HDi Dash Light Chasing and Air Con fault

[Rhothgar]

I am putting the red light on the temperature gauge, rightly or wrongly, down to the air con not working.

Read an interesting post on here about the Air Con ECU not have a dialogue with Lexia. Whatever I do, mine will not come up. I am left wondering particularly in light of my next comment whether Citroen just ended fitting a different Air Con ECU that what the VIN is registered to and hence Lexia will not pick up something that it is not linked to. Having said that, I have changed the main ECU and soldered the old immobiliser chip across, it wonder if there is an IC inside the main ECU that contains information about what Air Con system is installed?

Looking at the factory manual there are four pins going to the air con relay but with 5 wires connected (2 going into 1). However, mine doesn't have that. It has 4 pins and 4 wires. I assume the 2 going into 1 is supposed to be the high load side.

Anyway, the clutch doesn't engage. I have tried bridging the high load with a paperclip and even applying direct battery voltage from the battery so I am guessing this means the compressor either needs replacing or a shim removing to get the pulley closer to the clutch.

I assume the Pressostat is the cylinder on top of the offside wing on an HDi Xantia. Is this right? If so, is that technically the trinary switch? I get 13V on pin 3 which is from the fusebox and also 13V on Pin 1 which comes from the air con ECU. I assume therefore that this means the Air Con ECU is live?

The temperature gauge inside the cabin does not show the outside temperature anymore and needs replacing. Does this mean that the air con would not kick in if the ECU doesn't receive that information? One would think that it would have a default mode to run even if this is not working. Could I put a resistor across the wires to fool it into thinking the outside temperature is 30 degrees does anyone reckon?

Stupidly, I bridged the low side wires on the air con relay connector yesterday and am left wondering if I have blown something. I am sure I was seeing 13V on 3 pins at one point...

[Rhothgar]

Another check I have done which I read on the general internet is that the clutch coil for the air con should read between 2 - 5 Ohms.

Mine is reading 40 MOhms.

It's quite easy to measure. Would someone with a working air con mind checking their coil resistance please and reporting what it gives? Mine is a two pin white connector just under the air con compressor with a blue wire and a green wire with yellow dots.

[admiral51]

Found This Post not sure if you have seen it, may have some info for you

[Rhothgar]

That's awesome.

Thanks Colin.

Not sure it is my issue as I measured the compressor coil at 40 MOhms but definitely worth a check. I think it might have been you that posted that fix for the fusebox a while back. That was a Godsend.