M coupe radiator fan

[elwesso]

I've had my M coupe for about 5 years now (up to about 67k miles), and other than normal maintenance I think I've developed my first "problem".

Little bit of background, last summer I noticed the radiator fan would run at high speed more than normal. Basically it seemed like if the fan came on, it came on full speed and stayed there until you turned the car off. Didn't seem to matter if the AC was on or not.

My first thought was maybe the car was overheating slightly, even though I got no warning light... So, for about a week of driving last summer (both city and highway), I used my DashCommand app on my phone/wifi OBDII reader to monitor the coolant temps, and coolant temps were steady around 175°F, give or take a couple degrees and oil temps were normal. So at that point I didn't concern myself with it any more.

So far this season I've probably put at least 1k miles on the car and have been daily driving it for a couple weeks now (I have been alternating cars every week), and everything appears to be the same. Yesterday on my way home from work I took a slightly different route that had me doing more stop/go and slow driving, where normally the car does pretty much all highway driving. About a mile from home, I got the yellow coolant light and oil temps were slightly higher than normal. I turned the heat on full blast, and got the car home. When I got home, the fan was not on. I opened up the hood and let it idle for a while with the heat on, and after a few minutes the light went out. I then shut the car off, and then let it idle again with the heat off, and sure enough the coolant light came on and still no fan.

I drove the car to work again today, and had DashCommand running the entire time, and never saw above 175°F on my highway drive. As soon as I pulled into the parking lot, I let it idle for a few minutes and the temp started to creep up to 180°F.

Regardless of the situation, for whatever reason the fan is not coming on. I would expect either the fan itself or a relay. Did a little bit of searching, not a lot of discussion on this topic other than the fan relay/controller seems to be integrated into the fan itself, which makes testing it a little trickier (versus just jumping the relay). Apparently there's a fuse for it behind the glove box.

I will be doing some troubleshooting this weekend, but I'd be interested to hear if anyone has any helpful thoughts to make troubleshooting a little easier?

[StickMon]

Coolant level OK? I got the yellow coolant light once and found I was about 1/2 a cup low.
I routinely drive in stop/go traffic and the water temp gets up to about 195, with the oil temp just a tick past 12 O'clock.
Cruising the water is 176 and the oil's at 11 O'clock.
Not sure at what temp the fan comes on, but it may be over 180.

[angelr]

I had similar issues last year at around 120k and replaced my fan. No issues since, but I can't say if it was the fan motor or the relay, I didn't have the time to diagnose properly and just replaced the assembly.

[elwesso]

So bringing this thread back to life, mainly because I'm going to be getting my coupe out in the next week or so, I need to get this fan fixed. Before I put the car away I took the fan and shroud out. Pretty nice design there, a couple screws you can get at from the top and the fan and shroud pulls right up.

Again, to reiterate, the fan would work intermittently. When it does work, many times it stays on high speed all the time (not really a problem, just noisy and kind of annoying), but sometimes it does not come on at all and the engine can start running hot if you're not moving (at highway speeds though it was never an issue).

For diagnosis, this fan uses some sort of PWM control or something. There's only 3 wires, (2) big wires for power (fan is always energized), and a small wire for what I assume is control. I tried various things to try and see if something was not causing the fan to come on, or if it was the fan was not responding to controls, and I couldn't really deduce anything..... other than logically, if the fan works intermittently, it's more logical to assume that it's the fan itself and the control signal is being sent to it properly.

I cannot swallow spending $620 on a brand new one without at least trying a lower cost option.

I attached a picture of my fan motor that I pulled off after removing the motor from the shroud and the blade from the motor. I started digging around, and found that the same years 7 series (E66) uses the same fan motor (connector and everything). I think there are other models too that use this same fan motor (I believe the X5, perhaps the 5 series, maybe some others).

Anyway, I picked up a nice looking used one from eBay for $150 (https://www.ebay.com/itm/302579757161). Pretty much all the numbers matched up, and the connector looks the same. Based on forum posts here, it doesn't appear that fan motors are a super common failure, so I figured used might be a safe bet. Obviously I don't really care if the shroud or blades are different, I just need the motor.

I will also likely try and disassemble my current motor and see if I can spot anything wrong. Worst case scenario I destroy it and it goes into the garbage.

[gas-can]

http://forum.e46fanatics.com/showthread.php?t=930848 may help.

If you have an oscilloscope, it would be trivial to get a reading on the pwm leg to see if the main computer is ok (be careful).

If you have a sig generator with a powerful enough 12v power source, you could artificially power and control the old fan.

Honestly, the age is right for a replacement. It's a small price to pay for peace of mind.

p.s.: if you do take the old one apart, I'd check for dead solder joints on the controller. That thing must have gone through a lot of heat cycles, which may have caused solder breaks (->intermittent behaviour).

-gc

[StickMon]

Here's some additional info from the WDS:

Electric Fan

Under certain operating conditions, the engine control activates the electric fan at various speeds.

The electric fan is activated by means of a power output stage directly on the fan motor. The motor control unit activates this power output stage by means of a square-wave signal with duty factors (variable pulse width) between 10 and 90 % thus controlling the various speeds of the electric fan. Pulse duty factors less than 5 % and greater than 95 % do not trigger activation but rather they are used for fault detection purposes. The power output stage features its own positive and ground supply.

The fan speed is influenced by the coolant temperature at the radiator outlet and the pressure in the air conditioning system. The fan speed is reduced as the vehicle speed increases.