Hey gang...
I think I have a short, but wanna run it by ya'll first.
Item:
'71 Challenger

Problem:
Blowing hazard fuse and when I apply the brake lights, the left side of the taillamps acts funny. When the lights are on, then the brakes applied, the left most bulb goes out and when the brake is released, the light comes back on.....

I just put in a brand new turn signal switch. All body harnesses are new as well.

Check the tail light socket grounds.

Should be grounded through the socket assembly to the body. If the paint or sealer is too thick between the tail light housing and the body you will have ground problems. You could run a wire from the pigtail to the body and that would help.

Michael, the bulb that was lit was on the trunk floor resting on the trunk mat, not bare metal. I will check that the bulb is correct. Thanks.....

Troy

Saga continues........ I got the brake lights to work, so that's a tick mark. But, the 4-way circuit is still blowing fuzes and the turn signals are ALWAYs going now, even in the neutral position. The turn-signal switch is brand new and the wires are not pinched anywhere in the steering column. Now, else where, no clue. I checked the grounding of the front parking like housings and they are good. I will disconnect the rear body harness tomorrow when I get home to isolate that and see if the front works ok. But, something that's weird. Part of the turn-signal circuit goes to the radio? Here are snapshots of what I am talking about.

1. X12-18R goes to the radio ( the hot wire for the radio power feed ), the connection in the dash harness isn't hooked to the radio. The radio in the car is an aftermarket system.

2. The other end of X12-18R goes to the turn-signal flasher.. What the? is this the power source for the radio ( feeds off the turn-signal circuit )?

Gut tells me, with the 4-way blowing a fuse so fast, there has to a short on the body somewhere..... Not, doesn't explain why the turn-signal flasher starts as soon as the key is placed in ignition 1.

All,
I am still having grounding/feedback problems with the turn-signal and 4-way circuit. If I disconnect the forward and rear body connections at the firewall and driver's kick panel, will the circuit still work in such that the flashers and dash lights will work? Or, do I have to have EVERYTHING connected in order for the turn-signal and 4-way flasher to work? I am trying to isolate the circuit to narrow down the possible problem.

1. Check to be sure that you have the correct bulbs. I have seen people put twin filament bulbs in a single filament socket and vice versa. You shouldn't be able to but it can be done.

2. There are grounds are in the trunk drivers side near the rear panel and another one behind the battery. Make sure they are grounded well.

3. Disconnect the rear light harness under the drivers kick panel and see if it fixes the blown fuses. If so check the south end of the car.

4. Disconnect the wires to the turn signal/emergency switch and see if any are grounded to the column. Disconnect the headlight switch and see if it fixes the blown fuse problem also.

Does it blow fuses if the e-flasher is removed? There are two flashers. One near the column and one behind the ashtray. Could be a metal can flasher internally grounded.

Is the dash harness new also? If not check for crispy wires from the alternator gauge and behind the fuse block. It is common for the main power wires to toast and short other wires in the dash harness. I had one that the running lights would not go off but I could dim them from the headlight switch dimmer. Weird stuff happens when the wires melt.

1. Check to be sure that you have the correct bulbs. I have seen people put twin filament bulbs in a single filament socket and vice versa. You shouldn't be able to but it can be done.

I have checked the bulbs, they are proper


2. There are grounds are in the trunk drivers side near the rear panel and another one behind the battery. Make sure they are grounded well.
The ground near the battery is there and in good condition and secure…..

Now, off the top of my head, I can’t recall hooking up a ground wire associated with the rear body harness. Where does it connect? Near the corner of the deck lid by the taillamp housing on the driver’s side?


3. Disconnect the rear light harness under the drivers kick panel and see if it fixes the blown fuses. If so check the south end of the car.

I did that and it didn’t…..


4. Disconnect the wires to the turn signal/emergency switch and see if any are grounded to the column. Disconnect the headlight switch and see if it fixes the blown fuse problem also.
The turn signal harness/switch is brand new. The steering column is loose, so no pinched wires.

Does it blow fuses if the e-flasher is removed? There are two flashers. One near the column and one behind the ashtray. Could be a metal can flasher internally grounded.

I have replaced both flasher with new ones ( same part number from Autozone )…. I will test removing the e-flasher from the harness and turn it on at the column and see if a fuze is blown. But, have to ask, if the flasher is disconnected, how is the circuit complete?


Is the dash harness new also? If not check for crispy wires from the alternator gauge and behind the fuse block. It is common for the main power wires to toast and short other wires in the dash harness. I had one that the running lights would not go off but I could dim them from the headlight switch dimmer. Weird stuff happens when the wires melt.

The dash harness, like all others, is brand new……….. M&H

Tada !!!

The culprit: me...........

I had the pigtail connections on the side mark lights and the front parking lights reversed...... Explains EVERYTHING !!!

Glad I took a break from it all and took a deep breath and went back to the FSM and worked my way from the front to the rear... Luckily, I started at the "broken" end first and saved a LOT of frustration....

I never give up !!!!

Works perfectly.....

You aren't the first or the last guy to do that.