Doolinjames
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Rl 13 and 14
P38 Air Con Clutch Not Engaging
- Thread starter Radar1946
- Start date
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Doolinjames
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- denny
Can I cross the wires on the relay to c if the clutch comes on
Doolinjames
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- denny
These green relays R 5 pins
Doolinjames
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Ywb 10031 are the part num
You could do it at the clutch with a 12v supply and earth, (testing purpose only) 1 pipe will get cold pretty quick if it has gas.
But first did it work and when?
Why do you think the relays are duff?
Are you getting a supply to the relay and a signal to switch?
Does it actually have gas cos if it doesn't it wont switch on.
J
Doolinjames
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Yes I put gas into the system
Doolinjames
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My relay tester says they R duff
Doolinjames
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That's if it's working ok.the 4 pin relay tester is working ok.but the 5 pin every relay I check they are duff surely they can't all be duff.
What relay tester is this? if the tester says they are duff then get some new relays, then move to the next inline.
Ahhhh
.So back to basics do you have the rave wiring diagrams for the AC.
Test the clutch at the clutch and check it gets cold. Then work back. there is a pressure switch down by the drier that seems to fail. 3 way switch, trinary switch, pressure switch, or something.
See if you are getting a signal at the relay to tell it to switch.
J
Doolinjames
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OkWhat relay tester is this? if the tester says they are duff then get some new relays, then move to the next inline.
Ahhhh
So back to basics do you have the rave wiring diagrams for the AC.
Test the clutch at the clutch and check it gets cold. Then work back. there is a pressure switch down by the drier that seems to fail. 3 way switch, trinary switch, pressure switch, or something.
See if you are getting a signal at the relay to tell it to switch.
J
Datatek
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Those are the fan relays, relay 3 is the one in the clutch circuit plus F27. Use a test lamp to check for 12 volts at the relay or you may damage the HEVAC aircon output. What year is your car? The most common cause of the aircon clutch not engaging is low gas pressure, personally I have never know the trinary pressure switch to fail but of course that could be the problem, check for 12 volts on the input and output of the switch.
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I have a vague memory of a post on RR.net of someone shimming the air-con compressor on some years. Never had any issues with mine other than the TXV failing so it vents the gas.
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Quick check is to apply 12V directly to the compressor clutch to see if it engages. It's a 12V device, so should not cause any issues.
The clutch circuits are simple. Early version doesn't have Relay-3, the later cars do. In both cases the AC Gas pressure should be between 2.4bar & 21bar. The dual pressure switch cuts the clutch with either Low gas, or Excess pressure to prevent damage.
Just trace the voltages on the wires !!
The clutch circuits are simple. Early version doesn't have Relay-3, the later cars do. In both cases the AC Gas pressure should be between 2.4bar & 21bar. The dual pressure switch cuts the clutch with either Low gas, or Excess pressure to prevent damage.
Just trace the voltages on the wires !!
Doolinjames
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Well yesyi. Took out the 2 green relays for the aircon.i started the car aircon pump works switched off on the dash.it stopped switched back on nothing?
Datatek
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The 2 green relays are not for the aircon, they are for the condenser fans. I suppose you know that if the aircon switch light is on, the aircon is off.
Maybe because the fans didn’t come on the pressure got to high so wouldn’t switch to allow. (I don’t know)
Great diagnostic testing btw
J
A few quick things...undo the circular plug and put 9v across the terminals...doesnt matter which way round, and 12v is not required. Does the clutch pull in? If no, does it at least magnetise...( test with spanner..). If you hit the clutch with a spanner does it pull in? If the answer is yes, but it's a bit hesitant, then get some filter paper in between the clutch linings and clean out the layer of dirt and oil. If that still doesnt work you may try to separate the clutch and remove a shim to close the gap... If however the clutch is physically working ok then you need to get the etm and work back from the compressor through the various wires switches to work out where the signal is getting lost. My prev p38 did not get a low signal back to Hevac from the ecm (ac grant) in response to the ac request, and in the end I had to permanently earth that wire in the footwell to compensate. Hopefully yours will be less painful.
