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A glitch has been previously reported more than once in prior years, that if rear glass defroster button has been activated on Pod, not sure if by pushing or rotating or both, then car may continue to run. IIRC Alan may have diagnosed this as some kind of alternate path to ground. Not remembering root cause definitively, but remember the events.
Landseer
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so please check if the defrost knob has been turned/pushed
it can be activated via a push for timed duration,
or turned for manual control.
As an aside remove the defroster relay and see the engine continues to run with the key turned off ,
if it does then replace the ignition switch
Mrmerlin
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Heed what Stan suggested though, his recollection is that the ignition switch electrical module is related in whatever root cause analysis or logical pro electrical guru conjecturing was happening at the time. Or he's experienced it first hand in cars he repairs, or all the above.
Landseer
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Check the heated rear window switch. I seem to have in my mind that if the timer relay sticks on, it effectively energizes the ignition circuit causing the car to continue running. Sometimes it is just the push button itself sticking "pushed in"
The heated rear window switch is pushed in and does not pop back out again.
or
The heated rear window timer relay can stick in the on position.
Both causes give the same symptom - +12v is fed into the ignition circuits from the Power to the Heated rear window which is direct from the battery. This keeps the car running when you turn off the ignition.
Once the engine has been stopped disconnecting the battery normally resets the relay, but if the button is stuck in it needs to be pulled back out.
__________________
Jon in OZ
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If you have this issue and need to get the car to stop running, pop the hood, pull the air filter out and hold your hand over the MAF opening to stop airflow. Car dies, and then you can unhook the battery ground strap.
SeanR
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The symptom you describe commonly occurs when a relay that is fed both 30 & 15 links the two together due to some internal fault... This happens commonly with a failed rear defroster relay.
30 is battery direct - input to the ignition switch and direct supply to many relays, 15 is ignition switched supply from the ignition switch - this being powered is what keeps the car running (on with key in position 2,3 [of 0-3]), X is accessory switched power (on with key in position 1,2) , 50 is the starter tip switch to the starter relay (on in key position 3) R is switched radio supply (on with key in position 1,2). P is Park power - used for parking lights (on in key position 0).
Alan
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its not possible to just plug a standard SPST/SPDT relay into one half of the socket - the pins don't match.
You need connect only to Pins 87, pin 30, pin 85, and pin 50 for this (all terminal designations of the rear defroster socket - see realy base)
Bosch Relay Pin - Defroster Relay Pin:
30 - 30
87 - 87
85 - 85
86 - 50
Now for those playing along - on the stock relay the starter (50) when active disables the relay (to preserve power for starting), maintained here.
Porsche also broke convention here with 85 as a positive coil feed, also just maintained here for simplicity of mapping.
Alan.
