Ignition Switch ? Car keeps Running with key off

[aluminum]

Yesterday I shut off the Key ( 1980 928 US ) but the car kept running ?
I had to Kill the motor with the clutch with the Battery Disconnected and leave the battery disconnected as when connected power is running to the Ignition Even with the Key off ?.
The " Ignition Switch " feels kind of Loose however starts the Car fine and the locking steering wheel still works fine Except now it well not shut off
I am thinking I need a " Ignition Switch Replacement "
to replace the Switch behind the Lock .
Has anyone ever heard of this happening by chance ?
" ALSO > Would something Else possibly cause this to happen ? perhaps I am on the wrong track here
Thanks if anyone Knows or has input that helps

[Alan in AZ]

Try removing the Rear Defroster Relay - that has been known to fail and energize the ignition all the time...

Alan

[aluminum]

Hello Alan
I well give it a try when I get Home or in the AM Thanks Regards
( I was fooling with the Fuse / Relay Panel when this developed > changed the horn Socket and Relay " Had broken off rusty Relay Prongs " )
The Switch Feels Loose and like Its Gutted but has been like since I have had it .

[Mrmerlin]

FWIW do not ever remove the ground strap while the engine is running, as you can easily fry the diodes in your alternator,

since you have done this,
it would be wise to check your charging system,
at 1500 RPM with the lights on you should be seeing 13.5 V or more up top 14.2 V

If the volts wont go over 13.4 then you have damaged the alternator ,
and battery failure will soon follow.

The starter key/ switch is a two piece part,
the front side holds the key,
the electrical part is screwed to the rear of the key portion,
it can come loose its held with 2 screws and possibly a metal U bracket

[Alan in AZ]

Stan is quite correct, it is very unlikely that disconnecting the battery will ever stop a running car - if it actually does stop the car - you may have destroyed an ECU (or your alternator is dead)

Once the car is running the battery is in a mostly passive role just getting recharged while the alternator supplies the system voltage & current. Removing the battery doesn't remove the power because the alternator is still there generating as long as the engine is rotating.

The alternator can only generate well regulated voltage when it is connected to a nice big load capacitor - like a battery. It doesn't strictly generate pure DC but rectified DC with a major ripple on the top - the battery smoothes all this out. Without it the regulator is constantly seeing a changing system voltage and varies the field current to try to compensate. Since it's reaction time can be comparable to the input changes it's seeing these can become compounding and the regulator may vary the field current wildly - vastly increasing ripple noise.

This means your ECUs and all your electronic control units will start getting huge supply spikes potentially many volts higher than any normal running conditions.

Unfortunately this is a great way to kill electronic parts...

Never disconnect the battery when running.

Alan

[aluminum]

Well I hope I did not damage the Alternator or other parts .
it is still Charging ok I well check it when I get the Car Running again .
I Tapped on the Key Ignition Cylinder and then looked under the Dash to discover that the Back Half of the Ignition Switch is Loose and hanging back from the Metal Cylinder / Key > Lock.
I can see the 2 Screws that hold the front part of the Ign. Switch . So the Switch has separated from It's front part . I removed the Rear Part > unplugging it from Wiring Harness . A small Round Bakelite Center Pole that look's to be broken off has also dropped down from the Switch
I see on the Net That Perhaps this Switch seems to be the Same Part number as a 944 as well as many other models also . Perhaps I can get one from a 944 as long as Its OEM as I doubt the after market one's have much life.
I tried removing the Rear Window Relay with no luck
I am wondering why the Switch " Rear Section "Separated from the Front part of the Switch that is held by the 2 screws to the Lock.
Looks like Its going to be Quite a Job to remove the Screws and front part Let alone aligning it all to replace the Switch. Can it be done without removing the Pod ? Perhaps .

[Alan in AZ]

Just buy a new 928 switch from 928s R Us or 928 Intl... ( I think its listed as a 964 part #) don't buy unkonwn brands from eBay as there is lots of real rubbish around..

These are not hugely expensive - maybe $80-$90 last time I looked

Alan

[JhwShark]

I believe you can remove the switch without removing the pod.

Though I replaced mine while replacing the spedo gear...IIRC you just need to be good upside down on your back. I did not replace the front only the black electrical switch component.

[aluminum]

Well I removed the Pod because I could see no way to remove the Switch screws without removing it.However I have Big Hands .
So I well order a Switch.
I am wondering what parts are now Damaged / Burned out / Whatever from the bad switch.
Has always been my findings that all Porsche's have the worst Electrical systems I have ever seen related to not working properly . I have had 3 and still have 2 and all are the same with less then 1 star on Electrical . Kind of a toy car in that respect. It's the handling that I love
I am thinking that perhaps Starting power went to to the Ignition / Computer and perhaps burned it all out we shall see. I have had several Cars / Trucks with almost countless Hundreds of Thousands of miles on them . of all of them I only remember replacing a Headlight switch one time. A 10 Min Job Evan with big hands. None of them handled like a Porsche that's for sure.
So My Order is in > OEM Ignition Switch from Pelican $94 with free shipping and a $10 Web Discount . I hope that's a Original Porsche Switch or do I Hummm ?

[Alan in AZ]

That the car continued to run means that most likely everything else will still be fine... Despite everything the modules in these cars are still fairly reliable - they are just very old now. Other reliability issue are usually due to corrosion over time, high humidity doesn't help but a good cleaning really does help for this.

Not disconnecting the battery obviously applies to all modern cars for the same reasons.

Did you ever test by pulling the rear defroster relay - I still think this is always the most likely cause of what you described.

Alan

[aluminum]

UHello Alan
Yes I did Pull the rear defroster Relay (I Previously Mentioned Post's above )
I Thought Hard before Puling it as It's a Long Double ( my word ) Relay and was stuck hard and fast in the socket . I have learned to " Rock " / twist and Pry on these relays .
However if the Prongs are rusted most likely you well be pulling the socket to get the Prong out.
I also just recently had the presence of mind to think about getting all Brass or Copper Fuse's rather then Aluminum as the Aluminum is not Compatible with the Fuse Panel and in fact I understand Corrodes it ( and the fuse in it ).
When at a salvage Yard previously I loaded up on fuse's from Volvo's / Mercedes but now I well only get Brass and Copper as spares . I Might mention that I never blow fuses but rather replace them due to Corrosion . I use unused Sockets to replace Damaged Sockets that I had to
Decimate in order to remove them or the broken Prongs in them.
My 1990 911 has Far more Electrical Issues then the 1980 928 I might note by a Easy 3 to 1 at least .
" UPDATE " Friday Am Received the New Ignition Switch From Pelican Via Fedex about 11 am "Wow that's what I call Great service from yesterdays PM Order Next day delivery at no Charge !!!
Switch is A Original Porsche Switch with W Germany Logo on the Switch Bottom and look's the Exact Same as the one removed.
Well the Pod is off so I held the Switch in Lock Cylinder with the Pin alined at the top and connected the battery . No Current Draw Yea. I Started the Car and shut it down all is working normally now.
Tested the Charging at the Battery but with " no Lights " on with a slightly Low Battery and with motor Revved up to about 2 K RPM"S
shows 14.2 Volts with a original Bosch Alternator . > Type that you must rev up to start the Current flow after starting motor
I took that Alternator all apart before I Ever got this 928 running as i was full of spider stuff / dirt and stuck but it looked like new
inside so I have been running it so far with good results .
Motor Update : Motor sounds like normal however I have not driven it yet as the Pod is still off. I wish I had a New Printed circuit board as the End's that hook up to the Connectors are all coming apart. Although when I first got it running a few of the Gauges worked after a while only the Temp Gauge and the Tack worked. I repaired the Speedometer wiring at the rear end and that worked great for about 3 days. Seems to be that at the hook up point on the Circuit board the signals do not go forward to Gauges.
I was planning to get a 170 MPH Speedometer as mine has a 80 MPH one but now am thinking that if It's not going to work anyway what's the point .
Thanks for all the help everyone and happy motoring