Advice on ignition switch issue please

[spuggy]

So, a couple of months ago, my ignition switch died. All the lights and fuel pumps etc. came on as normal in the first positions, but turning it all the way around to the Start position just did nothing - no click, no dimming of the idiot lights, no starter action.

I plugged a used switch I happened to have lying around into the harness, and that worked perfectly. So I figured the old switch died, and installed the other one. Everything has been fine until yesterday, when the original symptoms returned.

I guessed that the used switch had given up the ghost, and borrowed another ignition switch (from a later car, an 84). Wasted 5 hours trying to find the new one I bought from Pelican first, but that's another story...

The switch I just borrowed doesn't work, exactly the same problem.

Now here's an odd thing. The local Porsche center lists the electrical portion of the switch for 74-84 as a 911 part number, and 84-89 as a 964 part number (at half the price). Pelican lists the 964 part as fitting 74-89. I had figured that there was probably some extra terminal or something that wasn't used on the earlier cars, but now I'm not quite so sure.

Has anyone fitted the 964 part to an earlier car (pre-84) and can confirm that it works? (just grasping at straws here).

Otherwise, is there anything other than the obvious "a wire fallen off the starter" or "no connection through from the ignition switch" I should be looking out for? Starter itself is a brand new high-torque type with about 1500 miles on it.

Thanks for any help.

[patkeefe]

Andy:
I had an intermittent problem similar to yours a few months back. Turned out that the 12 year old Optima battery had a bad connection internally at the positive post. I bought a new battery, fixed it. There are a lot of electrical actions that get switched when the key goes to start. Seems like you have a faulty connection in one of the terminal 50 actions somewhere. Do any of the wires in the bundle from the switch get real hot when you try to go to "start"?
Pat

[spuggy]

Originally Posted by patkeefe

Andy:
I had an intermittent problem similar to yours a few months back. Turned out that the 12 year old Optima battery had a bad connection internally at the positive post. I bought a new battery, fixed it.

Yeh, I keep casting a cynical eye at the battery every few months, but it reads 12.46V right now and always cranks and starts fine when the car runs... Lights are bright and the fuel pump as loud as ever, so I figure that's not the issue.

There are a lot of electrical actions that get switched when the key goes to start. Seems like you have a faulty connection in one of the terminal 50 actions somewhere. Do any of the wires in the bundle from the switch get real hot when you try to go to "start"?
Pat

Not that I noticed, although I only held it in 'start' long enough to verify that it didn't work, so far. Took most of the day to scrounge an switch and It's dark and cold here now, so I figured I'd look for melted/broken wires, missing connections or flopped earth straps tomorrow.

I just hate having a question mark over the 964-model switch, no matter how small. I much prefer to deal with the minimum number of variables and unknowns at any given time..

[RoninLB]

my stock yellow wire goes to a T a/c connector in the trunk. Every connector has a voltage drop.

my yellow is around 12g, old, and beat. Sometimes when it's very hot ambiant along w/engine it won't trigger the starter solenoid. I then have to go into engine compartment and use the momentary start button i rigged up for engine work.

I will eventually replace stock yellow with a yellow 10g without the trunk a/c T connector.

After confirming the solenoid will operate when jumped at the starter the above is usually the issue.

[911pcars]

"Yeh, I keep casting a cynical eye at the battery every few months, but it reads 12.46V right now and always cranks and starts fine when the car runs... Lights are bright and the fuel pump as loud as ever, so I figure that's not the issue."

FWIW, 12.46V may be on the borderline. "Normal", open circuit voltage is usually 12.6-13.2 or so. Check the voltage during cranking. If it stays above 9 volts, it should be okay. In addition, verify the charging voltage; should be right around 14+ volts.

Sherwood

[rcaradimos]

try cleaning the ground strap,

[LM3929]

Try replacing the rear trans to body strap, it cause a high Resistance, that was what happened to......found out from one of the Up- fix in books.

[Hetmann]

I have the 964 part in my 78SC.

[spuggy]

Thanks for the responses guys - just for the search engine/record, the only difference I can see with the 964 part is that the older 911 switch lets you go from Run->Start, release the key to Run and turn it straight back to Start again.

The 964 switch makes you switch it all the way off before you can turn it around to Run/Start again.

Left the original switch in place - the borrowed one (known to work) made no difference at all, and the fat yellow wire in the harness was live during "start" so...

Remade the connector on the yellow wire at the starter end, thought we had it. Of course, darn thing worked perfectly as soon as I'd got it to the lift anyway, probably because it was hot. Waited a couple of hours at the workshop and it still started, so left.

(I hate to admit it, but I put the car on some borrowed jack stands, grovelled underneath and looked at the starter, couldn't see the damn wires at all and just took it to the wrench. Too much like spelunking for my liking...)

Failed to start again today. Gauges 'kick' a little on the key, sometimes a click from somewhere (actually sounds like the trunk, but that makes no sense).

Gonna push-start it tomorrow AM, get it to the wrench again. Leave it as long as it takes for the symptoms to re-appear, so he can fix the real problem.

As the ground strap is so cheap, I'm gonna ask for a new one "while he's in there" - but not to fit it until after the problem is identified. I wanna keep my nice new starter, but if it's causing a problem, we'll fit the old one... Could've sworn I asked for a new strap during the rebuild. O well.

Be nice if it was as simple as either of those.

[acrylic66]

Originally Posted by Hetmann

I have the 964 part in my 78SC.

Hello, was that the whole 964 assembly or just the electrical part? If the whole assembly went in your SC ok, any problems with it being bigger than the original 911 part?