2016 Cascadia DD13. No power to Air Compressor.

Discussion in 'Freightliner Forum' started by Forever237, Jun 2, 2023.

  1. Forever237

    Forever237 Light Load Member

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    May 29, 2016
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    Hello, good folks,
    Have no power going to AC compressor.
    Checked compressor clutch - turns freely (when off).
    Check resistance on compressor connectors - has resistance.
    Clutch was not engaging with AC on and off whatsoever.
    Check low/high pressure - stable at ambient temperature (the correlated low pressure tube psi and ambient temperature). Checks out.
    I don’t think I have any leaks.

    Power to clutch has no voltage whatsoever. Tried with ignition on, engine on, ac off / ac on. Can’t freaking find a fuse or relay to that power. Why am I not getting power to ac compressor/clutch.

    I don’t know what else to look for. Anyone has any advice? Thank You
     
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  3. Smellfunny

    Smellfunny Road Train Member

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    I had one in recently that was not getting power to the clutch and it was the TRANSDUCER switch on the a/c line near the dryer. I could move it around and it would run. I just installed a new transducer and harness end and that took care of it.
     
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  4. AModelCat

    AModelCat Road Train Member

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    If static pressure is above say roughly 50 PSI high and low, start at the clutch, work back from the clutch until you find power.
     
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  5. Rideandrepair

    Rideandrepair Road Train Member

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    Might be a bad pressure switch. Probably located on the dryer. Can be changed without losing any refrigerant. It’s a common thing. I’d change it, and if that’s not the problem, leave it, keep the old one for future quick diagnosis. You can try unplugging it, and jumping the plug with a paper clip. Might work. Sometimes the plug itself goes bad. I just had to replace mine. Next on the list of suspects is the temp sensor probe. Located inside the cab. Small sensor with a wire probe going into the a/c evaporator. Those two things control power to compressor. Your Truck may be different than mine. Fuses etc. Mine also has a constant power supply wire running to it that comes from the starter. The plugs themselves at compressor seem to go bad, from heat and excessive movement from the fan engaging.
     
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  6. snowwy

    snowwy Road Train Member

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    What does stable at ambient temperature mean?

    That don't tell the people anything
    And that's not how it works

    If you got less then 50. The low pressure won't kick on. If you got too much. The high pressure won't kick on.
     
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  7. Forever237

    Forever237 Light Load Member

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    Thanks Everyone,
    Spent whole day yesterday trying to figure out under blazing heat. Turns out power line to compressor was corroded from rubbing back n forth underneath the engine.
     
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  8. Forever237

    Forever237 Light Load Member

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    As I understand it correctly, both Low and High pressure ports should be equal psi, ac disabled.
    There is certain correlation between outside (ambient) temperature and pressure at this ports (I don’t know but guessing freon expands faster than air). Attached photo. So if the correlation is off, you either have low/high amount of freon.
    That’s what I understood yesterday, scrolling through internet. Correct me if I’m wrong
     

    Attached Files:

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  9. snowwy

    snowwy Road Train Member

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    Pressure stabilizes when it's off. YES.

    But takes awhile these days.

    Correlation with ambient Temps. YES. It expands and contracts with temperature. My car reads 120psi equalized in july. 5psi in January.
    So cars don't run the compressor with defroster in the winter. Not enough pressure.

    That's why it's always best to leave ac alone till it gets warm. More accurate pressures in the heat. I donate my freon to people needing top offs. I buy the 30 pound containers. But wait till it's at least 80*

    Putting all that aside. You're asking for help. And saying it's copesthetic with ambient Temps tells the people NOTHING. It still boils down to 2 posts mentioning numbers.

    What's your EQUALIZED pressure. And posting that number.

    If you don't have enough. It won't work.
    If you have too much. It won't work.

    There's a minimum and maximum and neither side cares about ambient Temps.

    I can't say for sure as I live in dry air. But humidity might play a part also.

    On that note. Start with posting equalized pressure. And the forum can go from there.

    In the motorcycle forum..they have good compression. Good compression. WTF does that even mean? How do you know you have good compression when you don't even know what it should have.

    Anything short of factory spec is not good compression. 100 out of 170 is definitely not good compression. That cylinder is almost dead.
     
    Last edited: Jun 3, 2023
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  10. Forever237

    Forever237 Light Load Member

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    I found high pressure sensor. When disconnected (unplugged the elec current), fan started spinning fast which I guess meant it was working fine. I went through all fuses including trailer lights in engine bay (all of them were fine). Pissed me off they don't have relay or fuse there to diagnose (but again, this is first time i'm trying to fix my AC myself). Like I mentioned above, power line was corroded. Had no zip tie to secure the movement.
     
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  11. Forever237

    Forever237 Light Load Member

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    I compared the PSI reading to my friends truck at static. Both trucks were parked overnight with engine off. I bought one of those Arctic Freeze A/C Recharging Kit around $45 with minimum detail (upto 100 in multiples of 10 and goes red) pressure reader. Both trucks read about the same psi.
     
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