Two Steps Forward, 15 Steps Back

[jbscheff]

I'm in the process of putting my 1973 911 back together after a complete tear-down and bare-metal respray. I was getting pretty close to done I thought until I had a major setback today. I installed a battery last weekend and I got the blower fan running properly, the windshield wipers working, the interior and glove box working, and the radio. This weekend was to be the exterior lighting, and gauge lighting. I had some success with the exterior lights, but couldn't get the gauge lights working. I found a yellow wire that according to the diagram in the Haynes manual was supposed to connect to the light switch instead of the turn signal switch (marked with yellow circles in the pic below). Connected this and the gauge lights came on.



Then the smoke started. Cut the ignition and pulled the battery cable, then hit it with a blast of CO2 for good measure. A black and blue wire going into the switch melted completely, and then found another black and blue wire behind the gauges melted. Traced it's termination to light in the speedometer.



The light fitting and the bulb were both scorched, although it's hard to see in the pic above. I had installed all LED lighting I had gotten from a vendor on this board, though right now I can't recall who. I'm wondering if a flaw in the LED could have been the cause, or if there's something else. Anyone ever had problems with LEDs causing shorts? Oh yeah, and not a single fuse blew.

Of course I'm also concerned about all the other wiring. Every other wire that had been in contact with the melted wires has some scorching, and possibly melted insulation and exposed wires. Dang. I'll clearly have to replace the illumination wiring loop, and hopefully can find the connecter that goes into the light switch. Anyone know if there's something like clear liquid electrical tape I can 'paint' on the other wires?

[964TargaC2]

There is liquid electrical tape, Home depo and the
e like carry it

/www.amazon.com/s/ref=nb_sb_ss_i_6_18?url=search-alias%3Daps&field-keywords=liquid+electrical+tape+clear&sprefix=liquid+electrical+%2Caps%2C200&crid=P1DCYEFQU24W

[fanaudical]

Contact user Timmy2 about harness repair. He does great work.

These things are notorious for not having proper fusing on the instrument panel lights.

[75 911s]

First off, I'm sorry for your setback. Very good thing that you caught it quickly before more damage occurred. I use the same LED bulbs. I doubt it's the diode directly, If anything I would think it might be when you swapped the bulbs out, they way the instruments are grounded is critical. Also the individual bulbs, some have cardboard insulation sleeves if I remember.

There are also big grounds running off a lot of the backs of the gauges. Did you have all the grounds installed before attempting to connect to power?

Ebay has a nice large laminated color coded diagram. It's way easier to read and follow. I recommend getting those for your year.

Check all your Earths, at the battery, at the engine, at starter, and the main one in that harness.

[kiwiokie]

I believe the black/blue instrument lighting circuit is not fused at all. Best to add an inline fuse even after this is repaired.

[BlueWing]

Here is the link I used for the dash lights.

Everyone should have this done! One of the most cost effective preventative car saving project we can do.

Dash lighting fuse installation

Terry

[jbscheff]

Terry, thanks for that link. I'll be putting an inline fuse on that supply line to the light switch as part of the repairs.

Duane, you mentioned cardboard sleeves on some of the light sockets? If anyone has any info on this, I'd appreciate it. All of my wiring in the luggage compartment (main harness, instrumentation, lighting, ground connections) was brand new from Kroon Harness in Holland. I don't recall any cardboard sleeves. It came with some pretty good connection instructions, so I'm pretty confident about how I hooked it all up, but of course will check it all again.