. Just a thought, I have encountered systems that don't cycle the clutch. The clutch stays on, but they cycle the engine fan. Any chance you have this style?
     
  13. Birken Vogt

    Birken Vogt Charter Member

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    The engine fan cycles on high condenser pressure. The clutch cycles on low evaporator pressure or temperature. They also make variable compressors that could mean there would be no clutch cycling but I have never seen one on a big truck. If a clutch never cycled on a fixed displacement compressor it would surely freeze the evap on low speed settings.
     
  14. PhoenixRising2015

    PhoenixRising2015 Member

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    forgot to attach the picture on the initial post -- here it is AcPicts m (8).jpg