Dash light fiasco

[roofman]

Oops, this is either the reostat, or I did something when I hooked up my 3rd brakelight. I messed with the car a few minutes today, and popped another fuse. Dash lights not working, tail lights not working, brake lights are working. When I ran wires for the 3rd brakelight, I hooked them directly to the light sockets. I know that they are on the correct socket hookup as they work as they should. Does it matter that these are on the socket and not wired directly to the harness? I hate these things that have 2 potential problems roled into 1.

 

[poolboy]

According to the wiring schematic, the brakes lights, wiper, temp and fuel gauges,heater fan and turn indicators are on the same fuse.
The dash lights, tail lights,license plate and parking lights are together on a different fuse.
Might have you grounded the tail light or parking light (red +) while working on your brake light hook-up?

 

[TR3driver]

The rheostat itself wouldn't pop a fuse, but the short I mentioned before as a possible reason your rheostat failed certainly could. If you had the taillights on when the fuse popped, then I'd start by disconnecting the dash lights at the (former) rheostat and trying again. If the fuse no longer pops, then you've got an intermittant short in the dash lights.

Those can be hard to find, since that circuit runs around so many places. The one on my Stag turned out to be that the wire to the automatic transmission selector lamp (which I don't have) got caught under the edge of the console frame.

But since you said the temp & volt lamps quit first, I'd look in that area first.

If necessary, you can temporarily wire a headlight bulb or similar across the fuse terminals while you are troubleshooting, so you don't have to keep sacificing fuses. The headlight bulb will pass enough current to light the dash lamps, but not enough to harm the wiring harness if there is a short. I keep a supply of "burned out" bulbs on hand for just such a test. (Almost always, only one filament burns out, leaving the other useful for testing.)

 

[TR3driver]

No chance of "burning in the garage", the power to the dimmer is killed when you turn off the light switch.

Randall- You still have power to one side don't you?

Sorry for the delay, just saw this.

No, when the main lighting switch is off, the rheostat has no power at all. Otherwise the dash lights would stay on when you turn off the taillights.

FWIW, I just measured what appears to be a good used Stag dimmer, which should be pretty similar to the TR6. Full scale is 22 ohms, but the control is very non-linear. Taking the lowest resistance point as 0 (going beyond that is open circuit), then the readings are :

0/4 0.2 ohm
1/4 0.5 ohm
2/4 1.8 ohm
3/4 5.0 ohm
4/4 22 ohm