924Board.org

rkn · Joined: 01 Apr 2007 Posts: 176 Location: Copenhagen

Happy Tuesday all,
I am trying to wire up my rear wiper. I have a switch in the cabin & two wires going through to the hatch - One has constant 12V, the other has 12V activated by the switch. Now the question is which goes where on the 3-contact plug on the wiper... One contact is clearly ground, one contact goes trough a diode, and one just disappears into the motor. I would just test this by trial & error, but Haynes specifically states that if you switch the two 12v, the diode will blow.

So does someone know exactly what goes to A, B, C below?
(pic stolen from a rennlist posting by 'Izzy')

Thanks! Rasmus

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1980 924NA ROW

Ozzie · Posted: Tue Feb 10, 2009 8:42 pm Post subject:

A BROWN
B GREEN / BLACK
C GREEN
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

Rich H · Posted: Tue Feb 10, 2009 8:59 pm Post subject:

Get it wrong and it'll blow the diode pack

_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

rkn · Joined: 01 Apr 2007 Posts: 176 Location: Copenhagen

RC · Joined: 25 Mar 2007 Posts: 2637 Location: Australia

rkn · Joined: 01 Apr 2007 Posts: 176 Location: Copenhagen

Rich H · Posted: Wed Feb 11, 2009 12:50 am Post subject:

Will take 2 mins if I had a wiring diagram, but I don't....
I'll look later if I get the chance.
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

Ozzie · Posted: Wed Feb 11, 2009 7:42 am Post subject:

Brown is earth.
this is the only one that is serious about not getting wrong.

The other two cause the motor to park itself or run.
If you mix these two it will run constantly. no problem just swap back.

When I got the car back from the windscrren resealers who done my rear hatch the wiring was wrong.
Just blew a fuse, rewired and works fine. Didnt blow any diode.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

rkn · Joined: 01 Apr 2007 Posts: 176 Location: Copenhagen

thanks ozzie, thats reassuring. It does sound strange that something could blow just by switching 2 wires that essentially provide the same 12v...
Haynes says that it will blow the first time you switch it OFF, which sounds strange, but I assumed it had something to do with the current somehow running the wrong way through the diode.
_________________
1980 924NA ROW

D Hook · Joined: 02 Nov 2002 Posts: 3158 Location: Omaha, NE

Do you have this running through a relay anywhere? I'm just asking because I have the wiring harness for the wiper but not sure if it needs to go through a relay.
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'80 924 n/a SOLD

Ozzie · Posted: Thu Feb 12, 2009 8:48 am Post subject:

I have never messd with the original wiring for this so cant say. AFAIK there is no relay.

To find out which wire was which I used a multimeter. Brown went to the terminal that was zero ohms to the body of the wiper motor.
For the other two I connected the constant 12V to make the motor move and then connected it to the other to make it 'park'
I then fitted the remaining wire.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

Ozzie · Posted: Thu Feb 12, 2009 9:41 am Post subject:

Page 273 in the Haynes shows the wiring diagram for the rear wiper.

Cannot see any 'diode'.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

gohim · Joined: 02 Nov 2002 Posts: 4459 Location: Rialto, CA

The plate on the motor where the terminals come out should have numbers stamped or printed on it. Look closely with a strong light.

#31 Goes to the brown wire and runs to ground.

#53a Goes to the green wire running to the green wire on terminal #2 on the rear wiper switch. The two green wires have a plug connector running into a black wire which runs to terminal #85 on the horn relay which is jumpered to terminal #30 on the horn relay which then gets power from fuse #9, switched by the ignition switch.

#53 Goes to the black/green wire that runs to terminal #3 on the rear wiper switch.

Terminal #1 on the rear wiper switch is a black wire running to ground.

The diode is not on the circuit diagram because it's inside of the motor assembly casing, and considered to be not a user servicable part.

Ozzie · Posted: Thu Feb 12, 2009 6:45 pm Post subject:

yet they show the thermal cutout inside the motor?
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

RC · Joined: 25 Mar 2007 Posts: 2637 Location: Australia

Curiosity got me here and there is indeed a single diode mounted not inside but merely on the back (front actually) of the motor.

Porsche don`t consider many things user replaceable parts since they want to relieve you of your money and increase their profits. Unless you own shares in Porsche, like Gohim apparently must, a suitable replacement DIODE can be got at any electronics shop for < $1.

Personally couldn`t be bothered looking up a simple wire colour in the manual, but if it was my car would have done so and quickly discovered which blue wire is which.