tail light fuse is blowing.

tried unplugging rear harness still blew; only part I could unplug and fuse stopped blowing was the half of harness on engine side of firewall that services headlights. Changed that whole harness from parts car and same thing; changed horn relay same thing. Not sure what or how to continue.

did you unplug the light switch itself? still blows?

Did you have the front park lights unplugged after you changed the front harness?

 I wish I had a schematic for this car.

yeah, i guess that you would need to have the harness plugged into the light switch.

I think the next step is going to have to be to ohm out the park light leads to ground , and see if we can find the short. We are going to have to dig up a schematic , would sure make it easier.

lets start here, disconnect your firewall harness to park lights.
good fuse in , then pull the light switch to park position ... blow or hold ?

IF it the fuse holds, the problem is in the underhood harness.

IF if blows,,, it 's the underdash harness........

SD 396 wrote:

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Does the main power come into the fuse panel via the headlight side of the harness or the engine side?

 

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 IT may, not sure if that has the single harness or 2 piece where 1/2 goes to the engine ,  if that is the case , then power would come from the solenoid??

I will have to help him dig in ?

I have a '68 wiring schematic if it helps but someone here must have a '66 one they could scan. First thing to check is if someone replaced the dash light fuse with a higher amp fuse than the park light fuse. If there is a short to ground in the dash lights the lower amp fuse will burn. And cigarette wrappers are not fuses. lol. If fuse blows only when you turn on the lights problem is after switch not before. According to '68 it's a brown wire to front and back. Let me know if you want it scanned.

Have you tried it w/ wiring left intact but all park/tail running light bulbs pulled?.
If still popping fuses, isolate and remove dash supply wiring from the equation and try again..

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My '68 schematic shows two brown park light wires coming off the switch. ( maybe on the same terminal). One for front and one for back. If yours is the same, find a good spot easy to get at and cut one to find out if problem is front or rear. You haven't isolated out the rear by disconnecting in the trunk. There is still the harness before the trunk plug.

unplugged the hedlights switch on dash and ran jumper from power connector to each post with no circuits blowing. Figered it was the switch but cleaned it up and tried it now seems to work fine; all lights working. No dash lights yet but power to guages ,lighter and interior light.