Auxilliary fan

[inarticulate is]

Gents-

My aux fan isn't turning when the ac is turned on & haven't seen it go on any other times recently, the ac compressor will turn but shuts off after things get hot and speeds get low. My question-How do you get the fan out to test? Ive removed 3 mounting bolts & was hoping it would just tip out, but no. its a 91 318is

[DesktopDave]

I had a heck of a time getting to that fan.  I removed the shroud, radiator & engine fan, unbolted the condensor and leaned it far enough back to pull the fan up into the engine compartment.

If the fan runs on high speed you have a bad resistor or a bad low speed relay (K1 IIRC).  Resistors are cheapish, maybe $30?  It's the long metal cylinder mounted on the fan shroud lower driver's side.  Looks a bit like a cigarette but with wires poking out.  You'll have to solder a new one in if it's bad.

I'd pull the relay and short pins 87 & 30, then short the fanstat on the radiator.  It has three wires.  One is ground, one is high-speed, one is low-speed. Short the ground wire to each in turn to see where your trouble is.

Finally, the aux fan might not turn on at all if the A/C pressure switch detects that the refrigerant pressure is low.

[jscribble]

Test (or replace) the resistor and temperature switch. My resistor is the bosch type (pelican parts has pictures of both styles, and was t shaped and mounted on the fan itself. Look at the pics and it will be clear. Mine was $20, the cig style is $25  If the fan comes on with the ac after changing resistor, fan is good. I'm sure someone else can chime in with resistance values to test it if you have a multimeter.

To test the temperature switch, (once again, someone has meter values?) try holding a lighter under the cylinder sticking out of the side of the radiator on the passenger side. It has 3 wires going to it, but be careful to only heat the metal cylinder. A few seconds should do it, be careful not to melt the wires!  The alternative is getting the engine up past half temp (hard to do on mine) to activate low speed, and almost overheating to activate high speed.

I would swap these two parts, because odds are they are shot, and you would probably want to replace them even if your fan is shot too.

Links to parts: Temp switch (lower temp than stock)   Bosch Resistor (T shaped)   Magna resistor (cig shaped)

[inarticulate is]

Thanks I'll check those. The ac works fine when its cool or on freeway, but aux fan never goes even when compressor is turning. Compressor doesn't turn when ac fails. Will ac turn fan on if temp sensor is bad?

[jscribble]

I had the same symptoms, now halfway fixed. I ordered the resistor on a whim, installed it and now fan comes on when ac is engaged, but not on it's own. The #PN for the temp switch is a lower temp (80/88c) than stock and will kick the fan on earlier for both low and high speeds. A working fan will make your ac much more effective at lower speeds or sitting. Like night and day for me.

If you can access the wiring for the fan, you could jumper 12v to it and test it that way.

[inarticulate is]

Thanks, I heated the temp switch no fan, then tested the wire past the resistor it was getting power with the ac turned on but no spinning so guess its a new fan. I'm hoping somebody can rebuild the old one its $325 for a new one at double o2.

[jscribble]

You could do a puller fan and delete both current fans, if your wiring is good and the rest of your cooling system is in good shape. The volvo two-speed would wire in nicely.