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P38A AC Issues

Discussion in 'Range Rover' started by Stevekennah, May 4, 2019.

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  1. pwood999

    pwood999 Well-Known Member

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    I agree with Data. If the compressor cuts in & out with the pressure switches bridged, then check if it does it with relay bridged. If yes, then the issue must be compressor wiring or clutch.

    Is the HEVAC early system without relay, or later modified version ?
    Do you have the correct control panel install ? (early panels don't like the relay installed because there's insufficient compressor clutch current )
     
  2. Grrrrrr

    Grrrrrr Jedwood Spannerhands

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    Post #4:

     
  3. Stevekennah

    Stevekennah Active Member

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    So how do you adjust the clutch then??

    I'm thinking about burning it at the moment, so frustrating
     
  4. Stevekennah

    Stevekennah Active Member

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    Also how do you test the compressor sensor ?
     
  5. tarphenry

    tarphenry Well-Known Member

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    If you download Rave it will have all info and help you to understand how it is wired and what controls what
     
  6. Stevekennah

    Stevekennah Active Member

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    Wiring diagram seems pretty simple, ACM checks sensors and then switches on, ECM then check Evaporator temp and grants the compressor signal........ Might check the HEVAC module tomorrow

    For anyone wondering the duel switch has a Schrader valve and can be changed with the system pressurised, the standard pressure switch does not and needs a depressurised system....... How stupid
     
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  7. pwood999

    pwood999 Well-Known Member

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    According to first post you can bridge relay 3 and compressor runs ok. . . . . so . . :
    • Relay-3 implies you have later HEVAC panel so it's not sensing compressor current.
    • At base pressure sensor-2 should be open circuit, and close when pressure rises to enable the fans. Trinary switch closes > 21 Bar to enable fast fan mode.
    • If AC gas is low trinary pressure will never close, but if pressure is marginal it will sometime s ! If gas is between 2.4 Bar (35 psi) & 21 Bar (305 psi) it closes to allow compressor to run.
    • Does your Lynx give all the sensors reading ? If so what are they ?
    Remember the HEVAC is 1990's software so will do strange things if one or more sensors are out of whack.

    Also, don't forget the system needs 1250-1400g AC gas during refill, compared to the 600-800g that most cars need.
    https://www.autoairconparts.co.uk/AC_Filling_Quantities_2016_EN.pdf
     
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  8. ukadamwest

    ukadamwest Well-Known Member

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    I was just going to post the same thing as pwood. if the pressure is low the pump shuts off. kwickfit, halfords and a couple of others will shove it on a diagnostics machine and not charge if a fault is found.
     
  9. pwood999

    pwood999 Well-Known Member

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    Plenty of US video on youtube about AC recharge. Not sure if it's good practice, but several show running the system with refill gauges connect & pressure changes when the compressor starts up . . . .could be triggering over-sensitive switches ?
     
  10. Stevekennah

    Stevekennah Active Member

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    Hi all,

    Still no joy, took my HEVAC unit and it states that the part number is AWR1012

    Can anyone confirm if this is correct or has some swine put an old HEVAC unit on a newer car??

    Thanks
     
  11. wammers

    wammers STILL BREATHING. Donater

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    If it has heated seats unit should be JFC102550. AWR1012 ended with Vin number TA344172.
     
    Last edited: May 14, 2019
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  12. Stevekennah

    Stevekennah Active Member

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    It has heated seats and the panel still states awr1012..... I'll check the vin now
     
  13. Stevekennah

    Stevekennah Active Member

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    Vin ends in 2A461696
     
  14. Datatek

    Datatek Well-Known Member

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    I don't think it's that easy as there seem to be several part numbers for the HEVAC. I assume yours has the heated seat buttons?
     
  15. pwood999

    pwood999 Well-Known Member

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    Grrrrrr likes this.
  16. Stevekennah

    Stevekennah Active Member

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    Hi Datatek yes my panel has the heated seat buttons
     
  17. Datatek

    Datatek Well-Known Member

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  18. Stevekennah

    Stevekennah Active Member

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    From reading that thread it looks like I have the wrong HEVAC unit and need part JFC102550
     
  19. pwood999

    pwood999 Well-Known Member

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    Bypass the compressor relay and see if it works when your panel actually senses compressor current. . You also need to check ambient temp sensor location but that can wait.
     
  20. Stevekennah

    Stevekennah Active Member

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    It's all very confusing..... Ambient temperature sensor is located to the left of the drier behind the bumper
     
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