Dash lights cause fuse to blow.

[1975NC280z]

Good evening all,

I've searched through the forum, but can't find a similar issue to mine, so here it goes.

I've got a 1975 280z, and I'm trying to hunt down an issue that's keeping me from having dash lights. I can turn the headlights on, including the brights, but as soon as I turn the dial for the dash dimmer the wire in the rheostat burns up. If I turn it to the brightest setting (doesn't use rheostat wires, just straight contacts) a few dash lights come on, then the fuse glows red-hot and blows. The wires to the rheostat get pretty hot too, as does the combo switch. The car is all stock electrically, and I've hooked up a test light and there aren't any shorts I can see.

I've started testing the combination switch, since it's getting warm even with the dash lights off, and found that the green/white wire has continuity to the white/red and solid red wires, and all also have continuity to the metal body of the combo switch. I disconnected the switch and tested it, and no continuity on those points, it's just in the wiring harness itself. White/red and red have continuity prior to the switch, something along the lines of 4-5Kohms. Should these wires have continuity, and what might be my issue? I've checked the car's schematic in a manual I have, and ensured all bulbs are the correct wattage as well. This issue is driving me mad!

On a side note, my passenger front combination turn/marker light has a corroded socket, but that wouldn't be enough to cause such an issue, could it? Any help is greatly appreciated, I've posted on Ratsun, but no one has responded yet with a solid answer.

[Captain Obvious]

Recent discussion on the same issue. Maybe some help in here?

http://www.classiczcars.com/forums/electrical-s30/53259-parking-interior-light-fuse-melting.html

[SteveJ]

Yep, I thing post #12 might work.

[1975NC280z]

So I've started testing the car per post #12, and the only gauge I have left to pull is the speedometer, I've got a dash-cap so it's causing some difficulty in removing the gauge. I'm hoping to have it out by tomorrow morning, and crossing my fingers that this issue is one of the lights in the speedo. Thanks again for the advice!

[Captain Obvious]

Good luck and keep us posted!