 1997 318i M44 Electric Fan Works, But Not Working in Car
Hello,
I have read lots of forums about this here and elsewhere. Lots of great information I have taken to heart, but my symptoms do not quite match those of anyone else I have seen, and now I'm stuck. Quick reminder that I am talking about an M44 engine in a 4-door 1997 318i sedan, so I think this is the same as the 318ti, but there could be slight differences.
My car started overheating once after driving it around a bit and then stopping to let it idle. I managed to repeat that later, where the car did not overheat after a lot of driving around and even idling at traffic lights, but then it overheats once I let it idle in my garage. I haven't gotten it to happen again lately, maybe because it's too cold, but I also cannot get my fan to run.
I've yet to see my fan run in the car on low speed. I thought it started at high speed - and then stopped - once when I turned the AC on, but now I can't get high speed to come on at all, even with the AC on.
This all started after changing out my oil filter housing gasket, so I thought I may have broken something else. But I doubt it - probably more likely I just never noticed my fan doesn't come on.
Connector near radiator: ~12V at BOTH low speed to ground and high speed to ground.
- When I jump HS to ground, the fan runs at high speed. When I jump low speed to ground, nothing happens.
High Speed Relay: Voltage at terminal 30 to ground AND at terminal 86 to ground.
-I have replaced the high speed relay with a new OEM replacement. No change.
Low Speed Relay: Voltage at terminal 30 to ground and NO VOLTAGE at 86 to ground. I switched the relay with the identical one beside it because it's too easy not to try - no change.
5A, 30A, and 40A fuses all good. I took out the 40, and nothing works. Just tried that because the 40 was under the dash, but not exactly where I expected in the auxiliary relay tray.
Took the fan off the car, and wired directly to battery, I can make low and high speeds come on. I still don't know where that resistor is on the fan, but if it's within the fan unit and the three wires that come off of the fan unit, then it is working fine, because the fan works directly to battery on both low and high speeds. IF the resistor is somewhere else in the wiring of the car, then it could still be a problem.
So...any other guesses? If it's the computer, how do I bypass it, or diagnose that? Will a BMW-specific scan tool allow me to change this behavior? Could it be another problem, such as wiring someplace? I did read the Bentley manual numerous times. Slept on it numerous days. Just nothing else coming to me. I mean, if the fan doesn't come on with the AC, I definitely have a problem, right? | 
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