Wiring question 1972 911T

[Dourobot59]

Hi folks,
Working on a 72 911T that PO had in a barn for over 10years.

I am wondering if anyone can tell me what this “Delco Remy” (relay?) located by fuses is for?
See photos.
Also included a photo of the car!

[RWebb]

nice color - what is it?

you'll need to trace the wires for the added relay - one bet is to check the headlights...

[Dourobot59]

Not sure what the colour is.
It started life as Sepia Brown
I will trace the wires and post photos

[Trackrash]

Sometimes, back in the day, guys would add an additional starter relay to fix hard starting. I can't believe someone would do it to a 911, but who knows?

I can't see what wires are connected. But as mentioned headlights may be correct. Since the wiring on the low beam circuits in these cars tended to be inadequate.

[Dourobot59]

Hi folks,
Had some time to follow up on where the wires go from the relay.
I am including some photos too.
Upper fuse box position #3 on this car was not being used because this car does not have power windows.
I am thinking about removing it completely to see if it affects anything (highbeam headlight flip?).
Thanks
Larry

[E Sully]

I would definitely remove it.
Hard to tell what it was installed for. Have you checked to see if the electrical systems work?

[cmcfaul]

Don't remove it.
I believe it is for the high beams. Without it, the Hi beam current goes through the turn signal switch by the steering wheel and burns it out. They are (at least were) stupidly expensive to replace and burn out all the time. The relay, while clearly aftermarket, solves the issue.

Chris
73 E

[E Sully]

It would be best to replace it if being used for headlights. Install the JWEST kit
https://www.pelicanparts.com/More_Info/JWSTERLYHLPR.htm?pn=JWST-ERLY-HLPR&bt=Y&fs=0&SVSVSI=5878

[Quickstep192]

My guess is that it may have been for fog lights.



Based on your pictures, it looks like the relay has power coming in from various sources on the fuse panel, but it doesn't look like there are any switch connections or any downstream devices connected. Since you have it well documented, if it were me, I'd disconnect it and see if you discover anything that has stopped working.

[HarryD]

Makes no sense.

As currently wired do the lights and window lifts work ok?

Does the relay click when the windows or lights are operated in any fashion?

Fuse 3 (lower) and Fuse 6 (lower) are connected across the coil of the relay. both are powered by lights and would have no current flow and the relay will not go to the closed position.

Fuse 3 (upper) is connected to the window lift motor and is only energized when the windows are operated. The other side of the relay switch is not connected to anything.

I would label and disconnect the wires, insulate them (as they are all hot) and verify that all my electricals work properly.

[donporfi]

I think, you need first to identify the different contacts of the relay.
Which one is the:
Power or battery +
Power output
Signal for the coil
ground of the coil, or power to the coil and ground to actuate the coil.
With this info you can trace where the power output goes or what it switches.

With the info you are giving I am assuming that
I signal to actuate the coil
II is Battery +
III do not know
and I do not see a ground for the coil .

If this relay has a function in your car wiring and you are keeping this relay.
I would suggest to mount this relay in a more permanent way, it is held by wire ties . And use different colors and wire sizes for the relay contacts.If possible use the Porsche color coding.

[kltarga72]

As Quickstep192 suggested it may be for fog lights
I added fog lights to my 1972 T around the early 70's and had to use a relay to protect the fog light switch. I copied what other P-car owners did and we used a similar relay that you have.
I see where you do not have fog lights. Is that front spoiler fiberglass? Maybe the spoiler was added later and fog lights were not reinstalled.

[Quickstep192]

For some reason, I can’t get this post out of my head.

I can’t see where this relay performs any function since there’s nothing connected to it other than power. If it were mine, I’d remove all of it and if something stops working, re-do it and re-do it right.

[E Sully]

This is not a wiring circuit I would keep. Remove it, and I highly recommend installing the headlight relay kit I mentioned above to protect the contacts in the steering wheel left stalk. You will have to check how original your cars wiring is.

It looks like positions 1 and 3 are to activate the relay coil, closing the contacts across terminal 2 and the unconnected terminal. Normally the the relay coil is connected to 12v and ground to energize the coil and close the contacts. In this case they are connected to lower fuse block 3, power to activate the headlights, and 6, power to activate the right side marker lights.
Now in this situation, when pulling the headlight switch out 1 notch, power would be supplied to the marker lights, and seem to make a circuit through the low beam headlight bulbs to ground. When the headlight switch is pulled out to the second position, both wires to coil terminals 1 and 3 would be 12v. This would deactivate the coil, opening the contacts.
While the coil might activate and close the contacts, this leaves the 12v from upper fuse 3 with no connection. Whatever was being powered seems to no longer be connected.

Just a note, when looking at fuse block connections shown in the wiring diagram, they are actually mirror image of the actual wiring in the cars.

[Dourobot59]

Ok, so the removal is completed.
All the signal lights, high beams, low beams work without the relay in the car.
This car must have had fog lights at some point in the past. There are extra wires wrapped up behind the headlight buckets.
The bumpers were changed by a previous owner back around 1990.
I plan on installing a relay for the headlights this winter.
All the rest of the wiring works in this car.
Somebody asked if the power windows work....this car has manual windows.

I really appreciate all the posts from folks that helped me figure this out.
I am learning so much about this car and looking forward to putting some miles on it.

Take care,
Larry

[HarryD]

Larry,

If you can read a wiring diagram, you can wire it up from this schematic.
Note) the fuse positions are for my 1973. Verify yours are the same (they should be).



Be aware that most of the kits offered are for 1974+ 911's.

I got my parts (relays and new lamp sockets) from Daniel Stern (Daniel Stern Lighting Consultancy and Supply).