Aircon pump not getting power

lholman · Post by **lholman** » Tue Aug 27, 2019 2:53 pm

Just got the keys to an '06 Z4 2.5 - Aircon not working. Suspected no gas or faulty pump - Have just had re-gassing company on the phone telling me that the aircon pump is not getting power and that they can't fix - possibly a relay issue? and that I'd need to take to an auto-electrician or BMW dealer. Has anyone had similar problems / issues in the past that might give me a clue? TIA!

ph001 · Post by **ph001** » Tue Aug 27, 2019 3:58 pm

Might be the rad fan that is not working that is stopping the compressor kicking in.

Take the plastic cover over the radiator off. Look at the power connector for the fan, two thick wires and one thin green one. Could well be the green one has disintegrated (even though it looks ok from the outside).

: radiator thin green wire.png (482.33 KiB) Viewed 1108 times

Matty_Z4 · Post by **Matty_Z4** » Tue Aug 27, 2019 8:21 pm

Don't they have a low pressure switch to stop the compressor kicking in when its low on gas?

Did you just speak to the AC company or did they try and re-gas it and it was ok/holding charge?

lholman · Post by **lholman** » Wed Aug 28, 2019 10:34 am

thanks very much for the info on the wiring! regarding the A/C company, they regassed then found pump not working. Assumed it would need a new pump and I ok'd that work - but they then contacted me saying that there was no power getting to the pump and that a fix wd need BMW dealer or auto-electrician. so I've picked the car up again.

ph001 · Post by **ph001** » Wed Aug 28, 2019 11:16 am

I'd like to place a small bet on the original pump being OK. The copper inside the green wire literally turns to dust as it's very thin and water gets in at the connector end. The wire reports the fan speed back to the ECU. No wire = no fan = no aircon pump engagement.

If you have INPA you can test the radiator fan very easily which will confirm if green wire OK. Otherwise you just have to strip the insulation back and inspect.

Tekoo · Post by **Tekoo** » Fri Nov 01, 2019 1:32 pm

What’s an AC pump? Are you referring to the compressor?
How is the compressor on/off operation linked electrically to the fan? Do you have a wiring diagram that confirms this connection?

ph001 · Post by **ph001** » Fri Nov 01, 2019 2:41 pm

The aircon compressor won’t start if the ecu cannot determine radiator fan speed (via the thin green wire).

dwoodford1987 · Post by **dwoodford1987** » Wed Dec 11, 2019 3:41 pm

ph001 wrote: ↑Fri Nov 01, 2019 2:41 pm The aircon compressor won’t start if the ecu cannot determine radiator fan speed (via the thin green wire).

Now dont quote me exactly but i had the thin green wire problem (which is now fxed) and the air con compressor worked absolutely fine even though the fan didnt kick in so i dont believe the two are related. The ECU probably tells the fan to turn on when the AC is turned on but it doesnt (or in my case) didnt know the fan wasnt on as the AC compressor worked fine with or without the fan running.

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