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Pete 379 won't take AC charge

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Ccjohn, Jul 24, 2017.

  1. Jul 24, 2017 #1
    Ccjohn

    Ccjohn Bobtail Member

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    Trying to fix the ac on a 2001 Pete 379 with 48" sleeper. I got the system evacuated then I hooked a vacuum pump up to it. Brought it down to 30" of vacuum and it held there all day long no problem.

    Went to add 134a and it won't take more than .3lbs. (The truck doesn't have a sticker on it but it should take at least 3lbs). I'm adding it through the low side with the truck running. When I have about .3 one of freon in it both the high and low pressures are reading 50psi. I'm thinking I've got a blockage somewhere and it's not letting the freon through the whole system? Also I cannot get the ac compressor to engage. I've tried jumping the low switch and still it won't come on. Ideas?
     
    Ccjohn, Jul 24, 2017
    Ccjohn, Jul 24, 2017
    #1
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  3. Jul 24, 2017 #2
    GrapeApe

    GrapeApe Road Train Member

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    If I remember right, those have orifice tube in the front and an expansion valve on the bunk? The orifice tube should be visible by taking the line off at the firewall, the tube is in the end of the evap core. Check that that is not plugged up. Did you change the accumulator as well?

    What parts, if any, did you change? New compressors and evaporators come with rubber plugs under the metal cover for the ports. Were they removed?

    Could it be as simple as a bad schrader valve on the low side. Can you pull vacuum on the low side only?

    As far as the compressor, step 1 is to test the clutch by adding power and ground to it. If it clicks, you have a wiring problem, if not, bad clutch. That will give a direction to go there. Are you sure that you jumped the low pressure switch? Pete's usually have 3 switches, a low pressure, high pressure and a fan override switch. The low pressure switch should be on the low side line along the firewall.
     
    GrapeApe, Jul 24, 2017
    GrapeApe, Jul 24, 2017
    #2
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  4. Jul 24, 2017 #3
    Steelhauler1246

    Steelhauler1246 Light Load Member

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    Having the same darn issue with my 01 too !! Perfect time when it 98+ out here :mad:
     
    Steelhauler1246, Jul 24, 2017
    Steelhauler1246, Jul 24, 2017
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  5. Jul 24, 2017 #4
    Ccjohn

    Ccjohn Bobtail Member

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    Nothing was replaced. The ac in this truck hasn't worked for over a year. When i put the gauges on it the pressure was ~55-60 on both the high and low pressure sides. It was low on freon but still was holding so i decided to try and evacuate it, vacuum it down and try to recharge before I took anything apart.

    I tried charging it through the low side only with the truck running. The compressor clutch would not engage. When I charged it through the low side with the truck running the pressure on the high side matched what the low pressure gauge read. With the truck off I can vacuum or add freon to either the high or low side. Both gauges equal out at the same. Which is about 50psi

    I was thinking about taking the orphus tube out but figured I should start with the compressor clutch and see what happens after I get that working. I've got 12 volts at the compressor when I turn the ac on in the cab but it's not engaging/disengaging the clutch.

    Yes I did jump the low pressure switch. The original labels are on all the connectors.
     
    Ccjohn, Jul 24, 2017
    Ccjohn, Jul 24, 2017
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  7. Jul 27, 2017 #5
    Tug Toy

    Tug Toy Road Train Member

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    You have to close the high side gauge otherwise the freon just presurize back into the bottle..... back into the low side...... back into the bottle......


    It will never get higher than the bottle pressure. Close the high side gauge and it will start pulling it in.
     
    Tug Toy, Jul 27, 2017
    Tug Toy, Jul 27, 2017
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  8. Jul 28, 2017 #6
    Ccjohn

    Ccjohn Bobtail Member

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    The high side was closed.

    Pretty sure my problem lays with the compressor not turning on
     
    Ccjohn, Jul 28, 2017
    Ccjohn, Jul 28, 2017
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  9. Jul 28, 2017 #7
    GrapeApe

    GrapeApe Road Train Member

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    Even without the compressor, it should take more than .3 lbs though. I always charge through both with the truck off. It's very rare not to get a complete charge that way, but in those cases, I shut the high side valve and start the truck to pull that last bit through the low side.

    At this point I think you're on the right track, get the compressor running and go from there. You may have another issue though. That .3 lbs bothers me. I get .5 when I recover my hoses, so it seems that you aren't getting much, if any, to go in the system at all.
     
    Last edited: Jul 28, 2017
    GrapeApe, Jul 28, 2017
    GrapeApe, Jul 28, 2017
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  10. Jul 28, 2017 #8
    AModelCat

    AModelCat Road Train Member

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    Same here. I always charge through high and low at the same time with the engine off. I do it with vacuum still in the system and that helps pull the refrigerant in.
     
    AModelCat, Jul 28, 2017
    AModelCat, Jul 28, 2017
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  11. Jul 28, 2017 #9
    Ccjohn

    Ccjohn Bobtail Member

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    I agree the .3 seems like almost nothing. I've charged plenty of vehicles and trucks and never had an issue so I don't think my problem is with my procedure. I did charge it with a 30" vacuum on it
     
    Ccjohn, Jul 28, 2017
    Ccjohn, Jul 28, 2017
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