switched 12v needed for a 964 C2

[eDart]

I am looking for a source of unfused but switched (on with ignition) power. Out of the ignition switch itself would be okay - anyone know an "easy" place to tap into this?

[johnsjmc]

I would probe the fuse box and find a circuit that is switched .If you don,t want it fused connect to the supply side of the fuse you end up using.
Consider what amperage you are drawing and if much more than the circuit you tap , you could add a relay and only use your switched supply to trigger the relay. I would also use an inline fuse to protect the new wiring

[eDart]

Thanks John, That is exactly what I will do.

[911pcars]

Suggest you confirm the desired circuit with its branch circuits can provide sufficient current for your accessory w/o overloading the circuit.

Obtain a circuit diagram, then trace the source path from the desired fuse to ground while noting the loads attached to the branch circuits (e.g. cig. lighter, blower motor, rear window defroster, etc.).

What are you attempting to connect?

Sherwood

[eDart]

Sherwood, i actually need a location with nothing else on it - basically straight from the key. I have all the diagrams etc but was hoping there was a simple way to attach to the key. I have actually just installed a gm e-rod v8 in my 964 and need to hook up the main ignition/keyed source for the system. The constant 12v was easy in the back.

Gavin

[911pcars]

Originally Posted by eDart

Sherwood, i actually need a location with nothing else on it - basically straight from the key. I have all the diagrams etc but was hoping there was a simple way to attach to the key. I have actually just installed a gm e-rod v8 in my 964 and need to hook up the main ignition/keyed source for the system. The constant 12v was easy in the back.

Gavin

Why not just use the factory 12V ignition systems source wire that's already in the engine compartment?

Find the color coded ignition source wire in the factory electrical schematic.

Sherwood

[eDart]

That was actually my original plan but in talking with others who have done this they all say they come off the key itself. I assume it is to insure the gauge of the wire and that other loads comes off of it. Have to admit that, in spite of all the wiring I have done I still worry about getting this right which is why I decided to ask on this forum.

[johnsjmc]

Originally Posted by eDart

That was actually my original plan but in talking with others who have done this they all say they come off the key itself. I assume it is to insure the gauge of the wire and that other loads comes off of it. Have to admit that, in spite of all the wiring I have done I still worry about getting this right which is why I decided to ask on this forum.

Now that I know what you are trying to do. I would also suggest using the original ignition supply wire in the engine compartment.
It does come directly from the key and is already in the loom.

[eDart]

OK I hear you guys. I will do that.

[dad911]

Or use the ignition circuit to switch a relay, if worried about drawing too much current through the ignition switch.

[eDart]

Dad911, That seems like a great, simple idea.

[911pcars]

Originally Posted by dad911

Or use the ignition circuit to switch a relay, if worried about drawing too much current through the ignition switch.

When the expensive Porsche ignition switch fails, it's usually in the start or crank position. Using a separate switch and relay to perform the actual switching to the starter will extend the service life of the ignition switch. FWIW, here's my remote relay mod.

Remote Starter

Sherwood

[eDart]

Hey Guys, just thought I would give you an update on what I did in case anyone else is in a similar situation. The e-rod computer needs to control the fuel pump - it has a "fuel pump out" wire, so I hooked that up and used the 964 fuel pump power as a switched source for the e-rod computer.

[Don Nguyen]

I am looking for a similar answer/solution to a 12v switched power source in the engine bay. I am not exactly sure where the fuel pump switched source is in the rear. Does anyone have any ideas/suggestions?

Thanks!

[3rd_gear_Ted]

Here is what I mounted in my car.

20 amp in line fuse on main input post

when you track your car, you find needs lots of 12 vdc stuff.
Helmet blower
ECU
Cool Suit
On board transponder
fused portable air compressor 12 vdc source for pit adjustments
Comm



230896

[Don Nguyen]

Originally Posted by 3rd_gear_Ted

Here is what I mounted in my car.

20 amp in line fuse on main input post

when you track your car, you find needs lots of 12 vdc stuff.
Helmet blower
ECU
Cool Suit
On board transponder
fused portable air compressor 12 vdc source for pit adjustments
Comm



230896

That'll be useful to use, but only once after I figure out which wire is the 12v switched wire to connect to! Haha.

[timmy2]

Don, what year is your car?

[Don Nguyen]

My car is a 92 C4.

I've been trying to read the service manuals, but either I am not able to find the correct page or also very possible that I just don't know how to read the wiring diagrams that well.

[timmy2]

Too new for me, my manuals stop before 1990. ...