Brake system warning light and now various electrical gremlins

[70Crew]

I am looking for troubleshooting suggestions. After about 10 minutes at highway speed Friday I noticed that my red brake system warning light was on. I watched it for 5 minutes and it was coming on and then going off intermittently. I got off the freeway and stopped to do a quick samba search (not terribly easy on a phone!). Then I noticed that the warning light was only on when my headlights were on. The brakes seemed to work fine, the fluid was full, and the warning light lit up when pushed. After a quick call to Robbie @ airschooled.net, I decided it was most likely an electrical issue (bad ground?) and kept going.

Two days later I drove back, about an hour and a half at freeway speeds. Again, the warning light was only on when the headlights were turned on. After I got off the freeway I noticed the following:

- brake warning light went off when I braked,
- Brake warning light went off when I used the turn signals.
- Right when I got home I noticed that the left turn signal was not flashing intermittently (no click, no flashing dash lights).
- I parked and got out. When the left turn signal is working inside, it activates both the front and rear running lights, while the right turn signal works correctly.
- In case it might be the source of the problem, I replaced the turn signal with a NOS unit about a month ago. It has worked flawlessly so far.

Any suggestions or sage advice?
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1970 Crew Cab

[kreemoweet]

Bad grounds at the rear bulb holders could cause the brake warning lite thing, and maybe all
your symptoms. Make sure all connections there are bright & tight. You also might have tail light
and brake/signal light wires reversed.
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'67 bug: seized by the authorities
'68 bug: seized by the authorities
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[70Crew]

Thanks! A bad ground makes sense to me given the inconsistent behavior I am seeing. If the wires were reversed, wouldn't the problem have shown up immediately and present itself consistently? Interestingly enough, I did repair a ground tab on one of the tail light housings last month so I will check that. I will also check every ground I can find under the dash.
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1970 Crew Cab

[Cap10323]

This screams grounding issue to me, I would check all your tail light and turn signal grounds.
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-Ian

'77 Westfalia - 2.0 F.I

[70Crew]

Has your bus ever taught you something? Mine has… and continues to. This particular problem seemed odd for a couple reasons; (1) because the problems were so random, and (2) because it was working fine last week. What did I do between last week and now? I re-set the slats in the truck bed. Does that have anything to do with electrical? No…. but it was really the only thing that changed between now and then. Work the problem. Several people thought it sounded like a grounding issue. My first thought was that getting to the center rivets involved my wife playing contortionist around the gas tank (it was a lot easier with the gas tank out). Maybe she accidentally bumped the tank ground or dislodged another wire. I wasn’t looking forward to pulling the back seat and tank dividers out but oh well. Before doing that I popped the engine lid and checked the tail and backup light wires. Lo and behold, I found a rivet head that I had drilled out. It had dropped down on top of the tail light fixture and was strategically straddling the ground and power connections. I pulled it off its’ resting place and went for a drive. Everything is back to normal. Hard to believe that this one small short caused all of those symptoms but it illustrates how interconnected everything is. Thanks again for the suggestions, that helped me focus on the problem rather than just getting frustrated.
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1970 Crew Cab