[no subject]

- -The box only contains solenoids and diodes.
- -The clicking you hear indicates that the solenoid that energizes the
motor is working. But there is another solenoid, which inverts the
polarity so the motors turn the other way when necessary. The circuit
for this second solenoid was busted (the copper strip on the PCB was
blown).
- -The circuit blew because of a couple of faulty diodes. These diodes
prevent reverse polarities when the circuits are activated. That is, if
the diode goes, when you press a seat button, you create a short
circuit, which will burn the copper circuit on the board.
- -The box can be blown if it is connected with the power main leads
reversed, and also if the control wires that come from the switch are
not powered just right (positives and negatives through the right wires
and at the right time). How this can happen is not so obvious. It could
just be component failure. In my case, I found mice excrement under the
center console and some gnawed wires; these wires had touched ground and
shorted the diodes. 

The repair is fairly simple if you are handy with electronics and
soldering, but you do have to dismount the seat, which is never fun. 

BTW, the box of the passenger seat in my car has gone again, and this
time I can't find any obvious culprit. 

Hope this helps,

David Morales
Nashville, TN
'85 318i
'85 535i
'87 Alfa Milano

> -----Original Message-----
> Date: Wed, 16 Jan 2002 22:34:47 -0800
> From: Persi Kanga <pkanga@domain.elided>
> Subject: <E28> 535is power seat non-operational
> 
> Just bought a 1987 535is - very nice car.  The controls that move the
> passenger seat backward and tilt the seat back are not working - I
know
> the contacts are okay as I can hear the solenoid box clicking away
when
> the buttons are depressed...the motor just does not kick in.  The seat
> does move forward and tilt up..just not the other way(s).  So I know
> that the motors themselves work, I know that the buttons next to the
> seats are making the contacts and I can hear the solenoids in the
sealed
> box under the seats 'click' when I depress the buttons.  I checked all
> the connections under the seat and they are fine.  Has anyone heard of
> the solenoid boxes going bad (the ones that are mounted under the
> seats)?  Thanks, Persi
> 
> ------------------------------

------------------------------