Help! Aux Fan Problem--Bentley Misprint?

[TrentW]

Okay, first of all, I searched on this already. Need to get my a/c working but I'm tackling the aux fan first, as it doesn't come on w/a/c engaged. The damn Bentley manual is confusing me! I tested by jumping at the connector as Bentley shows, and got high speed fan operation but no low speed. When I tried jumping low speed op again, I can hear clicking coming from the fuse box. Figuring it was the low speed relay, I swapped the one from my wife's E30 (it isn't running yet so can't be sure it's good), but still no low speed.

Now, here's the interesting part--I think there may be a misprint in the Bentley. Section 7, page 17, first paragraph. It gives two tests for the fan if running only at low speed and I believe the second sentence should read "If the fan runs only at high speed..." Which probably means I need to check the resistor with an ohmeter? Can someone verify this or tell me what the fix is?

[bmw325csi]

probably the resistor.

[TrentW]

That's kind of what I was thinking, but I'd like to know for sure. First of all, getting to that resistor is no fun. Second, I just checked the resistor on my car (89 325is) and it isn't like the white one shown in Bentley that you can disconnect the wires from and check resistance. It's a Siemens sealed one that you can't disconnect except at the connector. I traced the 2 black wires going into the harness and to a connector behind the headlights, but there's only one black wire, a red and an orange. ???

I remember seeing something about just wiring it so that the high speed fan comes on at the lower temp, but not sure how hard that would be. Maybe easier than replacing the resistor though.

[atldohc]

first checks would probably be to check the resistance of the resistor. if its too high or infinite then the voltage is not gonna get through. if this is the case then just replace it or bypass it. also check voltage before the resistor. if you dont have 12v then youll need to start checking the wiring etc.

[atldohc]

oops u posted before me. well if you cant test the resistor directly you could try connecting a jumper wire before it to right behind it. if fan comes on theres your problem

[TrentW]

oops u posted before me. well if you cant test the resistor directly you could try connecting a jumper wire before it to right behind it. if fan comes on theres your problem

If I could find both ends of the resistor, I'd of course be able to check resistance. Again, the wires going into the resistor are sealed and only one of the black wires from the resistor are visible at the connector on the driver's side when it comes out of the harness.

[TrentW]

Okay--I just poked thru the wiring insulation on both sides of the resistor with my ohmeter and got a 0 reading. Doesn't that mean power should still be going thru the resistor? Bentley says it should read 6 ohms. I'm leaning toward replacing the resistor, but don't want to go thru all that and not be absolutely certain.

I just jumpered the K1 & K6 relays at terminal 87 and pulled the #3 fuse and the fan runs on high with the a/c on. It's really loud though and don't think it's a good idea to run on high for long.

Hep me someone, hep me. It's hot in Chicago now.

[TrentW]

I managed to get my voltage tester into the tight space and poked thru each wire w/key on a/c button on. I only have power to one side of the resistor. Luckily, my tech friend Ben has a new Magna resistor for me. Problem solved--as long as my system holds the R12 it's getting tomorrow.

[TrentW]

Just an FYI--You can replace the resistor without too much trouble thru the front of the car, and not have to mess with removing the radiator and condensor. Remove the kidney and driver's side grilles and cut the wires at both ends as close to the the resistor as possible. Then solder and use heat shrink tubing the lower wire to the new resistor. My Magna resistor mounting screws were rusted too bad to even get a phillips screwdriver in (you can't access the top mounting screw at all), so I ended up using a hose clamp to mount it to the existing resistor. The old resistor also acts as an additional heat sink--the resistor gets quite warm when in operation. Then solder and heat shrink the top wires together and use a nylon zip tie to secure the wires away from the condensor/radiator/resistor and you're done. Here's a photo of the new resistor mounted: