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Fan blower electrical fault

Posted by rafferox 
August 08, 2011 04:16AM
The warmest hello to the community from France. Still alive, still with my 320ic (11th year toghether!).

So, the small question is about the fan blower that don't want to work surely for some electrical fault (don't work in any position).
All fusibles are in working order. I think is some relay but really too hard to me to understand where is the related relay and which one.
Is there somebody can bring me a light on?
Thanks in advance winking smiley

August 08, 2011 03:52PM
Hi Raffaello, welcome back!

Does your car have power side mirrors, i.e. can you adjust their aim via the switch on the driver's armrest? Are they still working now?
August 09, 2011 06:51AM
Hi Raffaello, welcome back!

Does your car have power side mirrors, i.e. can you adjust their aim via the switch on the driver's armrest? Are they still working now?

Don't all e30 have electric side mirrors?

Do you have the wiring diagrams to trace the connections related to the fan blower?

confused smiley
August 09, 2011 08:44AM
Does your car have power side mirrors, i.e. can you adjust their aim via the switch on the driver's armrest? Are they still working now?
The reason I ask is because the side mirrors draw power from the same source as the blower motor, through the K7 Unloader Relay. If the relay is dead, then the power mirrors won't be working either. But if the mirrors are working okay, then we can eliminate the K7 unloader relay as the cause of the problem.

Detailed wiring diagrams for your model year can be downloaded from here: http://shark.armchair.mb.ca/~dave/BMW/e30/

Find page 0670-0 (Power Distribution Box), it shows the location of the K7 Unloader Relay. It's the one nearest to Fuse-25. The purpose of the unloader relay is to remove power from various unnecessary accessories while you're cranking the starter motor.

Now find page 6413-0 A/C Blower Controls. At the top of the diagram you see that power is supplied to the blower circuit via the K7 Unloader Relay only when the ignition switch is in the RUN position. When in the OFF, ACCESSORY, or START position, no power is provided to the blower circuit. So the K7 relay would be the first thing to check. Try swapping it with any of the other similar relays in the fuse box.

From there, power flows through the 30 amp Fuse-20 (check that!), and down the right side of the page through the Blower Speed Control switch, and depending on which setting is selected from there through the Blower Resistor pack, through the Blower Motor, to ground.

The blower resistor pack is a common source of problems. It will eventually and inevitably rust out and then need to be replaced. It also has a safety switch inside it that limits the amount of current that will flow through it. If the blower motor is drawing too much current, that safety switch will heat up and open. After it cools off, it should reset itself.

As you can see from the wiring diagram, if you select position 4 (the highest fan speed setting), it bypasses the resistor pack altogether and feeds power directly to the blower motor. So regardless of the condition of that resister pack, the blower motor should still run on the highest speed setting, position-4.

If it doesn't, then the problem is with the electrical connections to the blower motor, or more likely the motor itself. The bearings eventually seize up. You can try squirting some light oil into them, but that is a temporary fix at best. The oil will accumulate dust and the bearings will only seize up again even sooner. If the bearings are seizing you would probably either be blowing Fuse-20 or tripping the safety switch inside the blower resistor pack. Then it's best to just get a new blower motor.
August 09, 2011 02:07PM
Thank you for the moment, I forget how efficient quick and precise is this wonderful "must be there"...
First of all I can say that mirrors devices works fine (left and right). Tomorrow morning I'll check all the fusibles (again) and the K7 relay. Only I can't have another right now, but it seem a
You're PRECIOUS...!
August 10, 2011 04:37AM
So the relay K7 "look" ok (I'll say better when I'll replace it with another). Just I've noted that with electrical power in ON position and while blower is on 4 (the faster and bypassed) I can ear a "tic... tac..." sound, intermittent for about 3 second (I mean: "tic-tac, 1,2,3, tic-tac" and so on) coming from the back of the buttons right up the blower unit (hazard, rear window blower etc). It seems there is no way to fix it without opening... ( but my tools are far away 200kms now... sad smiley )
August 10, 2011 09:32AM
If the mirrors are working, then you already know the K7 relay is okay and that's not the problem.

If you press the A/C button, or the Recirc button on the heater control panel and the button lights up, then you also know that Fuse-20 is good and there is power coming through.

It sounds like you will need to have a closer look at the blower motor itself. It's not that difficult. You go in through the engine compartment. There is an access panel on the firewall, behind the engine. A screwdriver should be all you need. Try not to drop the screws though.

Once you get the access panel opened, you'll see the blower fan motor sitting there. It has some shroud covers over the plastic fan blades. Pick whichever one of these diagrams looks most like yours. Remove the shroud covers to see the motor.

Turn the blower fan by hand to see if it spins freely.

You can try unplugging the blower's electrical connecter, then running a couple of wires to the blower motor directly from the car's battery to see if the fan motor runs.

If the bearings are sticky, you can try squirting some light oil into them to free them up. But that is just a temporary repair. If the bearings are sticky you are better off buying a new blower motor.
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