High Pressure In Air Con

Hi, I have been having trouble with my air con. The compressor clutch clicks on and out and if I tap it when it stops it starts up again. I closed the gap on the clutch and have now read I may need to replace the wiring loom, does anybody know where I can get one from? I have tried googling for it!!

Also, I bought a can of air con top up stuff from Halfords. When connecting to the system the gauge is up in the red showing high pressure, would this be the cause of my clutch randomly engaging and disengaging? Would I now need to take the car to a garage to have the pressure lowered?

What year of P38 do you have. The extra harness to improve voltage to the compressor was only up until VIN XA411503

This is the tech bulletin...








I would check out the clutch condition with a feeler gauge and then see where to go from there. If in doubt take it to an A/C specialist, dont keep messing with it, you will damage something and almost every bit associated with the A/C is expensive I would also be careful with those A/C refill things from Halfrauds, I dont know whether they put the right amount of oil in etc.

-Wills

a blocked condensor can give yer a high pressure or any contameenents in the system.

i have done this loom modification, i got it from land rovers for just over £50. it solved the problem of the clutch not engaging when it should. the gap in the clutch mechanism was down to it slipping due to lack of voltage holding it tight enough, the slipping wears it causing the gap to increase making the problem worse!
the main problem the loom sorts out is lack of voltage at compressor clutch coil. i had less than 11volt, the loom came with an additional relay and fuse for fuse box and took 40 mins to fit, its been wonderful ever since!
one thing i couldn't work out is the loom also comes with a large metal cased resistor! why if your upping voltage would you need a resistor?
anyhow it works a treat!

i cant see any reason why high internal pressure would hamper the clutch engaging, if you tap it and it engages its a lack of voltage, stick a multi meter on the two wires that disapeer under the pulley on the compressor and see what voltage is present!

redrange said:

one thing i couldn't work out is the loom also comes with a large metal cased resistor! why if your upping voltage would you need a resistor?

Click to expand...

That's to do with fooling the HeVAC that the clutch is engaged. If it wasn't there you would get the handbook up, not sure what the fault would be logged as though, compressor short circuit or something.

Basically the HeVAC unit needs to see a load on the compressor +12v line to know that the compressor has engaged.

When you install that harness instead of the HeVAC ECU directly powering the clutch it now instead powers the relay which in turn powers the clutch. The electrical load from the HeVAC ECU has now dropped and as such it would think there is a fault, the big 'heatsinked' resistor overcomes this problem by fooling the HeVAC ECU that there is actually an electrical load on the line and as such it wont bring the book up, and, in turn, still run the A/C properly!

Hopefully that answers your question and you can decipher my sort of backwards way of explaining it

-Wills