Ignition switch replacement - under dash method

[jlynch1960]

My starting was intermittent (84 Carrera) and the advice from the board was that the ignition switch was headed south. I ordered the part (964 613 012 00 XX) and reviewed the methods discussed in various posts here.

Most people removed the entire tumbler/switch assembly from the dash which requires removing two anti-theft shear head bolts that attach the assembly to the dash and a screw that attaches the assembly to the steering lock under the dash. A few were able to remove the switch from directly behind the tumbler (in front really) working under the dash. I did the latter and because some of the info on this topic is a bit thin (i.e. modify a screwdriver to the appropriate length), I figured it might be helpful to lay it out in a bit more detail.

Here's what I did-

Go to the hardware store and buy the two tools pictured below. I believe the one is called a countersink screwdriver. The other is a No. 1 Phillips attachment for a 1/4" socket. They were $8 total at my local gouge hardware store - no doubt less elsewhere.

A good light and small mirror are also helpful but only up to a point.

Disconnect the battery ground.

Remove the driver's seat and lay some heavy blankets over the DME, as you'll be working on your back with your head up under the dash.

There are five wiring harness plugs that need to be disconnected. Three of them are more or less beneath the ignition switch. I believe these are for the headlights and hazard switches. Pry off the ignition switch plug - it's pretty stiff and I had to use a flat screwdriver to get it started. Finally remove the harness plug directly above the ignition switch as it blocks access to the upper screw holding the switch to the tumbler.

It didn't seem necessary to do any labeling - although four of the plugs are the same size they have different pin configurations and are oriented in ways that readily indicate where they will be reattached. If you're not comfortable with that, go ahead and label them.

Gently bend the wiring out of the way.

The switch is attached to the tumbler assembly by two Phillips head screws. Access to the one on the bottom is straightforward.

For the one on the top, use the countersink screwdriver to free it up. The working end of the tool is just long enough to clear the pins on the switch and there is enough room to get about a quarter turn. See the attached picture. There isn't much room at all to work with and you're doing this more or less by feel. You can shine a light up there and see the screw with the mirror, but when you stick your hand up to work there's no visibility.

Once it's loose, use the socket Phillips head as a small screwdriver to draw it out all the way. Once I had it on the screw, I was able to use both index fingers to turn it out - it's that tight a space. Be prepared for cramping in your hands and arms. It's a tight space and you're working in an awkward position so it's easy to get fatigued.

Once the screw is out, the switch pulls right off. Try not to drop it on your face.

Install the new switch (orientation is with the flat side of the center plastic pin facing down). Reattach the bottom screw first - this will allow the top screw to go in more "easily." Again, on the upper screw, this is by feel and it took me a good twenty minutes to get it back in. If you're not sure it's tight, loosen the bottom screw and see if the switch wiggles.

All in it took me about three hours to do this project. I fumbled quite a bit getting the seat reinstalled (first time doing this for me and the clips holding the floating nut plates in the ass end of the rails were pretty worn and didn't want to hold the nut as they should).

You might want to turn the car over before you reinstall your driver's seat. I didn't but it worked out ok anyway.

Take two Advil and a long hot shower to relieve cramping.

Note - this fix does not work if your car keeps running when you turn the ignition off - in that case the small metal tab that allows the tumbler to turn the ignition switch is likely broken and the entire assembly needs to come out.

Good luck - remember, if Uncle Jim can do it, you can too.

[snbush67]

Originally Posted by jlynch1960

You might want to turn the car over before you reinstall your driver's seat. I didn't but it worked out ok anyway.

Don't you think this step would be easier if the car was kept right side up?

Good write up, thanks.

[ossiblue]

Great pics of the tool arrangement you used, thanks. Having had to do this recently, I too used improvisation in the tool dept. One thing, however, was my switch used flat head screws to secure the electrical portion (it's a 73.5). Does anyone know when Porsche went to philips heads?

[schumicat]

Great write up. I would call that tool an "offset screwdriver."

[jlynch1960]

Good question Ossiblue. I have no idea when they changed over to Phillips heads, but it occurred to me reading your post that the flat countersink screwdriver would be worthless if the upper screw is oriented other than in say a 7 to 4 o'clock position - that's about the the radius you have to work with. About a 50% chance you couldn't get the tool in the slot to get it started.

[spuggy]

My '77 still had flat head screws.

This was the only thing I owned I could bring to bear on the top screw to get it started



Once the top screw is loose, faster to just use the bit between thumb and forefinger...

What a pain... You can also get screwdrivers with a bendy (cable) shaft. Which I would have bought ahead of time if I'd known.. It would justify its place in the tool collection the first time it saved you an hour jammed in a yoga position under the dash or somewhere equally awkward

[G450X]

I think I need to change out my switch as well. I sometimes have to attempt the start multiple times to get it to crank (sometimes it just won't start - click, click..). The starter & battery are known good. I just hope it's the switch, and the whole assembly is still good - replacement of the assembly looks like a PITA!

Thanks again....

[RSTarga]

I tried the above with no success and ended up replacing the whole assembly. It really was not that hard, just time consuming and I'm good for another 38 years.

[spuggy]

Originally Posted by G450X

I think I need to change out my switch as well. I sometimes have to attempt the start multiple times to get it to crank (sometimes it just won't start - click, click..). The starter & battery are known good. I just hope it's the switch, and the whole assembly is still good - replacement of the assembly looks like a PITA!

Thanks again....

For me, the irony of replacing the electrical portion of the ignition switch is that this wasn't the problem at all and the original switch has since been re-fitted and is still working 100% years and 20,000 miles later. Because it seemed to work afterwards, I thought it'd fixed the problem, but it was actually dirty connections on the yellow wire's path to the starter solenoid. They'd buzz out fine for connectivity, but (sometimes) wouldn't pass enough juice for the solenoid to work.

Elimination was quite easy, because literally everything else was new or replaced by that time... It was the 14-pin engine bay connector and the bulkhead plug/socket for the ignition switch that was the issue all along. Plugging another electrical switch in "cleaned" the contacts enough to make a difference and fool me that was the problem, until it became a 100% "no crank" issue 3 months later - and yet another ignition switch made no difference at all.

Tracing the yellow wire back (and checking voltages, not connectivity), it became quite obvious what to try next once I separated the 14-pin plug from the socket...