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Posted by: ClayPerrine Nov 18 2004, 09:02 AM

NOTE: DUE TO MY NOT LOOKING AT THE WIRING DIAGRAM BEFORE POSTING THIS, I HAVE EDITED IT TO REFLECT REALITY!!

I noticed that there is a lot of questions out there relating to how the headlight motors work. So I put this together to see if I can clear it up.

The headlight motor circuit functions like a 3 way light switch in your house. You all have seen them. The one you can turn on at the bottom of the stairs and turn off at the top. Well, when you turn on the headlights in a 914, you turn on the headlight motor. It's rotation turns off the headlight motor when the lights are up, using a set of wiper contacts in the motor.

In the first diagram below, I outline the headlight circuit with the lights in the down position.


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Posted by: ClayPerrine Nov 18 2004, 09:10 AM

In the next picture we see the headlight circuit while the motor is running to raise the headlights.

The headlight switch has connected to the on contact, supplying power to the "closed when down" wiper contact on the headlight motor. The common connection from the wiper contacts then supplies power to the relay to energize it. This connects pin 87 to pin 30 providing power to the headlight motor and starting it running.


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Posted by: Root_Werks Nov 18 2004, 09:11 AM

Cool!

Posted by: ClayPerrine Nov 18 2004, 09:13 AM

When the headlights are all the way up, the wiper contacts in the motor change position, and the pin "Closed when headlight is up" is connected to the common contact. This removes power to the relay coil, and that breaks the circuit to the headlight motor, and the headlight stops moving.


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Posted by: ClayPerrine Nov 18 2004, 09:17 AM

Now we turn the headlights off. The headlight switch connects power to the off contact, and that supplies power to the "closed when up" wiper contact, which then feeds power through the common contact to the relay coil. The relay energizes, connecting pin 87 to pin 30. That supplies power to the headlight motor to make it start moving down.

When the headlight reaches the down position, the wiper contacts connect the common pin to the "closed when down" connection, breaking the circuit to the relay coil, and that turns off the power to the motor.


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Posted by: ClayPerrine Nov 18 2004, 09:18 AM

I hope that clears up the mystery of how the headlight motor circuit works.

Posted by: mikerose Nov 18 2004, 09:27 AM

Thanks Clay

Posted by: dralf Nov 18 2004, 09:34 AM

Thanks,

At the moment I am not having problems, but with a 914 it is just a matter of time and this is wonderful....I am printing it out and putting it in my note book.

Posted by: ppickerell Nov 18 2004, 09:46 AM

Wow, you should try out for admin!

Posted by: jfort Nov 18 2004, 11:02 AM

this needs to go in Classics or whatever it is -- the place for reference material. great job!

Posted by: ClayPerrine Nov 18 2004, 12:51 PM

Bump... updated to reflect the reality of the wiring diagrams.

Sometimes it pays to look at the diagram FIRST!

Posted by: Gint Nov 18 2004, 12:52 PM

Nice work Clay. Many thanks.

Posted by: chunger Nov 18 2004, 03:17 PM

Sweet!

I was thinking about using an aftermarket harness (painless) for V8 car, but couldn't figure out how to do the popups. With this info, I can make the right circuit from scratch.

-'Chung

Posted by: Dave_Darling Nov 18 2004, 05:38 PM

...Is it just me, or are all three of those diagrams completely identical?

BTW, this definitely should go into the "classic" section--it's something that needs to be around for people to refer to in the future!!!

--DD

Posted by: swood Nov 18 2004, 07:05 PM

Great info! My lights go up and down and the high beams come on, but the low beams do not.

Posted by: Dave_Darling Nov 18 2004, 07:10 PM

There is one fuse for each low beam element--two total. (Plus two more for the two high beams.) Check those.

I'd suspect the high/low beam relay, sitting up on top of the fuse panel. I believe that is the last place that both of the low beams share a common signal.

Oh, if your lights are "stuck" on high beam, then I would also suspect the high/low switch in the turn signal switch assembly.

--DD

Posted by: type47fan Nov 18 2004, 07:29 PM

Dave, it's just you! Check the differences in the relay terminals 30, 85, headlight switch, on/off etc. . . .

Wayne (type47fan)

Posted by: 1973TwoLiter914 Apr 29 2020, 02:08 PM

Clay - great visual ! I'm having issue with headlight synchronization and hoping your diagram and perhaps a reply could help me sort out the details...

- Both headlights Hi/Lo work, however it's a 1 Up and 1 Down situation

- Left headlight operates perfectly in relation to the switch.....when switch is pulled out the headlight turns on and flips UP just fine.

- Right headlight operates in the 'opposite' manner - meaning it is UP with the switch OFF and turns on and flips DOWN when the switch is pulled.......leading to a head scratcher.

I've pulled the relay on the RIGHT light and tried to cycle thru with no result......wondering if the wires to the RT motor are somehow not lining up with the proper pins ???

Any help would be great !

Posted by: ClayPerrine Apr 30 2020, 12:15 AM

QUOTE(1973TwoLiter914 @ Apr 29 2020, 03:08 PM)

Posted by: partwerks Sep 30 2021, 06:46 PM

QUOTE(ClayPerrine @ Apr 29 2020, 10:15 PM)

QUOTE(1973TwoLiter914 @ Apr 29 2020, 03:08 PM)

Clay - great visual ! I'm having issue with headlight synchronization and hoping your diagram and perhaps a reply could help me sort out the details...

- Both headlights Hi/Lo work, however it's a 1 Up and 1 Down situation

- Left headlight operates perfectly in relation to the switch.....when switch is pulled out the headlight turns on and flips UP just fine.

- Right headlight operates in the 'opposite' manner - meaning it is UP with the switch OFF and turns on and flips DOWN when the switch is pulled.......leading to a head scratcher.

I've pulled the relay on the RIGHT light and tried to cycle thru with no result......wondering if the wires to the RT motor are somehow not lining up with the proper pins ???

Any help would be great !

There is a connector near the headlight motor with 3 wires in it that hooks the motor to the wire harness. Check it on the side that is working backwards, and verify the wire colors match from one side of the connector to the other.

Clay

Posted by: ClayPerrine Oct 2 2021, 11:02 AM

In the last paragraph. Is that something that could have accidentally been changed on both sides, that would make my lights go down when the switch is pulled out?
Picture of it would be nice.

Also, is there a diagram of the wires that go to the headlight switch, and colors. It's on a 1975.
[/quote]

If the wires on the plugs between the headlight motors and the harness is hooked up wrong, the light will go down when the switch is turned on.

I don't have a 75 wiring diagram. The bird board used to have them up on it, but Porsche got pissy and made them take it down. You can go to the wayback machine and find them there.


Clay

Posted by: iankarr Oct 2 2021, 12:24 PM

This may help…fwiw…I ended up wiring mine backwards…down was up and vice versa
https://youtu.be/lx5tKgLG-_k

Posted by: partwerks Oct 2 2021, 04:03 PM

[quote name='ClayPerrine' date='Oct 2 2021, 09:02 AM' post='2949812']
In the last paragraph. Is that something that could have accidentally been changed on both sides, that would make my lights go down when the switch is pulled out?
Picture of it would be nice.

Also, is there a diagram of the wires that go to the headlight switch, and colors. It's on a 1975.
[/quote]

If the wires on the plugs between the headlight motors and the harness is hooked up wrong, the light will go down when the switch is turned on.

I don't have a 75 wiring diagram. The bird board used to have them up on it, but Porsche got pissy and made them take it down. You can go to the wayback machine and find them there.


Clay
[/quote]

Long story short, the wires in that plastic clip, somehow, somewhere, someone, got them flip flopped. Lights now work, but having trouble with the left turn signals not working, and wipers not working, and hazards are 1/2 as bright?

Odd thing is that I had gotten them wrinkles out from the previous X mechanic that had things all botched up. I mean like putting a foglight switch in place of a headlight switch. But the person I got it from, sent the wrong one, and I had sent it directly to him. Not sure what model it was.

Also, didn't the 75-76 have a 3rd speed wiper, and the relay mounted on the DS cowl support? If so, that never got hooked back up, and I'm not so sure I don't have the correct wiper switch. I think my X mechanic got one that doesn't have that part where you push the lever down to activate it.

Is there a diagram with colors and numbers that I could get for the headlight switch, and the 3rd speed wiper delay for a 1975?

Posted by: ClayPerrine Oct 2 2021, 06:32 PM

All 914-4s had a 2 speed wiper. There was an optional delay relay that could be added. I have the relay and the harness to go in Betty's car when I put it back together.

Clay