A few weeks ago I posted about a problem involving my dad's 1982 truck headlights not working. After some investigation and swapping the tail light relay with the headlight relay it's obvious that there's no relay 'click' when flipping the headlight switch (but there is when turning on the tail lights, which work.)

I would guess that the problem is between the switch and the relay. Would anyone know the likeliest culprit and how to test for it? I have the FSM with wiring diagram but am no expert at reading the diagrams. I'm not sure which pins on the steering column wiring connectors (that lead to the relays) are the ones to test.

Or maybe there's another problem between the switch and relay, in which case I'm all ears. The wiring from the column to the relay looks good at a glance, no fraying at all that I can see, though that may or may not mean anything in a 30 year old truck.

As for other things, I've cleaned the ground straps and connections at the voltage regulator and on the passenger front side near the belt tensioner and on the passenger wheel well below the battery (as well as purchased a new battery ground strap.) I'm not sure where the other ground straps might be, though I understand there's one in the crossmember in back, though I'm not 100% sure where.

Thanks for your help!

 

I would try the fuse area first. I've had a little corrosion on there when I had problems. I checked the fuse right off the bat, but it was good. I then did the same things you are doing, which was test all of the connections. I ended up checking the fuse area again and decided to clean it up, and bam, worked perfectly. Who knows, go for the easy stuff first.

 

Well, don't I feel silly. It turns out the problem was with the fusible link (is that the right term?) that connects to the positive battery terminal-- or doesn't, in my case. The plastic connector had worn and had detatched itself from the battery post and was dangling freely. I put it back on and just like that, my dad's headlights and hazards work again.