C2 1.6 VTS and AC compressor not engaging

[d-iivil]

Hi all!

I've spent past week googling around and finding no luck with my issue, so I decided to register here and ask if someone could help me

So the problem is that the AC compressor on my C2 will not engage. Here are things that I've checked so far:
- AC system tested for leaks and filled with fresh gas
- No error codes anywhere when checked with Lexia (not sure if I checked them from correct place, help required for this too)
- Radiator fan works ok, it starts to spin as soon as I press AC button on the control panel
- Analog style control panel with no digital controls, manual AC, back lights etc works
- Blower works ok on all speeds

Then some things I have measured...

I unplugged the connector on the right and there was no power between those two pins. I think there should be 12 volts when AC is turned on that would engage the compressor's magnetic clutch?

I then tried to google where the power should be coming to that connector and maybe it's this connector and PIN #1? I measured and there's constant 12 volts when car is running. With or without AC on. Dunno if that's correct?

And finally things that Lexia shows me realted to AC. Dunno what to make out of these

Any help would be highly appreciated how to continue finding out what prevents the AC from turning on!

[mickthemaverick]

With the car turned off, have you tried connecting 12V across the terminal of the a/c clutch to see if it clicks in?

[xantia_v6]

Looking at the diagbox picture, I am not sure if the "Compressor authorisation output control" is a positive or negative signal (does "active" mean that the compressor is activated, or that the activation is not authorised?

In the engine ECU (or possibly the BSI) there should be a live data parameter which shows whether the A/C is authorised, you should also check that.

If the above all seem OK, then it is possible that the A/C compressor control circuit in the engine fuse box is faulty.

[mickthemaverick]

Looking at the diagbox picture, I am not sure if the "Compressor authorisation output control" is a positive or negative signal (does "active" mean that the compressor is activated, or that the activation is not authorised?

I take that to mean that it has activated the output to the compressor clutch and hence suggested checking the operation of the clutch with an outside supply. To me this looks like a clutch magnet coil failure, reasonably common problem on these.

[ozvtr]

I unplugged the connector on the right and there was no power between those two pins. I think there should be 12 volts when AC is turned on that would engage the compressor's magnetic clutch?

Yes.
However you shouldn't have 12V on pin 1 of that grey connector, at the BSM, all the time. Yes, that should be the compressor clutch power pin and pin 5 is ground. I would recheck your findings. It's difficult to reconcile there being 12V there all the time AND there being no power at the compressor. That would indicate two faults, and that's unlikely. Possible, but unlikely.

[d-iivil]

I unplugged the connector on the right and there was no power between those two pins. I think there should be 12 volts when AC is turned on that would engage the compressor's magnetic clutch?

Yes.
However you shouldn't have 12V on pin 1 of that grey connector, at the BSM, all the time. Yes, that should be the compressor clutch power pin and pin 5 is ground. I would recheck your findings. It's difficult to reconcile there being 12V there all the time AND there being no power at the compressor. That would indicate two faults, and that's unlikely. Possible, but unlikely.

Thanks for the verification on these. I am sure there was 0 volts on the compressor's connector and also sure there is 12 volts on the pin 1 on that grey connector even with AC off. Only thing that happens is when AC is turned on, the engine RPM slightly increases and voltage on that pin 1 is close to 14 volts. With AC off it's pretty close to 12 volts.

Pins 2 and 5 seems to be connected to ground on that grey connector based on what multimeter tells me.

[d-iivil]

With the car turned off, have you tried connecting 12V across the terminal of the a/c clutch to see if it clicks in?

I haven't tried this yet, but will do! Which color wire on the compressor needs the 12 volts and which one is the ground? I suppose red is 12 volts and green is ground?

[xantia_v6]

Be careful with that test, the compressor clutch coil should have a diode in it, and if you connect voltage the wrong way around, the diode will short, destroying the coil. It is safer just to measure the voltage at the coil.

[d-iivil]

Be careful with that test, the compressor clutch coil should have a diode in it, and if you connect voltage the wrong way around, the diode will short, destroying the coil. It is safer just to measure the voltage at the coil.

Yeah, that's why I asked which wires are which on the compressor Don't want to damage anything more than is already broken.

[xantia_v6]

PSA do not generally specify wire colours, and the colour sometimes isn't consistent even on a single vehhicle. Wires are identified by a code number printed along the insulation every few cm. for the compressor clutch, the positive wire is "8060" and the negative wire is "M802A"

[d-iivil]

PSA do not generally specify wire colours, and the colour sometimes isn't consistent even on a single vehhicle. Wires are identified by a code number printed along the insulation every few cm. for the compressor clutch, the positive wire is "8060" and the negative wire is "M802A"

Ok! Thank you! I'll make sure to look for 8060 for feeding the 12 volts and see if I hear any clicking.

Also based on this diagram from Haynes book, it looks like there's just direct wire from that grey connector's PIN 1 to the compressor clutch? So I could in theory then just replace that wire with new in case the compressor clicks when fed with 12 volts?

[xantia_v6]

Here is an extract from the Citroen wiring diagram (sorry for the poor resolution). The compressor clutch is "8020"and the wires go to the engine bay fuse box (not the BSI as Haynes claim).

[mickthemaverick]

On that diagram Mike the clutch +ve at the fusebox is labelled 5V. Does that mean it runs at 5 volts or is it just unfortunate labelling?

[xantia_v6]

That is a connector designation, 5 pole Green.

See the pages linked from viewtopic.php?p=782862#p782862 for deciphering PSA wiring diagrams.

[mickthemaverick]

Aah, cinq verdi, that's a relief, the concept of a 5 volt clutch wasn't sitting well with me!!