What voltage to air con pump

[tonygreen1966]

Hi,
My new Air con pump is not working -clutch not engaging on pulley and no cold air. What voltage should I have going to my air con pump on my 2003 xc90 D5. I'm measuring 3v with a/c switched on and with ignition on and also with engine idling. I've checked vida but can't find any specified voltage.
Not sure if a/c was working before as it's the wife's car and I only changed it after the belt broke and I suspected the a/c pump as the pulley would not turn freely at all.
It's all just been re gassed by kwik fit .(No charge because my a/c not working. They were very helpful)
Cheers
Tony

[Tannaton]

Its a full fat battery voltage supply to power the clutch, rather than a signal, so with the engine running you should be i.r.o. 14 volts.

Make sure that the AC is on (not Eco) and the temp is set to cold and the fan is on full. Check the fuses.

The other thing to check is there is at least one pressure switch in the AC system that will disable power to the compressor if the pressure in the system is low. This is to prevent damage as the gas is also the lubricating oil for the compressor.

[oragex]

Ive heard 3v is fine for the clutch plate electromagnet, from another post. I'll try to measure mine

[tonygreen1966]

Thanks Oragex I appreciate it.

[Tannaton]

Originally Posted by oragex

Ive heard 3v is fine for the clutch plate electromagnet, from another post. I'll try to measure mine

Where do the other 9v go then?

You can test it by running disconnecting the spade terminal and running a wire directly to the +12v battery (or jump start junction on the XC90).

You dont need the engine running, you will be able to see and hear the clutch closing if all is ok.

[oragex]

Updating this, I've measured at the wire right after starting the car (so normally it should be powered to activate the clutch plate) and it was indeed same voltage as the alternator (it can vary between 13.5-14.5v). So if you get only 3v it may mean that the computer wants to cut off the compressor for some reason (normally to protect if if the has pressure is too high or too low).

[tonygreen1966]

Thanks for taking the time to do that Oragex that is very much appreciated.

[tonygreen1966]

Sorry folks I forgot to close this off so doing it now.
Turned out to be fuse for Accelerator pedal sensor (APM), AC compressor, fan electronics box, 10A.(Fuse 11 I think)
The 3V I measured must have been from the diagnostics circuit?

[Fitzy73]

Thanks for this thread, I will check mine as the A/C person working on my car (2014 XC70) couldn’t get it working without powering it directly as it was only reading 2.4 volts.

Fingers crossed!

[Tannaton]

If you're getting 2.4-3.0 volts - it's likely "ghost" voltage if you are using a high impedance digital multimeter. Try lobbing a 5w side light bulb from the wire to ground and then measure the voltage - I bet it's near to zero then.