I've had this problem since I've owned the truck. Never bothered me enough to "really" work on it till I got to this point in the "fix up things" processes.
My front turn signal lights always were weird. When I pull the switch on to the marker light position (or headlight too), my dash (turn signal) light stays on, on the right side only (pass side). When I turn on the turn signal, or hazard lights, it shows them to be working/blinking (but when I stop them, the right light still stays on, in the dash). Looking at the turn lights in front of the truck (just under the grill for '76), the right side is not working, but the side marker light is.
Here's the weird part. I changed the left side (turn signal assembly)to the right side and it works. I figure it's got to be the "turn signal housing assembly" on the right side screwed up (correct?). So I go to the wrecking yard and find two more "turn light assemblies", part #48446/3489506, bring them home, clean them up, and install them. Now I have both turn signal dash lights staying on, and no working in the front at all (turn signal, flasher, nothing!). So I put the orig. one back in the left side again. Now it's working again. Swap it over to the right side, it works there too (but the new ones from the wrecking yard will not work on either side, along with the orig. one on the right side. Also when I pull the bulb out of the right turn signal (installed in the truck), my side marker light coms on, and blinks too.
To recap:
I (NOW!) have four turn signal assemblies, correct part #'s for my '76 truck 48446/3489506. Only one works in the truck (no matter what side I put it on). The other three, I can't get to work correctly, no matter where I install them.
I've changed the turn signal "clicker" (from Rock Auto) in the steering column.
I've changed both signal stats in the fuse box, fuse too.
Continuity is perfect in all four turn signal assemblies.
I have power to the pig tails to power up the turn signal assemblies.
I show power to the bulb in the turn signal assembly when installed, but can't get the bulb to light up!"?" WTH!!!
Bulbs are new 1157A (yellow color), plus I have a crap load of older bulbs 1157's, I tried a bunch of them, nothing. Also put dielectric grease on everything.
Damn it, I'm stumped!
Here's a pic of the assembly in question.