Aux fan works when jumped, changed switch and still nothing

[ghrays]

Don't assume that. Jumping the connector with a wire is different than 30 year old female terminals mating to male terminals. I've bought numerous switches because I assumed that and eventually had to replace those female terminals. I'm guessing they open up over time and fail to make proper contact plus corrode.

This happened to me, the auxiliary fan came on when jumping from the radiator switch but wouldn’t reliably turn on when plugged in and the AC switch turned on. The female water tight terminals on the body harness were too loosely mating with the male connectors on the fan harness plug housing. Cutting out the old terminals and soldering in new finally fixed the issue. It was either 61130007442 or 61130007446 snap in receptacles.

[hozzziii]

Yes that is how it's designed to work. Resistors resist the current that's trying going through the wire and that's why you get low speed cuz there's less current going through.
However in doing so, the do absorb some energy and get hot, and they need to get cool otherwise it could melt and now you have now resistor.
That's why the resistor has these fins on it that help keep it cool. That's fine for the environment it's in, it's just in front of the car, getting airflow. You're good.
Now put it all together and see if you get the fan on with the ac button.

I'm still not convinced it was the resistor though, but let's see if it works.

[snowfox]

reelizmpro hozzziii ok, so new resistor arrived although the wire is a little thinner at 2.5 mm vs the wiring in the car that appears to be 4 mm. I used alligator clips to test the resistor and worked like a charm. However the resistor after maybe 30 seconds of run time was very hot. Is this normal? Can you guys let me know if yours gets very hot?

[hozzziii]

Yeah this doesn't make sense. You were able to get it jump started in both low and high speed.
Like, we know that the low speed relay and resistor should be ok.
My brain is no longer braining.

I had thought about changing out the rating on the wire wound resistor to change my fan speed for my m30 swapped car. I didn't want it to run max speeds all the time because it was too loud and the low speed was not enough to keep my AC cool at stop lights. Factory replacement "Magna" resistor(ACM) is about $20... but about $10 on amazon for a no name brand. The resistor rating is 85w - 0.5 ohm.

If you do change the rating you have to swap the 15A fuse for the low speed too.

[uturn]

I had thought about changing out the rating on the wire wound resistor to change my fan speed for my m30 swapped car. I didn't want it to run max speeds all the time because it was too loud and the low speed was not enough to keep my AC cool at stop lights. Factory replacement "Magna" resistor(ACM) is about $20... but about $10 on amazon for a no name brand. The resistor rating is 85w - 0.5 ohm.

[snowfox]

reelizmpro I’m not able to get a resistance reading on my multimeter.

[reelizmpro]

reelizmpro hozzziii Not sure how this can be, but I cut the low speed resistor out and jumped it (changed the fuse to a 30 amp) and fan kicks on perfectly with the AC button. Who knows...now for the fun part I seem to have a fan by the brand name "power motion" and it has a "power motion" resistor that looks similar to the Magna one, but not identical. I cant seem to find anything by the brand name power motion. Have you ever heard of it? Should the stock resistor work? Thank you so much for the help!!

I've never heard of it. What is the resistance of the resistor?

[snowfox]

reelizmpro hozzziii Not sure how this can be, but I cut the low speed resistor out and jumped it (changed the fuse to a 30 amp) and fan kicks on perfectly with the AC button. Who knows...now for the fun part I seem to have a fan by the brand name "power motion" and it has a "power motion" resistor that looks similar to the Magna one, but not identical. I cant seem to find anything by the brand name power motion. Have you ever heard of it? Should the stock resistor work? Thank you so much for the help!!

[reelizmpro]

The AC switch bypasses the dual temp switch so the connector is not the problem. The relay works since it kicks on when you jump the temp switch. Bypass the diode and see what happens. If the fan kicks on then you know for sure it's a bad diode. If not, then check the connections to the diode.

[snowfox]

hozzziii I pulled the relay and did as you said and its showing I have power. I used the diode testing on the multi meter and it says the diode is good. I am at a loss....maybe it is the female connections.

[hozzziii]

Every relay has these pins or terminals on the bottom.

Those metal things that stick out below are the pins or terminals. In this case there are only 4 pins, 30,85,86,87. Why did they name them like this? I dunno.

This is how 4 pin relays are wired.
Power should always be available through a fuse on pin 30.
Pin 85 is connected to ground, and pin 87 is connected to what you want to drive, but only provides that power when you want it.
Pin 86 is the one you control, should you choose to turn on whatever is connected to pin 87, either a fan or horn or headlight or so on, you provide power to ping 86, and that power just goes through 85 to ground.
However what that also does, is create a magnetic field through a copper coil inside the relay.
And that magnetic field pulls a tab that is directly connected to pin 30, and slaps that tab onto another contact in the relay that comes out to be pin 87, then your fan or headlight or whatever is on.

That's why you here that audible click that a relay is on. Like when you use your turn signal, that audible clicking is the turn signal relay in the cabin.

Now what I mean by checking if you have power at terminal or pin 86 is, the relay has bunch of male pins sticking out the bottom, and they go into the female pins or terminals on wherever this is getting installed, in this case your car's fuse box.
So, you have to figure out which relay we are talking about here, on BMW E30's, the fuse box cover has the locations printed on it.

This is that cover. From the wiring diagrams posted above we know we are looking for the relay that is in the K1 position.
So you take out the relay, due to the arrangement of the terminals, it can only go in one way so it's fine.
Look at the bottom of the relay, the terminal numbers are printed in the plastic, next to each terminal there are numbers 30,85,86,87.
On the fuse box, you have to check for power where pin 86 of the relay goes into, not the relay itself.

And that's how you find terminal 86.

[snowfox]

Hozzziii where is the 86 terminal? Sorry I am totally new to working on electronics.

[hozzziii]

This is from an early production manual car.
I looked at the late production ones as well and with both manual or auto the aux fan relay also gets power from the black/white wire after the evaporator temp switch. Just the auto cars have a kick down relay which is another story.

By the looks of it, if your compressor is working then you have power at the black/white wire, so that's good.

My guess is you should check the black/white before the aux fan low speed relay.


We know the fan can work when you jump the low speed sensor wires, so the fan and low speed relay are good.

And as you can see the low speed relay gets its signal from both the low speed temp switch and the ac circuit. Hence why you need the diode so the low speed switch doesn't turn on the compressor.
Now your issue could be the diode, or a tear on the black/white wire.

I suggest you test for power at the 86 terminal on the fuse box where the low speed relay goes.
So get a multimeter, turn the car on, turn on AC, take the low speed relay out, check for power at the 86 terminal, you can use a strut bolt or the 85 terminal for ground, if you don't have power, then it's either the diode or the black/white wire.

If you do have power, then I'm confused.

[reelizmpro]

ahhh this is about the AC...I misunderstood your post.

Here you go, although a new diode didn't solve his problem at least you have more info.

https://www.r3vlimited.com/board/forum/e30-technical-forums/general-technical/363011-fusebox-diode

[snowfox]

Does the ETM show the part number for the diode? My AC works great, just not when your sitting still which I know is because the fan isn’t working.