What did I fry?

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michaelh712
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What did I fry?

Post by michaelh712 » Mon Feb 20, 2012 5:22 pm

I installed new headlights and all went well until I accidentally let the parking light short out. Everything was fine up until that time. After the ZAP, no lights, no dash lights, no starter, turn signals, nothing.

Batteries are fully charged, and I'm getting 24+ volts at the starter. However, when I measure at the starter switch, I get 2.4 volts. My red wire at the molex is bypassed and goes into a 100 amp circuit breaker, and I get 24+ volts there also. No circuit breakers are popped either.

Its as if I zapped a fuse or relay, but I can't see one inline to the ignition switch.

Collective problem solving and suggestions great fully appreciated.

BTW, in searching; the forum for answers, it would appear that many of us are electronically challenged or occasionally find ourselves with electrical gremlins.

thanks,
Michael
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edzz
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Re: What did I fry?

Post by edzz » Mon Feb 20, 2012 6:06 pm

Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt.

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pcolette
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Re: What did I fry?

Post by pcolette » Mon Feb 20, 2012 6:12 pm

The parking lights are on 2 separate circuit breakers - left front & rear are on #1 and right front & rear are on #2. Both breakers are fed 24 volts from the same gray wire that goes to terminal 58 on the headlight switch.
Other than that I'm afraid I don't have much to offer. Is it possible that the red wire to the starter from the ignition switch melted somewhere along the way? I'd check for continuity from the starter to the ignition switch.
Hopefully one of the electrical wizards will chime in :|
Paul C.
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'73 Swiss 710M
'89 Puch 230GE
2002 MB G500 (For Sale)

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Jim LaGuardia
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Re: What did I fry?

Post by Jim LaGuardia » Mon Feb 20, 2012 8:21 pm

Try bypassing the battery ground key switch. Use a jumper cable from the neg side of the battery to ground, also look at all the under dash connectors with the fat red wire in the main harness. No ground or dirty connection
Cheers, Jim LaGuardia
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"Arch Magus of Machines."

michaelh712
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Re: What did I fry?

Post by michaelh712 » Tue Feb 21, 2012 7:29 am

Thanks guys, I'll try these if it stops snowing.
Michael
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Jimm391730
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Re: What did I fry?

Post by Jimm391730 » Tue Feb 21, 2012 11:16 am

Batteries are fully charged, and I'm getting 24+ volts at the starter
Ground referenced to Chassis? Or Battery negative?
However, when I measure at the starter switch, I get 2.4 volts.
Assuming more likely possibilities, the wire and/or connections between the starter and the switch are bad. I don't think that you pulled enough current to "smoke" the wires to ash, but you very likely could have created an arc in a poor connection that is now an open connection. Check to see that the nut on the rings at the starter are tight (seems they tend to be loose on many trucks), next likelyhood would be the crimps in the terminals. Lastly check to see that the wire did not fuse open. There are "fuseable links" which are wires that are intended to fuse open without melting the insulation within the wiring harness that are there as the last resort to prevent electrical fires, but I haven't seen any good identification of them within the wiring harness. An ohmeter will help you to find any open wires/connections, but be sure to disconnect the truck batteries before doing resistance checks.
My red wire at the molex is bypassed and goes into a 100 amp circuit breaker, and I get 24+ volts there also.
This is sort of a side connection, where the power from the alternator gets into the truck system. Sounds like the problem is down stream of there.
Its as if I zapped a fuse or relay, but I can't see one inline to the ignition switch.
There isn't any.
Jim M.
712W and 710M

michaelh712
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Re: What did I fry?

Post by michaelh712 » Tue Feb 21, 2012 3:59 pm

SUCCESS! Ya need to love problem solving to keep these trucks going, and you need to belong to this great forum for answers.
I checked and rechecked my prior work, but with the same results.

I ended up running a new power lead to the ignition switch, and VOLLA, lights, action. I permanently ran another power lead to the switch and isolated the old one. I'm surprised that short a short zap could damage the big lead wire, but with 40 year old wiring, anything is possible. Next time I'll disconnect power first.

Thanks all for your help

Michael
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