Radiator fan not turning on Now a/c compressor issue?

[jmotsch]

Hello. I took my 2003 z4 to a local shop to have the a/c serviced and through the process they discovered and told me my radiator fan was bad and needed replaced. It will not turn on when the a/c is turned on. They stated that they tested that the fan was getting power and felt certain the fan it's self needed replacing.
Knowing this is an easy job I opted to do it my self and ordered a used fan on EBay. Swapped that in and no luck. I checked and I am getting power at the plug. No visible corrosion or issues with the green wire. The a/c compressor clutch is kicking on. I've read several other posts regarding fan issues and I'm just not sure what my next step should be.
Did I buy a bad used fan?
Is there a way to bench test one of these fans?

 

[jmotsch]

An update if anyone has any ideas. I tested that I am getting power to the plug and I ohm tested the green signal wire from the computer to the plug end and I am getting continuity. I returned the used fan and ordered another used fan and the seller assured me it had been tested. I swapped that one in turned on the a/c and nothing. I know it is a coincidence but as I was messing with the air quality sensor mounted on top of this fan, the fan came on for 10 seconds or so and then turned off and wouldn't come back on. Car does not overheat and the a/c isn't blowing very cold. I've seen other forums suggest on similar vehicles that the a/c pressure can affect whether the fan comes on? I've seen this fan run so it seems my issue is somewhere else.

 

[bigwinn]

The green wire is a deceptive one

It may look ok but until you 100% check your continuity I’d not rule it out as it impacts the fan and ac

It’s easy to jump/bridge it across the plug

 

[BumpyZ4]

You may get a good reading with a meter as it does not load the system. If you get a test light (or make one) that has a high wattage bulb that will pull a load on the system you may find that that "voltage" you are reading drops to near zero which will normally indicate a bad ground (corroded or broken strands).

 

[jmotsch]

The green wire is a deceptive one

It may look ok but until you 100% check your continuity I’d not rule it out as it impacts the fan and ac

It’s easy to jump/bridge it across the plug

Can you explain what you mean about jump/bridge across the plug? I'm fairly new to electrical stuff but learning. So far I checked the green wire from end to end but you are saying that isn't enough to determine if it is bad?

 

[jmotsch]

You may get a good reading with a meter as it does not load the system. If you get a test light (or make one) that has a high wattage bulb that will pull a load on the system you may find that that "voltage" you are reading drops to near zero which will normally indicate a bad ground (corroded or broken strands).

I will check this also a bad ground does seems like a possibility. I still need to drive it with this new fan and see if it will turn on when up to temp.

 

[bigwinn]

You can trace the green wire to the top and bottom of the plug (where it corrodes)

Simply cut and bridge the plug to see if that fixes the issue

Your fan should run for 10secs on startup if the ac button is depressed

 

[Pondrew]

It may be of use to know that the fan is controlled by a high pressure switch for the a/c (temp for the rad).
If the coolant temp is not requiring the fan to run, the a/c will cycle it on the HP switch.
If your a/c refrigerant charge is low, the fan will not run as you will not reach the required pressure (around 140psig for R134a).
It could be a faulty HP switch, but unlikely, as something else would give if that were the case.
HTH

 

[jmotsch]

It may be of use to know that the fan is controlled by a high pressure switch for the a/c (temp for the rad).
If the coolant temp is not requiring the fan to run, the a/c will cycle it on the HP switch.
If your a/c refrigerant charge is low, the fan will not run as you will not reach the required pressure (around 140psig for R134a).
It could be a faulty HP switch, but unlikely, as something else would give if that were the case.
HTH

This is is interesting as the original reason I took it to the shop was to service the a/c. Currently the a/c clutch does engage but the air is just cool I wouldn't say cold like a/c should feel. The shop claims this is because the rad fan isn't blowing through the Condenser. Does that sound reasonable or would I expect it to be fairly cold regardless of the rad fan blowing?

 

[jmotsch]

Okay here is the latest. I guess I should not trust a mechanic without double checking for myself. I took the car out for a spirited drive and got it home letting it idle and the radiator fan is on and running just as it should. I went ahead and swapped in my original and it works too! BUT still does not come on with the a/c. So given my a/c Is not blowing cold and the mechanic claims to have serviced it but I'm guessing they just pumped in the freon saw the clutch was engaging and didn't go any further.
I just put my guages on and Its Reading 90psi on the low side and about 110 on the high side which makes me think it's not pumping and probably a bad compressor? Is replacing a compressor terrible.on these cars?