Hello All: A friend of mine dropped by with an older 12volt Porsche 356 which had been converted to a VW 1600DP (stock, with alternator.) Everything on the car works properly - the car charges up nicely, the alternator light goes out as it should, etc. The exception is the following situation: Car started and running. Headlights (low beam) turned on. Everything still OK. Go to turn engine off via ignition switch/key car won't shut off. Turn OFF headlights and car shuts down. I assure you this is not a joke - I've never seen this in my years fixing cars. Has anyone ever experienced this before - I know the early Porsches and early Beetles have very similar wiring (i.e. lots of current going throught he headlight switch.) My initial suspicion is the alternator light sharing a ground with the headlights, but everything looks good and there are no "hot to touch" wires. Any help or starting point for diagnosis appreciated. Bill.
Another Electrical Mystery
Nov 26, 2006
5 Replies
Pull the Blu wire off the Alt D+ terminal *after* engine has been started and the ALT light went out. If the condition still exists when you go to turn off, then the ALT is not to blame.
If this *does* cure the problem, put a diode in the Blu wire to prevent feedback. Like this:
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Does this car kill the headlights when the Ignition is switched off (as VW's did)? That could provide a clue.
Put a voltmeter on the Coil (+) feed and switch things on and off and see what it takes to make the Coil live.
Speedy Jim
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Jim: re: Pull the Blu wire off the Alt D+ terminal *after*
Do I pull the Alt D+ wire off while the engine is running with lights on? No damage to Alternator? Also: This car's headlights will operate without the ignition on (i.e. headlight switch is always "hot".) Thanks, Bill.
Yes, pull it off whilst running; won't hurt it.
Jim
Jim: I'm having a hard time duplicating the situation .... we've tried just about every combination - even tried it at night (as when it first happened.) Question: Would it do any good to run the headlights off of a relay instead of all the current through the switch? Also, would it harm anything if I just went ahead and put a diode in the D+ wire? TIA Bill.
You can put the diode in and it won't hurt anything.
Adding a relay is probably going to be a lot of work. I would wait on that.
Jim
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