I've been messing around lately trying to install my tachometer....and now my dash lights no longer work...

i checked all the fuses. i actually know which fuse controls the dash lights, and put a test light up to it. when i turn the switch, the test light works. when the fuse is back in there, it doesn't work. ?? tried a different fuse and everything. tried different dash bulbs. nothing. i know it's drawing power, because the clock dims a bit when the switch is on.

it's my guess that the ground on that particular fuse block is shot somehow? to reinforce that theory....i added one of those "add a circuit" connections at that fuse block, and ran it to my illumination light on the tach. when i flip the switch for the lights, the tach lights up like a champ now......but the dash lights still remain off. but if you think about it, the tach has it's own ground......so it works. back to my original theory that the ground on that particular fuse block is maybe shot?

my only other guess is that the circuit is somehow fawked at the dimmer switch since i was messing around with that. i checked all my soldering, and everything looked good. i'm confused. another thing I might try is putting a jumper before the dimmer switch to see if that is actually shot. i don't see how it could be though. the design is ridiculously simple, and it looks like all the connections and contact points are working when you rotate the dial.

any ideas?

Did you try turning the dimmer knob to see if maybe you had it turned all the way down? Sounds crazy and all, but I spent an afternoon chasing down dashlight gremlins a few years back only to find I had done it.

Pretty strait forward circuit, make sure the connection is tight and there isnt any debris in the backside. Dash lights wont operate if the dimmer isnt connected.

~Darin <img src="/forums/images/graemlins/baby.gif" alt="" />

Try disconnecting the tach light from the dimmer circuit temperarily. If the dash lights now work, then something is connected improperly with the tach light. I've found the best approach is to avoid connecting grounded backlights to the dimmer circuit. I've got enough other un-lit gauges and switches now that I am planning to add a second dimmer rheostat to supply all those items. This one will be wired to work off of the power side: 12V-dimmer-backlights-ground.

<img src="/forums/images/graemlins/lol.gif" alt="" /> The first thing I tried was the dimmer switch. No dice though.... <img src="/forums/images/graemlins/frown.gif" alt="" />

Right now, the tach 12v supply and illumination wire is disconnected from everything. The only thing hooked up on the tach is ground and signal.

They still do not come on. ?? Everything should be completely back to stock now. All the wires I tapped into have been re-soldered and covered up. This is what confuses me the most. I'm guessing by adding that "add-a-circuit" to the dash light fuse block, i somehow messed something up......because the problems happened right after I did that.

4Crawler: Is the backlight circuit basically... 12v - fuse - dimmer - backlights - ground?

I appreciate the replies guys....

Nope, as I posted earlier, it is 12V-fuse-backlights(all in parallel)-dimmer-ground.

thanks for the reply! i'm gonna have to pull out the test light again, and go through everything.

There is a ground next to the kickpanel fuse box.. I assume this is the ground for the dash lights (4crawler? yes/no?). Try cleaning that up and see if it helps. Just a thought..

-Scerb

YEs, main cab ground point is in the driver's side kick panel, look for a bolt with a bunch of brown wires running to it. Remove bolt, wire brush all the spade lugs and the bare steel where they attach then reassemble and tighten.

You might also see if the dimmer rheostat has not opened up. I imagine it is in the 0 to a few ohms range, resistance-wise.

The ground is in good shape. I actually tapped into that ground for both my driving lights, and the tachometer.

I think I found the problem last night. I pulled the rheostat plug back out, and put a test light on it...and flipped the switch. Nothing. Hmmmm.. Peeled the tape off, and checked out my soldering job again. Put the test light on the bare wire, flipped the switch......and BINGO, the test light lit up! When I was messing around with it the other day, I somehow pulled about 90% of the wire away from the plug, so it wasn't making any contact. I couldn't see this, but it was broken underneath the wire sheathing. The break is way too close to the plug to solder back together properly, so basically, to do this right......i'm prolly gonna have to snip a another rheostat plug off a salvage yard unit and leave myself with a few extra inches of wire.

I'm not 100% sure this is gonna solve my problem until everything is hooked up again.....but i'm guessing this was the gremlin.

Thanks for the help guys!