understanding the ignition switch

[SpyderMike]

Used as a power distribution point in my 1985 Carrera 3.2:



Starting at the top going clockwise:

R - 1 medium gauge yellow wire provides power to the radio - it is hot in all key positions except off.

15 - 1 large gauge red/black wire which Ys at a connector and then feeds fuse box 1 fuse 7 in powering several items. Powered in the RUN and START key positions.

50 - 1 large gauge yellow wire to power the starter solenoid. Powered only in the START key position.

P - 1 medium gauge gray wire provide power to the turn signal and headlight dimmer switch in the OFF key switch position only.

30 - 1 large gauge red wire that is the always hot feed from the battery into the switch. This is connected to a smaller gauge yellow/red wire to an inline fuse to the radio and a large red gauge wire to the light switch.

X - 2 large gauge wires - one is red/yellow which goes to fusebox 1 fuse 5 for heating controls and outside mirror circuits. The other is red/white and goes to position 75 on the light switch as the main power for the lights. This is powered with key switch in positions ON and RUN only.

30 - the other large gauge red wire through the bulkhead connector that is the always hot feed from the battery into the switch.

I hope this is useful and has not already been detailed. I apologize in advance if I have made any errors.

[SoCalSK8r]

Very useful, thanks for your contribution.


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[Coastr]

On the topic I now have two ignition switches, one with a 911 part number and one with a 964 part number.

The 911 part doesn't have any ignition lock out (where you have to return the key to vertical before starting again, so you don't try and start an running engine) but the 964 part does.

The 911 ignition lock I have appears to have the ignition lockout on the ignition lock itself.

If I am correct it seems that for the 964 they changed the switch to include the lockout.

[88911coupe]

Awesome, thanks very much for this! Plan to print this and put it in my Bentley manual.

[sugarwood]

How do wires plug into those cavities? Banana plugs?

[SpyderMike]

No. This electrical module plugs into the back of the mechanical switch. The wires extend out the back of the module in the photo. The wires are crimped onto the back side of the female contacts you see. You can physically grab this module from behind and pull it to disconnect it from the mechanical switch.

What is interesting is how easy it would be to hotwire this car. You just need a mating module with switch. Of course the steering wheel would be mechaically locked.

[SpyderMike]

The other thing I am thinking is that the designations of these positions on this module define power buses that are used throughout the schematics. Look at the Bentley or Haynes and where you see the X or the P etc, it appears to relate back to these power feeds.

[blg5035]

bump for a helpful thread

[BER]

Outstanding info on the ignition switch!

I have printed this thread and it is in a reference folder beside my maintenance manuals.

Thanks for taking the time, and for sharing, this valuable information with us.

[jlex]

Useful. Which is the one for the dash lights that everyone says needs to be fused?

[BlueWing]

My 79 SC is different in wire designation and connectivity. It has a radius of spade type connectors. I'm sure there will be some differences in model years as well. Your reference is for what year model.
jlex my 79 has uses black/blue wires for dash lights, highly recommend adding an inline fuse to protect this circuit. Do a search I know there is a really definitive thread on this mod.

Also it would be hard to hot wire as the sockets look shallow but I'm sure a jumper can be made up to send power from the feed to the fuel pump, ignition, DME and anything else needed to drive away. The mechanical section with the key would also keep the steering locked so can only go in whatever direction the wheels are pointed.

Always great info to have available, saves trying to figure out those wiring diagrams when time or availability is limited.

Thanks SpyderMike nice to share wish I had done this on mine when I was digging in to pass on. Time and no camera than.

Terry

[stf996]

Thank you!


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[timmy2]

Terminals are soldered in the plastic body.



Here is a '74 I rebuilt for someone with all new wires and 6 pin connector as someone had spliced into the larger red wires.


z

[Roger at Pelican Parts]

@SpyderMike, this is very helpful advice... have you ever considered writing a tech article for us? You can get 10% off you next order (no max on value).

[SpyderMike]

I will check it out Roger, but really, Dennis (Timmy2) should be writing some tech articles...he knows this stuff.

[930cabman]

Great info, our issue is no incoming power at terminal #30. From what I can tell this is s direct line to the + terminal of the battery?

Granted our 911s is 40+ years, is a rewire in our future?

thanks in advance

[SpyderMike]

What year is your car? This info is from rewiring my 1985.

There are a couple of terminals #30 on the ignition switch - two wire feeds in and one out to the light switch. The two in come in through he bulkhead connector. The one out goes out in teh loom to the light switch. Have you checked for voltage on all? The two feeds in are discrete wires from the battery into the switch, but in the same loom IIRC. They are direct from the battery to the ignition switch through the bulkhead connector. You might check the power at the bulkhead connector and check the single point wiring connection at the battery. I don't think there are any splices or other connections in that run from battery to bulkhead connector.

[SpyderMike]

Using the image above:

[930cabman]

Mike,

Our 911 is a 1975 S model I tracked it down to a faulty ignition switch. During prior testing I did not have 12v at terminal #30, but found the small round six connector plug was loose. After more testing I was able to spin the engine over by shorting #30 and #50 at the harness end. Then I proceeded to remove the ignition switch (a little tricky for an old guy) and checked continuity between #30 and #50 in the starting position. Nothing. A new one is on the way from our sponsor.

thanks for the assistance

[SpyderMike]

Glad you sorted it out!