C3 Electrical warning
Thread Starter
Intermediate
Joined: May 2007
Posts: 45
Likes: 0
From: New Lenox IL
C3 Electrical warning
I'm new to the forum, and thought I'd share this. I sent it to CF when it happened a couple of years ago, but they didn't print it -- probably not enough general interest.
I have a high mileage '69 roadster (see Electrical Gremlin post for details). A couple of years ago I decided to drive it to work on a nice late spring day. About six miles from home I thought I noticed a strange smell. Within no more than another mile I realized something was burning, with smoke coming from under the dash.
I stopped, popped the hood, and found smoke there as well. The problem was obviously electrical, so I did then only thing I could think of to cut power by cutting the 12V hot line to the alternator. I carry an extinguisher in the car, so sprayed that everywhere I could imagine might be hot, then set to unhooking the negative post on the battery. Fortunately I got to it quickly enough to stop the short and put out the fire.
Two quick lessons here -- the extinguisher was worth its weight in gold, and I now have a battery ground quick disconnect in place.
After having it towed home, cleaning up the extinguisher mess, and opening things up, I found the problem. As a high-mileage '69, imagine how many times the tack cable has flexed, with RPMs going up, then down. The tack cable runs right across the top of a wire bundle that transits side to side. That untold number of flexes wore through both the outer sheath on the tack cable and the wrap and insulation on the wire bundle, until raw tach cable housing (ground) met bare hot wire.
Fortunately, none of the damage was too severe and was fairly easily repairable. As a precaution against a recurrence, I slit a 6" piece of 5/8" heater hose and taped it over the repaired wire bundle, then slit a piece of 3/8" fuel line hose and taped it over the new tach cable, so now there's a good 1/2" of additional insulation between the two.
If you have a high mileage pre-1975 (when electric tachs began) C3 or possible even a C2, you might want to take a look at this. And the extinguisher and negative post disconnect are cheap insurance.
I have a high mileage '69 roadster (see Electrical Gremlin post for details). A couple of years ago I decided to drive it to work on a nice late spring day. About six miles from home I thought I noticed a strange smell. Within no more than another mile I realized something was burning, with smoke coming from under the dash.
I stopped, popped the hood, and found smoke there as well. The problem was obviously electrical, so I did then only thing I could think of to cut power by cutting the 12V hot line to the alternator. I carry an extinguisher in the car, so sprayed that everywhere I could imagine might be hot, then set to unhooking the negative post on the battery. Fortunately I got to it quickly enough to stop the short and put out the fire.
Two quick lessons here -- the extinguisher was worth its weight in gold, and I now have a battery ground quick disconnect in place.
After having it towed home, cleaning up the extinguisher mess, and opening things up, I found the problem. As a high-mileage '69, imagine how many times the tack cable has flexed, with RPMs going up, then down. The tack cable runs right across the top of a wire bundle that transits side to side. That untold number of flexes wore through both the outer sheath on the tack cable and the wrap and insulation on the wire bundle, until raw tach cable housing (ground) met bare hot wire.
Fortunately, none of the damage was too severe and was fairly easily repairable. As a precaution against a recurrence, I slit a 6" piece of 5/8" heater hose and taped it over the repaired wire bundle, then slit a piece of 3/8" fuel line hose and taped it over the new tach cable, so now there's a good 1/2" of additional insulation between the two.
If you have a high mileage pre-1975 (when electric tachs began) C3 or possible even a C2, you might want to take a look at this. And the extinguisher and negative post disconnect are cheap insurance.
