Early 911 Electrical Issues- Part III-Final
01-17-2002, 11:01 AM
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Early 911 Electrical Issues- Part III-Final
Ladies and Gentlemen:
While checking my charging system I had the oil pressure/oil temperature gauge out of the dash, and I was trying to find out if I had 12 volts between the blue wire (D+/61) and the red with black stripe (switched +12v). I turned the ignition key on and . . . no voltage, but plenty of smoke and a nice sizzling sound.
When the smoke cleared I found that the red wire with black stripe had melted most of its insulation, and had arced against the brown ground wires that daisy-chain across the back of the gauges. Some of the sender wires had also arced and melted together.
To make a long story short I have located a supplier for the original german brass connectors and rubber sleeves, and original german plastic-covered wire, including the correct spiral black stripe. Check out http://www.ynzyesterdaysparts.com/ for - they manufacture an RSR harness so I figured they know their stuff. I couldn't bring myself to use different wire and AMP Faston connectors- this would make future diagnosis difficult, and also serve as an acknowlegment to future generations of my ham-fistedness.
Anybody have a guess as to why the arc welding? Only thing I can think of was that I disconnected the positive lead to the trunk lights so they wouldn't bleed off battery voltage while I had the hood open to charge the batteries. But this does not appear to be in the same circuit with the lights. Maybe there was some chafed insulation somewhere.
I now look forward to removing each gauge, marking the back with a permanent marker, putting a wire marker on the wire, and then fabricating a new mini-harness for the backs of the gauges. Fortunately the heater is out of the trunk pending my fuel cell install so I can access the gauges from the back side. Anybody have any advice, other than to not do it again?
Thanks in advance,
John
While checking my charging system I had the oil pressure/oil temperature gauge out of the dash, and I was trying to find out if I had 12 volts between the blue wire (D+/61) and the red with black stripe (switched +12v). I turned the ignition key on and . . . no voltage, but plenty of smoke and a nice sizzling sound.
When the smoke cleared I found that the red wire with black stripe had melted most of its insulation, and had arced against the brown ground wires that daisy-chain across the back of the gauges. Some of the sender wires had also arced and melted together.
To make a long story short I have located a supplier for the original german brass connectors and rubber sleeves, and original german plastic-covered wire, including the correct spiral black stripe. Check out http://www.ynzyesterdaysparts.com/ for - they manufacture an RSR harness so I figured they know their stuff. I couldn't bring myself to use different wire and AMP Faston connectors- this would make future diagnosis difficult, and also serve as an acknowlegment to future generations of my ham-fistedness.
Anybody have a guess as to why the arc welding? Only thing I can think of was that I disconnected the positive lead to the trunk lights so they wouldn't bleed off battery voltage while I had the hood open to charge the batteries. But this does not appear to be in the same circuit with the lights. Maybe there was some chafed insulation somewhere.
I now look forward to removing each gauge, marking the back with a permanent marker, putting a wire marker on the wire, and then fabricating a new mini-harness for the backs of the gauges. Fortunately the heater is out of the trunk pending my fuel cell install so I can access the gauges from the back side. Anybody have any advice, other than to not do it again?
Thanks in advance,
John
01-18-2002, 05:09 AM
#2
Race Car
Yeah, don't do it again! 
I think you are pretty much onto something with the chafing idea. That German insulation gets fairly brittle with age as well.
I figure, you have a '71 911, with some hard miles on it (racetrack)...there's a lot of vibrations, etc. going on in there...so I think you've answered your own question as to why the fireworks?
I think you are pretty much onto something with the chafing idea. That German insulation gets fairly brittle with age as well.I figure, you have a '71 911, with some hard miles on it (racetrack)...there's a lot of vibrations, etc. going on in there...so I think you've answered your own question as to why the fireworks?
