Turning on high beams turns off all accessories

[jangell]

So this is a weird one: when I turn on my high beams with the key in the Run position, instead of turning on the big beams the accessory relay turns off completely. Turning off the high beams doesn't turn the accessory relay back on. Turning the key off and on again doesn't turn it back on either. It seems there is a very faint trickle of power -- turning off the headlight switch dimly lights the LED dome light. If I leave it off long enough (a few minutes), I can turn the key and the accessories come on again, but turning it on the high beams again turns off the accessory relay again.

Oddly, in one case I had the headlights and high beams on when I turned the key, and everything came on. But turning off the headlights turned off the accessory relay again as above.

Now, the tricky but here is all the work I've done on electrical recently:
- New fuse box
- EFI conversion

This is the first time I've powered up the car since doing either of those (I'm up to the point of testing my EFI wiring). Surprisingly, everything else appears to work (turn signals, blower motor, cooling fans, turn signals, etc). .

No fuses are blown. Mostly I'm wondering: does anyone have any idea what would cause the accessory relay to turn off like that? There doesn't seem to be a thermal trip or circuit breaker or anything like that in the circuit. Any thoughts? I realize the customized wiring might make this hard to give advice on, but I'm hoping someone knows something obvious that I'm missing.

Thanks!

-- Joe

[jangell]

Ok, slightly weirder: it seems that if I touch the positive probe of my multimeter to the positive battery jump post near the bulkhead connectors, the accessory relay turns on again. After doing this a few times, I can now turn on the high beams without any problem. All the connections are tight (I'm going to check again just to be sure), but it's really really weird...

-- Joe

[David T]

Ok, slightly weirder: it seems that if I touch the positive probe of my multimeter to the positive battery jump post near the bulkhead connectors, the accessory relay turns on again. After doing this a few times, I can now turn on the high beams without any problem. All the connections are tight (I'm going to check again just to be sure), but it's really really weird...

-- Joe

When you have weird electrical problems the first thing that should come to mind is a grounding problem. When you lose proper continuity to ground the electric will backfeed into other circuits trying to get to ground. Try to find where the circuits having the problems are grounded and check that.

[jangell]

Aha! It was user error. The bolt on the inside of the car on the back of the jump post was loose. Touching the post with the multimeter must have jarred it slightly. Tightening it up fixed the problem.

This still strikes me as a rather odd manifestation, though. But at least it's fixed!

-- Joe

[jangell]

Thanks! The reason I replaced my fuse box is because it was partly melted, likely due to bad grounds. While I wait for my exhaust to come back from DPI I'm going to run a new ground bus the length of the car, as described here: http://dmctalk.org/showthread.php?1360-Ground-Bus . I don't want my headlights going out on a rural road at night because the fuse slipped out of the melted fuse box ever again.

-- Joe

[Jonathan]

Wow, that was quick!

Glad you got it fixed though. As I read the comments, I wondered if something was sticking, like a relay intermittently staying in one position or another?

Anyway, sounds like that wasn't it. Good example here though that new issues can often be tied to recent work done, even when you think you got it all back together properly or didn't bump or alter anything else on the car while doing so.

[jangell]

Honestly, I'm surprised that this seems to be the only thing I got wrong so far. Now back to figuring out why MegaSquirt is only reporting 6.1v instead of 12v when in the car, but works fine on the bench...

-- Joe