Update - Blowing Turn Signal Fuse
 

1973 Trans Am

I posted some time ago about problems blowing my turn signal fuse. Lots of trouble shooting starting with the sockets - many of which were badly corroded. Over the course of time, I replaced the rear taillight harness, the front light harness, and the turn signal harness in the steering column. Also replaced every bulb - LEDs out back, and Incandescent in the front turn signal and side markers to preserve the GM 'Floating Ground.' Still had intermittent fuse failure for the Turn Signal Circuit.

Tach power feeds off of the IGN tab on the fuse box - directly adjacent to the Turn Signal fuse. In hindsight, every time my turn signals would fail, I noticed erratic tach needle movement. Not that the tach went stone dead - but the needle wasn't steady and would drop completely, then come back to life. The tach came back to normal once I swapped in a new fuse for the Turn Signals.

But there's more - as long as I accelerated gradually and steadily, I got I nice, steady tach reading. But if I ever stepped on it hard, the tach would bottom out and then return to normal operation once I let off the throttle. This was with a known good fuse in the turn signal location and the turn signals functioning properly.

Turn Signals died the other day and when I swapped the fuse, I figured 'what the heck' and moved the tach power wire up to the ACC tab - one slot above the IGN tab - no longer adjacent to the Turn Signal fuse. FWIW - the ACC tab is between the Tail Light fuse (20 amp) and the Radio fuse (10 amp) and I have no radio in this car.

Now, everything works perfectly: tach gives steady readying all the way up to 5500+ (repeatedly) and turn signals work for as long as you choose to leave them engaged.

Somehow - drawing power for the tach off of the IGN tab adjacent to the turn signal fuse overloaded that fuse. And moving it up to the ACC tab feeds steady 12v to the tach - no more bottoming out on hard acceleration. Also - when I got home, I hit the lights and the tail lights function as they should. So, running the tach off the ACC tab (adjacent to the tail lights fuse) isn't overloading that circuit as it apparently was doing with the turn signal circuit.

Everything seems to work fine now, but maybe its time for a new fuse box???

Check your reverse light circuit for a short. From neutral safety switch to tail panel.

My reverse switch appears to be fine. I can fire the car up, put it in reverse and run either turn signal for as long as I care to leave it engaged. It seems as though running the tach off the IGN tab has some sort of draw on the adjacent turn signal fuse. Relocate tach power to the ACC tab and everything works as it should. Somehow, the IGN tab is drawing against the turn signal fuse.