JHZR2
Staff member
This thread is related to my work on my new 93 300SD. Trying to fix the alternator D+ circuit, which I have a thread on. This is a technique question, so I think it’s worthy of its own thread.
I know there’s no conductivity on a length of wire that’s a few feet long. I can access both ends. I know there is at least one discontinuity based upon multimeter testing.
I’ve tried a tone generator, but since it’s such a small closed area, they really just don’t work. If the sensor tip is in the same horizontal plane as the signal generator, the unit will make noise and result in a situation where we really have no idea what’s what.
My thought is that I think one can use an AC non-contact tracer to find presence of an AC voltage through layers of wire insulation. Thus my next approach would be to take AC power, through a variac, and put some small amount (30-50VAC?) on the one end of the wire, to see if the non contact tester finds it.
I’ve seen some videos where someone has a hot lead just sitting someplace, and the non contact tester picks up the voltage right to the end, then rapidly goes off. That’s what I’d like.
So I’m thinking:
AC outlet - switch - variac - ac wire hot only - alligator clip - D+ cable - unplugged connector.
When I run the non contact tester on the D+ cable it should see the AC voltage up to the point where the break is. Then I can open the harness there.
The risk is if the cable insulation and the harness insulation is enough to make it impossible to sense.
Skin dielectric when dry is around 50v. So keeping the AC voltage less than 50 should make it relatively safe. The NCT avoids handling any wire. Granted I’m doing this on my back.
Any thoughts on this approach? Any better ideas on how to pinpoint the spot that it is discontinuous in the harness that is currently closed and sealed up?
Thanks!
I know there’s no conductivity on a length of wire that’s a few feet long. I can access both ends. I know there is at least one discontinuity based upon multimeter testing.
I’ve tried a tone generator, but since it’s such a small closed area, they really just don’t work. If the sensor tip is in the same horizontal plane as the signal generator, the unit will make noise and result in a situation where we really have no idea what’s what.
My thought is that I think one can use an AC non-contact tracer to find presence of an AC voltage through layers of wire insulation. Thus my next approach would be to take AC power, through a variac, and put some small amount (30-50VAC?) on the one end of the wire, to see if the non contact tester finds it.
I’ve seen some videos where someone has a hot lead just sitting someplace, and the non contact tester picks up the voltage right to the end, then rapidly goes off. That’s what I’d like.
So I’m thinking:
AC outlet - switch - variac - ac wire hot only - alligator clip - D+ cable - unplugged connector.
When I run the non contact tester on the D+ cable it should see the AC voltage up to the point where the break is. Then I can open the harness there.
The risk is if the cable insulation and the harness insulation is enough to make it impossible to sense.
Skin dielectric when dry is around 50v. So keeping the AC voltage less than 50 should make it relatively safe. The NCT avoids handling any wire. Granted I’m doing this on my back.
Any thoughts on this approach? Any better ideas on how to pinpoint the spot that it is discontinuous in the harness that is currently closed and sealed up?
Thanks!