Electrical suddenly dead

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Nicolas Derumeaux
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Electrical suddenly dead

#1 Post by Nicolas Derumeaux »

Hello,

I have a 1965 356c since a year. And my first post on the forum.
Drove it in my neighbourhood late with all lights on. Including the fog lights. After 2 minutes the engine shuts off. Can not start the engine and nothing works on the car.
The battery and connections are good, checked the ground strap and that is good.
How to fix this. Thanks for your help.

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David Jones
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Re: Electrical suddenly dead

#2 Post by David Jones »

Check the smaller red wire on the positive terminal of the battery. If that does not make good contact that will cause your problem. For electrical circuit information refer to the registry web site tech info and wiring diagrams.
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Re: Electrical suddenly dead

#3 Post by Michael Branning »

Go to this page for 356 Electrics books. https://porsche356registry.org/content. ... _id=508436
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Nicolas Derumeaux
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Re: Electrical suddenly dead

#4 Post by Nicolas Derumeaux »

David Jones wrote: Tue Aug 02, 2022 12:16 pm Check the smaller red wire on the positive terminal of the battery. If that does not make good contact that will cause your problem. For electrical circuit information refer to the registry web site tech info and wiring diagrams.
Hello Dave

I will check this.

I took a quick look on the troubleshooting guide and there is an explanation for each component but did not found an explanation/fix on a complete shut off.

Thanks for your help

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Re: Electrical suddenly dead

#5 Post by C J Murray »

It could be a sudden catastrophic battery failure. That happens sometimes, like when my wife used my 5 year old Corvette Z06 to visit some friends and the car died at the toll booth. Unhappy wife! It ran fine until the engine speed went to idle and the alternator didn't provide enough juice.
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Nicolas Derumeaux
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Re: Electrical suddenly dead

#6 Post by Nicolas Derumeaux »

David Jones wrote: Tue Aug 02, 2022 12:16 pm Check the smaller red wire on the positive terminal of the battery. If that does not make good contact that will cause your problem. For electrical circuit information refer to the registry web site tech info and wiring diagrams.
The wire from the +pole to the fuse box is good. There is 12 volt.
Can the key switch has an sudden failure that shuts off everything while driving?

Nicolas Derumeaux
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Re: Electrical suddenly dead

#7 Post by Nicolas Derumeaux »

C J Murray wrote: Tue Aug 02, 2022 1:08 pm It could be a sudden catastrophic battery failure. That happens sometimes, like when my wife used my 5 year old Corvette Z06 to visit some friends and the car died at the toll booth. Unhappy wife! It ran fine until the engine speed went to idle and the alternator didn't provide enough juice.
The battery is good but changed with an other to be sure. Same problem

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Re: Electrical suddenly dead

#8 Post by Nicolas Derumeaux »

The red cable goes to fuse number 2. Removed the fuse and it is broken. You have to remove it to see it.
Hopefully a new fuse will fix it.
Thanks

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Re: Electrical suddenly dead

#9 Post by Ken Tuvman »

Nicolas Derumeaux wrote: Tue Aug 02, 2022 1:32 pm The red cable goes to fuse number 2. Removed the fuse and it is broken. You have to remove it to see it.
Hopefully a new fuse will fix it.
Thanks
Or a short caused fuse to blow

Try replacing fuse & drive with all lights off & if all good, turn on fog lights & if all good turn on headlights
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Re: Electrical suddenly dead

#10 Post by Mike Wilson »

And make sure the fuse is the correct amperage.

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Nicolas Derumeaux
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Re: Electrical suddenly dead

#11 Post by Nicolas Derumeaux »

New fuse in (16amp) and things are working now.
I will test the headlights and fogs. Thanks for the tip

Thanks David for pointing me in the right direction

During my search I checked the ignition switch and while removing it from the dash the red and black wire disconnected from the switch. I’m not sure that they are now on the right place. Somebody has a picture from the switch with de wires at the right place (356c)?

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Re: Electrical suddenly dead

#12 Post by Paul S Zuchowski »

There is a great document out in the technical library that will show you what you are looking for. Go back to the Registry home page, then "technical", then "technical library" then scroll to the bottom of the page. Click on 356 Electrics Downloads.

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Re: Electrical suddenly dead

#13 Post by Jon Schmid »

I've had this happen to me twice over the years, once in my 356 coupe and once in my old Chevy S-10 Blazer. Blazer problem: Sudden dead short between two battery cells-no warning but dead as a doornail. Coupe: As mentioned above, a "magically" loose battery cable. Killed the car completely. Luckily, as I was on my way home from work, I was able to wedge the cable back onto the battery terminal enough to limp home for proper repairs. Good luck!!

Nicolas Derumeaux
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Re: Electrical suddenly dead

#14 Post by Nicolas Derumeaux »

Ignition switch is fixed also.

Good to go

Thanks again 🙏

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Re: Electrical suddenly dead

#15 Post by Hugo Karasawa »

Most of the electricss are powered by the red wire that goes from the battery to fuse block 2-3-4, from there it goes to 30 on the lights switch, from there it goes to 30 on the ignition switch. If that cable gets disconnected all the electric system fails. The large black cable from the battery is there only to power the starter and to charge the battery.

Fuse 2 is only for the clock and cigar lighter. I think the fuse you are using is to large if your car has been converted to 12V.

If you want to know about the Electric system of your car, read Greg Bryan´s articles on 356 Wiring. Lots of diagrams and information, troubleshooting etc.
Here a list of the articles, Just go to MEDIA CENTER - Magazines and look for the magazine you need.
356 Wiring by Greg Bryan
356 Wiring Vol 38#1 May / June 2014
Turn Signals and Brake Lights Vol 38#2 July / August 2014
Instruments and Warning Lights Vol 38#3 September / October 2014
Parking Lights and Instrument Ilumination Vol 38#4 November / December 2014
Headlights 356 B 356 C Vol 38#5 January / February 2015
Headlight Circuit Troubleshooting Vol 38#6 March / April 2015
Fuse Box Ins and Outs Vol 39#1 May / June 2015
The Fog Light Circuit Vol 39#2 July / August 2015
The Ignition System Vol 39#3 September / October 2015
The Starting System Vol 39#5 January / February 2016
The Charging System #1 Vol 39#6 March / April 2016
The Charging System #2 Vol 40#2 July / August 2016
Interior Lights Vol 40#3 September / October 2016
Back Uo Lights and Sunroof Vol 40#4 November/ December 2016
Harnesses Vol 40#6 March / April 2017
6 to 12 Volt Conversion Vol 41#1 May / June 2017
Automotive Electrical Testing Vol 41#5 January / February 2018

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