P38A AC Issues

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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 )
 
pwood999 said:
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 )
Click to expand...

Post #4:

Stevekennah said:
Controller is original
Click to expand...
 
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
 
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
 
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.
 
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 ?
 
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
 
Stevekennah said:
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
Click to expand...
If it has heated seats unit should be JFC102550. AWR1012 ended with Vin number TA344172.
 
Last edited:
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.
 
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