Old Barracuda's Old Wiring Woes

I hopped in the '66 Barracuda Formula S at church one night in the dark after instrument practice and something strange happened. I turned on the headlights and very soon after I started driving, the dash lights went out and the under-dash "map" light came on. As an added bonus, the two C-pillar dome lights no longer worked, as I'd found out since I was fiddling with the headlight dimmer switch to try and get the map light to go off. Get this, all three map/dome lights are controlled by the headlight switch - it makes no sense why one light would be on steady and the other two won't turn on. I figured it wasn't a big deal to drive home with no dash lights, and they did actually come on (and the map light went out) about halfway home.

Everything's fine, right? Apparently not. When I got home my brother texted me and said he saw no taillights or brake lights when I drove away from church. Hmm. Well at least they probably came back on when the lights "fixed" themselves on the way home. So, today I started digging into the 58-year-old dash wiring (the car was built November 1965). I wasn't sure what would cause this issue, so I started at the headlight switch. The easiest way to get to it was to pull the instrument cluster. It's not a terrible job but it isn't trivial. The steering column also had to be lowered to get the dash out.

Well if that melted headlight connector isn't the problem, I don't know what is. Funny thing though, the wiring doesn't look scorched.

I pulled all the wire connectors out of the plastic blob to check their condition, and they were fine, but yeah, the plastic piece has seen better days so I didn't bother reusing it. I just plugged the individual connectors into the light switch.

After cleaning up the connectors and crimping them to get them tighter, I tested the light switch and everything worked as it should. Good, problem fixed. I reinstalled the switch and the instrument cluster and.................... nope. The problem is back and now it's not intermittent. At least it's a whole bunch easier to fix a constant problem versus an intermittent one. Back out came the instrument cluster.

The next step was then to make sure the under-hood bulkhead connectors on the firewall were making good contact. Yep, they were good.

Now it's time to start chasing wires. I pulled the glove box out to access the map light that was now on all the time. Everything looked fine there, so I traced the wiring the other direction. That led me to the fuse panel. Just one Phillips head screw and it comes out. Just not very far out, as the bundles of wires are clamped in place in a lot of places, to keep things from rubbing and wearing. After some fiddling, I got the fuse panel out far enough to take a look. This next photo shows the top of the fuse panel and several wires crossing over or under each other, and maybe even being pressed into metal terminals. This requires further investigation.

Below is another photo taken with a flash, and yes, the black wire was pressing hard enough on the pink wires that they contacted the metal terminals under them and apparently broke the insulation. I rerouted the black wire under the pink ones and it appears to have fixed the problem. I didn't bother to try and figure out why this issue would cause brake/tail/dome lights to not work, and the map light to be always on. It might have been a funky ground but it's too much for my little pea brain to process at this point in the day.

This last photo was taken after I fixed the issue, but before anything was put back together. Chasing this old wiring issue was a four-hour job.

The next issue with this car is the leaking rear differential. I put the car on the lift, assuming the pinion seal had let go. Nope, that would be too easy. There's oil on the bottom of the diff but no place I can see where it is coming from. It's probably the gasket between the center third member and the axle housing, but I can't be sure. That gasket is a real bear to change, as the axles have to come out of the differential housing. *sigh* The joys of old stuff.

Postscript: 1/18/2024 I snugged up all the third member nuts, and while I haven't taken a really close look, it appears that was the culprit. Now what do I do about the driveshaft vibration... I think a couple of hose clamps are in the driveshaft's future.

Post-postscript: 4/27/2024 Soooooo, I drove the car yesterday from Poulsbo to Shelton and the map light came on again, but it happened when I turned the parking lights on, so I drove without parking lights. Then on my trip home I noticed the map light came on whenever the brake pedal was pressed.

This time I began my investigation at the fuse block under the dash. I removed the one Phillips screw holding the block to the upper side of the lower dash and tried to pull it down some to look things over. Not so fast, buddy. A wire bundle (which I'd mentioned previously as being difficult to deal with) went behind the kick panel, so out come the two screws that hold the kick panel in place. Another not-so-fast-buddy moment, as to get the kick panel out, three screws need to be loosened or removed from the carpeting sill plate, then the sill needs to be pulled back to get a corner of the kick panel out so the panel can then be removed.

Now that the fuse block is more accessible, I noticed one fuse wasn't quite all the way in the clip. It was tight into the fingers of the clip but not quite seated. I pushed the fuse in all the way. Hmm, I wonder what that fuse is for.... Yep, brake/tail/dome lights. I pushed on the brake pedal and the brake lights came on, and the map light stayed off. I removed the fuse and the brake lights didn't come on, and the map light came on. I guess I finally found the real culprit of my lighting issue. Note to self, if the map light comes on when the brake pedal is pressed (or the lights are turned on), it's the fuse. You may notice some of the fuse clip fingers are a tad bit rusty. I may need to fix that. Someday.