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Another Electrical Mystery

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.

Reply to
Bill
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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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Reply to
Speedy Jim

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.

Reply to
Bill

Yes, pull it off whilst running; won't hurt it.

Jim

Reply to
Speedy 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.

Reply to
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

Reply to
Speedy Jim

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