HEVAC Operation - Low Ambient Temps

[p38arover]

I've been trying to help a bloke out with his air con compressor clutch not staying engaged.

I couldn't see any reason based on what he was telling me.

However, tonight he told me his local temperatures have been between 0 and -3 deg C. He is in far western Ireland and his nearest dealer is 6 hours away.

I wonder if the P38A HEVAC panel won't switch the compressor on if the ambient temp is low. After all, why would it need to?

[Junosi]

I was working on my A/C clutch a couple of weeks ago and noticed that even with my HEVAC reading HI/HI the compressor was still coming on. Maybe for dehumidify purposes ?

I saw there was a factory recall or recall kit for the early clutch problem. From what I could gleen it was basically another relayed circuit to provide better voltage to the magnet that pulls the clutch on to the faceplate. Thought I'd make my own up if my shim removal and filing doesn't work out well.

[p38arover]

I was working on my A/C clutch a couple of weeks ago and noticed that even with my HEVAC reading HI/HI the compressor was still coming on. Maybe for dehumidify purposes ?

Yes, I had considered that. I can't find any reference to it yet.


I saw there was a factory recall or recall kit for the early clutch problem. From what I could gleen it was basically another relayed circuit to provide better voltage to the magnet that pulls the clutch on to the faceplate. Thought I'd make my own up if my shim removal and filing doesn't work out well.

I fitted that kit to mine. I had tried a simple relay connection but it appears there may be some sort of current sensing, The clutch would activate for a few seconds then switch off. I haven't really looked hard at the circuit but for some reason there is a high power resistor with a heatsink in the circuit. Maybe to emulate the current draw of the clutch?

[fraser130]

it appears there may be some sort of current sensing, The clutch would activate for a few seconds then switch off. I haven't really looked hard at the circuit but for some reason there is a high power resistor with a heatsink in the circuit. Maybe to emulate the current draw of the clutch?

Ron, that sounds like a possibillity, Perhaps he can put a brake light bulb in parallel(?) with the clutch to see if that makes a difference?
Maybe run the heater till the interior is stinking hot too?


Fraser

[Scouse]

Ron, there's nothing that I can find in any bulletins or manual referring to anything that would be affected by low outside temperatures :(.

The workshop manual does mention that a replacement HEVAC ECU needs to be initialised with Testbook - you mentioned that he'd tried another one - but I doubt that would bring up the error described.

[p38arover]

Thanks for looking Scott.

I think the initialisation is to reset the blend flaps, etc.