Gauge cluster lighting

Having a challenging time getting the lighting to the gauge cluster to work. I would like to see my speedo at night.

Where are the bulbs??

Thanks in advance!

(btw, I've gone w/ all mechanical gauges in the interim, they light up along w/ the tach when I turn on the headlights)

I wasnt sure if you were talking about the stock ones but I think there are 6 or 7 in the back of the gauge cluster. The bulb sockets that snap into the holes didnt want to stay in on mine too well, so when i first pulled my dash apart I found three of mine hanging out. Maybe that's what happened with yours.

And the stock ones rely on the housing as a ground to complete the circuit. And we all know how good the grounds are on an EB dash!
The aftermarket companies use a separate ground circuit to each bulb for more reliability. Not that this helps in your case, but at least it points out the weakness.
Probably time to pull each one out to make sure it's still in good shape, then make sure it's grounding to everything.

Paul

Stock gauge cluster has two turn signal bulbs, a high beam bulb, and three general lighting bulbs for all the gauges.


Herb

Thanks guys. Yes, talking about the stock gauge cluster. Nothing worked but the speedo when I got it. Trying to get it lit at least!

while you are at it get the led bulbs to replace the old ones. they have them at BCbroncos. OR you could do the illuminating face cover its an aftermarket deal. and is a night and day diff. they have it on a few of the vendors on here.

So the common ground wire appears to be a black w/ white stripe. Does it just ground to the body of the instrument panel, which is then grounded through the attaching screws, or does it go to another body ground position?

I tried the LED bulbs and I still can't see the gauges at night.

barronj said:

So the common ground wire appears to be a black w/ white stripe. Does it just ground to the body of the instrument panel, which is then grounded through the attaching screws, or does it go to another body ground position?

Click to expand...

Negative there good buddy. Arrarr, an electrical pun.
No, that wire is the power to each gauge. The "common ground" here is the metal case of each unit and the main housing to the dash. At least as far as the lights are concerned anyway.
THAT's why it's so problematic. Even the dash isn't always grounded to the body very well, so you can see the potential build-up of issues here.

Actually, the main grounding points for each of the three gauges (water temp, oil pressure, fuel) are each of their sending units. The senders complete the circuit through resistance-to-ground through the body of each. A rheostat in the case of the fuel sender(s).

Paul

What's the fix for the lighting? Run a new strap/ground from the back of the gauge panel to the body?

Yes. OR, for simplification, run one from the cluster case to the dash, then from there to the body. That kills two birds with one stone. Getting the dash ground up-to-snuff too.
Then make doubly-sure that your main grounds form the engine compartment are fully functioning in overkill mode.

For the cluster, I would think you could use one of the mounting screws for one of the gauges, solder your own right to the case, drill a new hole for a tiny sheet-metal screw, or just lay a wire under one of the mounting screws. Whatever floats your boat and you think is the most effective.

While you're at this (and with the key off of course!), pull the IVR off the back (one screw) and wire brush/sandpaper the area where it mounts. I've seen a LOT of rust under just that specific area, and it probably wreaks havoc on the circuit.

For the engine compartment, make sure you have the main ground cable to the engine block as close to the starter as reasonable, a fairly good sized (at least 12 ga) pigtail running from the battery straight to the body. Fender well is where Ford ran it. Add (if you haven't already) a strap or wire from the intake manifold to the firewall, and, while you're at it, throw one in there either between the engine block and the frame, or better yet, the battery and the frame.
I know it's overkill. That's why it's so important. Because "overkill" is just enough with a Bronco.

Paul