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Why does my taillight fuse blow when I turn the lights on?

furious70

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Out of the blue the taillight/cluster fuse blows when I turn on the lights. The ammeter jumps pretty good when I hit the switch. Been fine since the car was put together in 2010.
68 charger. I think all the gauges and switches were rebuilt at that time (was my dad's then)
 
Sounds like a short in the tail light wiring. Check the harness for spots where a wire might have rubbed through and grounded. Just had the same problem on my 71. Where the harness passed through the bumper bracket rubbed through and shorted.
 
So... the ammeter jumps when you hit the switch, and the fuse blows. What does that tell you ? Time for diagnostic troubleshooting of the circuit.
 
I know the Ebody dimmer switch is garbage, and when I rotate it, it shorts out. I don't know if the bbody is just as bad.
 
Why, because there is a short to ground somewhere on that circuit.
 
Yes, of course there's a short. I stepped into that one a bit lol. Was looking for ideas on something they might have suddenly gone bad. I know the dimmer switch thing, I'll rotate the switch and try again to see if it still instantly blows and then move on from there
 
One simple thing you can do to help isolate the issue. Unplug the rear harness behind the left kick panel. If it does not blow the short is in the rear harness. If it does blow then its dash forward.
 
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Yes, of course there's a short. I stepped into that one a bit lol. Was looking for ideas on something they might have suddenly gone bad. I know the dimmer switch thing, I'll rotate the switch and try again to see if it still instantly blows and then move on from there
All you need to do is troubleshoot the circuit to locate the short. Simple.
 
Yes, of course there's a short. I stepped into that one a bit lol. Was looking for ideas on something they might have suddenly gone bad. I know the dimmer switch thing, I'll rotate the switch and try again to see if it still instantly blows and then move on from there
It could be one of a number of things ....check the following;

* wires inside taillight fitting rubbed through or chaffed
* wires pinched under front bumper brackets or other brackets
* rusty floor pan might have damaged wires from foot traffic over the years
* poorly terminated wiring under dash touching frame or pedal brackets etc
* rust or corrosion around ceiling light rubbed through
* wiring loom going through bulkhead near battery may have chaffed through


....it could be a number of things. First thing to do is to disconnect the front-end lighting plug from the bulkhead connector, and see if fuse blows.
You will go through a few fuses until you narrow down the search....so be prepared.

Next you could try disconnecting the taillight lamps (bulbs if you like) from the fittings - a pair at a time, work methodically, and narrow down the area where the fault is.
Then do the fronts if no change and the fuse is still blowing...then rinse & repeat elsewhere there are lights or devices on that circuit.

Try the console wiring (if fitted) especially if you've had the seats out recently - or at least since the fault has been present.

Think back to when the fuse was OK, and what you did after that.

I would suggest using a series lamp for testing (saves blowing fuses) - but unless you're competent with electricity, it would be difficult to explain the process.
 
Yes, of course there's a short. I stepped into that one a bit lol. Was looking for ideas on something they might have suddenly gone bad. I know the dimmer switch thing, I'll rotate the switch and try again to see if it still instantly blows and then move on from there
Personally, I'd start in the trunk. You may have had something in there that moved around and bumped a wire. After that, yank the door sill panel and check under the driver's side. just my $0.02
 
All good ideas, thanks. I haven't had it out at night for awhile so I'm just going to have to isolate the sub harnesses as y'all suggest
 
One other question. This car has one of the crappy repro turn signal switches in the column and it has always intermittently acted up. Can there be a short in there only when the lights are on but operate ok with them off?
 
One other question. This car has one of the crappy repro turn signal switches in the column and it has always intermittently acted up. Can there be a short in there only when the lights are on but operate ok with them off?
No.
 
One other question. This car has one of the crappy repro turn signal switches in the column and it has always intermittently acted up. Can there be a short in there only when the lights are on but operate ok with them off?
Any doubt just unplug it and try the lights.
Same with the dash light dimmer switch.
 
On my 69 the cigar lighter is on the same fuse circuit as the tail lights, the new lighter socket I installed was shorting.
 
All good ideas, thanks. I haven't had it out at night for awhile so I'm just going to have to isolate the sub harnesses as y'all suggest
Don't forget to report back with the findings. :)
 
Get a 1157 bulb and socket. Using clip leads wire this across the terminals of the fuse that blows. It will GLOW BRIGHTLY as an indication of a short. Then you can disconnect various harness and look for the glow to go away as you troubleshoot.

Keep in mind the sockets themselves can short. The contact springs can break and short to the connector shell (which is Ground). Good Luck.
 
It's the rear harness, unplugged that and it's ok.
With lights off the turn signals with, brakes work, hazards work. Does that mean I know that the issue is with a running light wire and not any of the sockets? Or one bulb element?
 
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