Blowing Turn Signal Fuse
 

1973 Trans Am. New Tail Light Harness; New Front Light Harness; New Bulbs; New Blinker Relay.

In the garage with the key in the accessory position all blinkers (left and right, front and rear) work correctly and both directions will blink for as long as you leave them activated. I can turn on the marker lights and headlights with either blinker direction activated and everything continues to work as it should.

With the car running, the blinkers will work fine - both left and right - for the first 3-4 uses then they stop working. Get back to the garage and slip in a fresh 20 Amp fuse and everything works as it should. So the blinker relay survives the fuse blowing as do all bulbs.

I have swapped out a couple different sets of 1157 and 194 bulbs to try to eliminate the possibility of a sketchy bulb. Problem persists.

I know the turn signal circuit includes the reverse lights and I have read multiple threads on various forums that swapping the reverse light switch on the transmission solved a similar problem. (This is a manual trans car)

But - if I put the key in the accessory position and slip the car into reverse, both reverse lights come on, they do not flicker and they do not cause the fuse to blow. With that info, am I able to eliminate the reverse light switch as a possible culprit?

I may be digging into the steering column - but it seems odd that both directions work just fine for as long as you care to leave them on with the key in the accessory position - and the fuse only blows when the car is running. Seems like if I had a short in the steering column blinker switch / harness, it would blow the fuse in the garage with in the key in the accessory position, too.

Any thoughts are greatly appreciated.

"fuse only blows when the car is running" ....or is it only when the car is driving? if driving, i think a harness is getting pinched somewhere...something shifts around and pinches a harness. i had a similar issue once.

George

I did go back through both front and rear harnesses and confirmed that there is plenty of slack at every socket, so no pulling or tension anywhere. I also gently removed and replaced the bulbs to make sure that one of the bulbs wasn’t seated just a bit wonky - particularly the dual filament bulbs with the offset pins.

Also found that the front 1157 were from the original harness and were looking a bit tired - replaced with new.

Fired the car up and let both blinkers cycle for extended periods of time - longer than I’d ever sit at an intersection - while hitting every other accessory: wipers, headlights, markers, name it. So far so good. Now its time for a test drive to see if its OK, or (probably) something in the steering column.

Sit in one spot with the directionals on and turn the steering wheel back and forth and see if it blows the fuse.

While I dread the thought of dismantling the top of the steering column and fishing the turn signal switch / harness out, I found a couple of YouTube videos doing the exact job on other GM platforms and it ‘appears’ fairly straight-forward - provided you’ve got a proper steering wheel puller and tool to compress and remove the retainer plate that covers the switch. That may be exactly where this gremlin is leading me.

I had a similar problem...... chased it for years, changed valance housings, adding grounds and changing turn signal switch ( not that bad) it turned out to be wiring harness had rubbed itself in the inner fender. Drove me crazy, it would blow the fuse when I turned the steering right only while moving. Would come home change the fuse would work all day with no issues......

Thank You! Reassuring to know I’m not crazy! Also good to know that you ultimately did trace it down. Lots of rain over the last week since last spending time on this, so haven’t been able to take her on a ‘pressure test’ drive yet. But your post reminds me to stay relaxed, keep track of what I know I have triple-checked and ruled out, and focus on any areas in the circuit where this could be hiding.

Expanding My Skill Set
 

I am steadily expanding my skill set. I ordered a new turn signal switch from American Autowire. I already had a steering wheel puller, so I sprang for a decent lock ring compressor. I watched about 3 different youtube videos swapping the turn signal switch in various GM platforms and went to work. It was probably one of the smoothest ‘projects’ I have ever leapt into.

The stock switch was really filthy, the contacts were a little cruddy and a couple of the wires were bent / pinched pretty good - but no insulation worn down to bare wire - so nothing really glaring. But after getting everything buttoned down, I went for a decent drive, signaling every turn and lane change and the fuse survived.

Here is something curious: in the past, right when the fuse would blow, my tach would bounce around a bit. Then at an intersection, if I hit the turn signal out of habit, the tach would drop from 600 down to 250-300. Turn off the turn signal and the tach would return to ‘normal’ rpms - but it would float around until I got the new fuse in the turn signal slot of the fuse box. On this drive, the tach was dead steady and reacted instantaneously to throttle. Maybe whatever was going on with the turn signal circuit was pulling voltage from the tach??

Anyway - between the new tail light harness, front light harness, all new bulbs, and now new turn signal switch / harness, I think this gremlin had been addressed.

I feel what you’re going through. I’m working under my dash trying to correct 54 years of electrical sins and butchery. Wads of wiring over 12’ long tied up with zip ties. Things cut and disconnected that I don’t have a clue where they went or are supposed to go. Not my favorite thing to try and suss out.


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