What now.. Aux fan maybe?

[ScottyWM]

Drove home from work today with the AC on 'cause I had to pick up my daughter and she doesn't like the wind blowing on her. Idled for like 10 -15 minutes at the school waiting. Then heard the chime "coolant temp" message. Sure enough the coolant temp indicator was closing in on the red.

Turned off the AC and once we started moving the temp gradually went down to normal.

I just re-did most all the cooling system - radiator, hoses, thermostat, water pump... last year! I've done the fan clutch too.

WHAT NOW?!?

bummed.... wanted to work on cosmetics, now this. Someone buy me a beer...
Scott

[ryan roopnarine]

if nobody's gonna say anything....sounds like your fan clutch is bad. my car could drive around in the florida summer temps with the ac on, and a bad aux fan resistor, no notable change. how much resistance does the fan give you when cold?


Drove home from work today with the AC on 'cause I had to pick up my daughter and she doesn't like the wind blowing on her. Idled for like 10 -15 minutes at the school waiting. Then heard the chime "coolant temp" message. Sure enough the coolant temp indicator was closing in on the red.

Turned off the AC and once we started moving the temp gradually went down to normal.

I just re-did most all the cooling system - radiator, hoses, thermostat, water pump... last year! I've done the fan clutch too.

WHAT NOW?!?

bummed.... wanted to work on cosmetics, now this. Someone buy me a beer...
Scott

[ScottyWM]

Fan clutch feels about right? It hasn't really cooled fully yet, but when I give it a quick flick it spins about 4-5 fins. Does that sound about normal? No apparant leak in it. It's older than I thought, put it on about 5 years ago.

No coolant loss. Not blocked, since it cooled back down once moving. I'm with you Ryan, sure sounds like the fan clutch.

Any other ideas out there?

[ryan roopnarine]

went out to das car 5 mins ago, ambient temp is around 77 or so, car has been parked for 24 hours. with a quick limp-wristed :D throw, my 22k mile clutch turned no more than -90 degrees from 12 o'clock, ie,..... I selected a fan blade closest to 12' position, gave it an aggressive flick of the wrist, and it didn't go any further than 90 degrees, I'd say about 70 degrees or so.

[ScottyWM]

Sounds similar to mine, 'cept my car is still warm and it's a good 85° and 99.999% humidity with no breeze right now.

[ryan roopnarine]

if you have the bentley, i believe there are instructions in there for shorting out the auxiliary fan so that it runs all of the time (for testing purposes). winfred (i'm certainly not holding him to anything) said that the airflow from the aux fan is quite substantial, which should be enough cooling for you to figure out whether or not the fan is dying.

[ScottyWM]

Yeah it's in there. Will look at it some this weekend (95° and humid they say). How much is a new clutch going for these days?

[billb]

That's where I'd look first, before shelling out the bucks. If I get a spare minute Saturday, I'll be happy to come take a look. Two heads are sometimes better 'n' one in this case...

Bill B.
fellow Apexian

[winfred]

you can turn on the aux fan with the 3 wire plug on the right side of the radiator, just short two of the wires together with the key on, one way the fan turns on high, another way low and the last possible way you can short the 3 wires nothing happens. the fan should run on low with the ac on, if not the resister is most likely dead. check the fuses first

[ScottyWM]

Haven't really had a chance to check out the aux fan or anything yet. Gotta go to work now. I'll try to look at it this weekend. (no big hurry, I can drive my POS truck for a while.)

Thanks everyone. - Bill, I may give you a call if I run into any questions.

[Bill R.]

radiator will have 3 wires that control the low and high speed on the aux fan..
Violet/gray striped jumpered to Brown will run the low speed
Black/gray striped jumpered to brown will run the high speed..

The low speed on the fan draws 11 amps
The high speed draws 30 amps..
The fan always starts on low speed and then switches to high speed
If you try to start it on high speed it will frequently blow the fuse because the amp draw is too great on initial startup to high speed, thats why its usually running on low then switches to high.

The temp switch on the radiator turns low speed on at 91C and high speed at 99C
There is also a high pressure switch on the A/C system that will turn the high speed on when the ac pressure hits 261 psi
the low and high speed relays in the aux fuse box are k21 and k22











Haven't really had a chance to check out the aux fan or anything yet. Gotta go to work now. I'll try to look at it this weekend. (no big hurry, I can drive my POS truck for a while.)

Thanks everyone. - Bill, I may give you a call if I run into any questions.

[mrbmw1]

I just replaced mine on my 94 540i 2 weeks ago luckily i had a spare one from my last car.

[Robin-535im]

Here's what I did. Let the car idle for a while until it starts to get hot. Then stick your hand in the fan - if any fingers get cut off, it's working, which is good because you would have needed those fingers to change it if it were bad...

Ha - really though, car idling at full temp, if the clutch is engaged, when you kill the motor (do it with the hood open so you can see) the fan will stop immediately with the engine. If it spins for a few revs, it wasn't locked up. It disengages pretty quick once you kill the engine so don't expect to be able to tell once the car is off.

This is a cheap test - and it only tells you "Yes, it's working". If it doesn't behave as above, that doesn't mean it isn't working, just that under those conditions it didn't lock up. It might be worth the 10 minutes it takes just to rule it out though.

- Robin

[ScottyWM]

Thanks, since it cooled off when moving it would seem that it'd have to be either the clutch or the aux fan, (not clogged up or bad t-stat / w-pump). Both look pretty simple to diagnose. Let me call BMA and check the price on a clutch....

Could I possibly luck out and have it be a fuse???

[ryan roopnarine]

the shorting procedure mentioned is meant to be a test for whether or not the fan motor is still operational....ie, if you did it, and the fan spun, you could be assured that any fuses that supply the unit are OK, and that the radiator resistor was dead. I drove to nasty miama last july with an ambient temp of 97 or so with a failed resistor, and i also did a bit of driving in the city when i got there. I was concerned about the fact that the fan wouldn't come on with the a/c, but throughout the whole time, my temp did not budge from normal 12'. I doubt that the electric fan is the culprit in your case. a new resistor was about $11 from bma when i ordered it last year, perhaps if you hold off on purchases until you've verified the fan is optional, you can fix both problems at the same time (if the resistor is in fact a problem for you) by buying the clutch and the resistor in one motion.



Thanks, since it cooled off when moving it would seem that it'd have to be either the clutch or the aux fan, (not clogged up or bad t-stat / w-pump). Both look pretty simple to diagnose. Let me call BMA and check the price on a clutch....

Could I possibly luck out and have it be a fuse???

[ScottyWM]

On the Aux fan. Sure is nice when it's something easy and cheap!! Thanks for all the information, I'm sure it'll be useful down the road.

Now to start on the headliner... well, after cutting the grass, painting the windows, cooking dinner...

[winfred]

generally it only blows the fuse when the resister is bad and the fan has to start in high speed, when running in high it draws about 25 amps but starting amp draw in high is about 55 amps for that pig of a fan motor. id check that the fan will run in low speed


On the Aux fan. Sure is nice when it's something easy and cheap!! Thanks for all the information, I'm sure it'll be useful down the road.

Now to start on the headliner... well, after cutting the grass, painting the windows, cooking dinner...

[ScottyWM]

Yeah, checked both speeds, it seems fine. Ran quite a few miles with AC on yesterday to see how it did - no problem. I actually think the fuse may have been blown a long time, as I don't remember hearing that fan run - and it's certainly hard to miss when it kicks in. (rarely use AC)

I'll keep an eye on it though.