GT6 Gages lose power

[Mitch_GT6+]

1969 GT6+

Well, I need a bit of feedback on this one to point me in the right direction.

I lose power to my fuel gauge and my temp gauge, as soon as I tap the brakes. My brake lights also do not come on. Sometimes, I would drive for 30mins, everything would be good, brake lights and gauges work, then would stop.

I just replaced the voltage stabilizer behind the speedometer, same result.

This started last year where I would lose my gauges, but I didn't realize my brake lights weren't working.

I fiddled around with some wires and replaced some of those older splices with new ones (the green/pink wire I think). Everything there seems ok.

I've taken my "newly replaced brake light from a Ford about 10hrs ago" apart about 10 times, readjusted properly, everything looks good. Bench tested with Oh meter, all good. I do remember before changing it about 10 years ago, the power wire to the switch would get hot. Not so anymore.

One thing to note, my spedomoter sometimes moves in the dash, as I only have one of the threaded brackets holding it. I thought perhaps the angle of the voltage stabilizer wasn't ideal. So I taped the speedometer on the dash so it wouldn't move and no go still.

Interestingly, I did find a black wire with a loop on it, that was loose behind the dash. I figure it's a ground, so I grounded to a metal support behind the dash.

Maybe this should go on the threaded bracket that holds the speedo to ground the voltage stabilizer??

Would appreciate some thoughts so I can figure out my next steps.

Thank you!
Mitch

 

[mezy]

Definately sounds like a bad earth to me. Try grounding out the gauges. Check the ground for the brake lights.
Could try disconnecting the brake lights see if your gauges behave differently

 

[Mitch_GT6+]

Those are some good ideas.

Will start there.

 

[Mitch_GT6+]

Definately sounds like a bad earth to me. Try grounding out the gauges. Check the ground for the brake lights.
Could try disconnecting the brake lights see if your gauges behave differently

Can I ground on the back of the dash, or the steering column? Or any other preferred spots?

 

[mezy]

Just for testing I would take ground straight back to the battery. But if applying the brake effects your gauges I would start on the brake light grounds.

 

[Mitch_GT6+]

Just for testing I would take ground straight back to the battery. But if applying the brake effects your gauges I would start on the brake light grounds.

Ok, right to the battery, perfect.

Is the ground to the brake lights themselves coming back from the brake lights, or through the switch?

I'll check the wiring diagram.

 

[Mitch_GT6+]

UPDATE

I fiddled around as per some recommendations, started with the easier stuff and my test light.

Ran a ground to the battery negative and was grounding the gauges, the brake light switch, the brake lights, etc.

When I was checking the brake light switch, I noticed I didn't have any power going to it on the green wire.

Went to the terminals on the back of the "fuse" box, no power on the green either. BUT, I was showing power on the white wire, which is on the other side of the fuse, which made no sense, as visually the fuse looked good.

I decided to swap the top fuse, and then I had power on both sides of the fuse, power to the brake light switch, gauges were on and were staying on while the brakes were depressed.

Sooooo... Bad fuse it is, but it wasn't shorted at all. Maybe the connections in the end??

Weird.

Appreciate the comments and direction!

Mitch
69 GT6+ (30+ years!)
95 Mini Rover JDM

 

[Sarastro]

Fuses can go bad, like anything else. In my experience, those cartridge fuses used in the TR4/4a (and maybe the GT6? I dunno) will experience a break in the wire from the cap to the fuse element--often because the glue holding the cap in place gets old and comes loose. Oxidation/tarnish on the fuses or the fuse-block clips is another cause.

If the fuse seems intermittent--that is, is seems not to work then does--I'd suggest replacing it.