Fwd: <E28>Another heater blower wiring problem!

[Pearson-Franks Family <pearsonf@xxxxxxxxxxxxxxx>]

Darren:

When you say you checked the fuse, which one did you check?  You
refer to getting no juice to the fuse block, which suggests you
might be looking at the little 2-fuse block that gets crusted on
when a/c is added after the car is manufactured (all of the US
ones maybe?).

Anyway, the blower motor is powered off fuse #14, and the rear
defroster is powered off fuse #13, so I would not assume that the
two symptoms have a common cause.  Fuse #13 also powers the
sunroof, so check that out.

If fuse #14 is OK, I don't have a bunch more ideas there.

On the rear defroster:  you can check for power to pin #15 on
the connector to the defroster switch, after you have carefully
pried the switch out of the plastic bezel that surrounds the OBC
and two switches.  It might be more 'proper' to remove the bezel,
but that is best done by first removing the steering wheel, then
the instrument cluster, then the . . . . . you get the idea.  I
use a very small (1.5mm) straight screwdriver to get one end of
the switch up a bit, then ease it further with a medium (3mm)
screwdriver.  Make sure you feed the connector out of the hole
before you disengage it from the back of the switch - you don't
want it dodging back into the hole!  By the way; the pin numbers
are on the back of the switch - you have to figure out where they
hit on the connector - not hard.

Anyway, if you find power at pin #15, then check for a low
resistance (<2 ohms) from pin 'S' to ground - this is the rear
window element itself.  If the resistance is high, the next
place to check is where the wire exits the body and contacts
the window itself.  These contact corrode and 'open up'.  The
best fix is to remove the back seats, remove the rear deck
cover (and speakers), exposing the wires and contacts.

You will see that the contacts are just jammed into the rubber
surround of the window, pressed against the metal plated on the
inside at each end of the window, which in turn picks up all the
small traces across the window proper.  You can slide the contact
out, buff up the contact and the trace on the window (I use a
pencil eraser) and reassemble.  If you are desperate (and short of
time!) you can try gripping the connector in place with needle
nose pliers (without removing anything) and pull the contact in
and out a 1/16", hoping it scrapes it's way through the corrosion.

If the resistance of the element was OK, the switch itself can
also fail.  Look for near zero resistance between pins 15 and 'S'
with the switch depressed.  The switch can be disassembled and
the contacts cleaned, if need be.

Anywho, have fun through all this!  Larry F.

PS:  The fuse numbers and pin numbers are from the ETM for my
      '86 535i - close, but not identical to your 533i.  Should
      not be a problem, but . . .

>Date: Tue, 15 Feb 2000 01:28:16 -0600
>From: "Darren Hamm" <hammd@domain.elided>
>Subject: Another heater blower wiring problem!
>
>Hello All,
>
>A few weeks ago I posted my problem with the heater blower in my 84 533i.
>It doesn't work.  I got many useful suggestions and I thank you for them
>all.  The problem however still remains unsolved.  The blower motor is free
>to move.  I naturally first checked the fuse when attempting to diagnose the
>problem.  The fuse is unbroken.  Later when I went to repair the blower I
>found, using my voltage meter , that there is no juice into the fuse block.
>This explains why neither the heater blower circuit or the rear window
>defroster works, as they are fed by a common source.  My question is what
>should I look for to fix this problem.  I have a chilton manual with a
>"wiring diagram" but it is pretty worthless.  Can anybody suggest a source
>for a quality wiring diagram?  I am assuming that blower is powered off the
>key "run" mode, so I don't want to make my own jumper (very tacky) to the
>battery.  Are there any other fusible links or fuses I should check?  Will
>It hurt any electronics in the car if I temporarily run a jumper wire from
>the battery to the blower fuse?
>
>Thanks
>Darren

- -- 

Pearson-Franks Family
Issaquah, Washington

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