Aux fan

[MrBurgundy]

This thread probably isn't in the right place, but I need some help. I have a 530i at the shop that was over heating due to the AUX fan not working. I replaced the fan, thermostat, coolant temp sensor check all the fuses and the fan still wont come on. If i plug the old fan in then disconnect it and plug the replacement one, then it will come on for a brief second. After that it will stop, but it will try and spin.

Any help or insight would be much appreciated

[vpilarrt]

There are 2 relays in the fuse box that powers the Aux fan - 1 for the normal (low) speed and 1 for the higk speed. They're operated by the temp sensor when the temps goes above the switching levels. You can simulate this by running a jumper between the 2 appropriate contacts in the harness connector.

Don't know the year of your car but here are the specifics for a '94 530i:
Normal speed relay is K21, temp switch contacts are 1 & 2
High speed relay is K22, temp switch contacts are 1 & 3
Temp switch switches the ground leg
Position 87 on both relays sends the 12V to the respective fan motor leads

[jlevie]

What year 530?

[MrBurgundy]

Sorry its an '03

[Swanny]

We have the same fan! Mine wont turn off though....something to do with the pulse generator or something.

Anyway, check in the hidden ebox under your passenger side intake and look for any blown fuses or relay issues.

I currently have mine routed through a relay thats just an ignition switch. Works for now but that shit is on 747 take off speed.

*edit - 2000 528it that hit the cutoff of a 3 wire aux fan w/o the easily replaceable resistor pack*

[vpilarrt]

An '03 - forget everthing I said. Have you posted on E46fanatics? Probably is similar operationaly.

[jlevie]

An 03 will have a PWM variable speed aux fan controlled by the DME. A DIS/GT-1 has a diagnostic routine that can force the DME to run the run the fan in order to tell if the fan or the DME is the cause of the fan not running.

The aux fan won't be the cause of the engine overheating when A/C is not in use.

[Swanny]

Sorry to thread jack but does the pmw default to a "safety" mode that runs 100% of the time? Thing seriously is at full tilt even with the key off. I believe the signal wire was at 5 ohms resistance and figured that a signal generator would allow me check if i could control the speed of the fan.

Its not a big deal now that i have it switched to my ignition and is my main cooling till i get a new spal for the radiator. It is loud as hell now though

Looks like i might need to invest into an eBay diagnostics kit for my laptop.

[jlevie]

So far as I know the fan does not have a fail safe mode that caused it to run all the time.

[Swanny]

So most likely back to the dme for a fault. Balls.

[jlevie]

Does the fan run when ignition is on, but the engine isn't running? That will be a failure in the controller board in the fan. If the fan only runs when the engine running when it shouldn't be, the DME is sending the PWM signal to cause the fan to run. That could be a bad DME, or it could be a bad temperature sensor/input to the DME. Five minutes with a DIS/GT-1 will tell whats going on.