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Howdy Bolters,

Been driving my '46 1/2 ton quite a bit this summer. Come nightfall and time for headlights, I can barely see the gauges. The truck was converted to 12 volts and completely rewired with all new bulbs and such which has all been double checked. A fellow bolter I met at a local car show last weekend stated his gauge lighting was the same as mine, way to dim. Niether of us was sure where we got our 12v bulb swap info, here or Jim Carter or ??? .

So is it just a matter of finding brighter bulbs to replace the (I believe 3 candle power) bulbs in the cluster or does it have more to do with that little hood that covers most of the bulb when it's installed in the housing?

Thanks much,

Steve

Your truck is quite a bit older than I am used to working on, but in general, assuming that the headlight switch is working properly, one thing you might want to recheck is your grounding of the cluster. If the gauges in the cluster are working properly the cluster housing is well grounded, but you could still have bad grounding at the bulb sockets themselves. Because all the bulbs are affected, I would suggest checking the cluster grounding first and if the lights are still dim after confirming a good ground, check all the the sockets individually.

Mine are fairly decent. Now it's all new wiring and bulbs. And I checked the dimmer switch and it was nice and clean. A bad switch or wires could also cause this by causing excessive resistance.

When you turn the knob, does the brightness change at a steady pace? I don't know if the '46 headlight switch has a dimmer function like later models, but if it does, the element wire coils of the rheostat may be corroded. I have been able to clean dirty ones with an aerosol electric parts cleaning product.

Apply a direct 12V to the wire going to the dash lights. Bypass the headlight switch. You always isolate a suspected component to test. If they light good, it points to the rheostat and/or switch as suggested by Carl. If they don't shine any brighter, it points to the ground as Xena says.

We will take your word that you are positive they are 12V bulbs and that this is a fairly recent thing. Not, ever since 12V conversion.

Bulbs must have good ground contact inside socket, outside of socket needs good contact to dash holder/dash hole, dash holder to dash, dash to body, body to frame, frame to motor, motor to negative battery post.

Isolation meaning in this sense: nonparticipation in or withdrawal. Bypass it's function to isolate it as the bad actor.

My dash lights were doing the same thing, but are 6 volt. I found the rheostat part of the light switch was at fault. Simple solution was to take the dash light feed to a lug on the light switch that supplied full voltage to the dash lights. No problems in the past 4 years or so and that includes some pretty long (as in many hours) night drives.

GoodLuck, RonR

Maybe your instrument cluster is of similar design to the one in my 38 Master. In my case, a way of improving the lighting was to take the cluster apart and spray the inside with white paint. This is a well known procedure for the 38 Chev Masters. I understand there are much brighter bulbs available too but I haven't tried them.

Thanks for all the replies. It's not power or ground issue, all that was double checked including running a separate ground wire and hooking the positive wire straight to the headlight switch feed. If I pull the bulbs (Wagner 1895's) and power them up they look bright enough to do the job.

I think Trukernix is on the path I am leaning towards but since I've no previous experience with these trucks I'm not sure if it is a known problem. Any other ideas?

I used the white paint like truckernix with my gauges. White appliance enamel works great for me.

Thanks Alvin, I'll give that a go this weekend. I ordered up some LED bulbs that are twice as bright as the incandescent bulbs so we'll see how that goes. Worse case is they wind up too bright and I put the dimmer to use.

On another note, I just realized I confused the issue by posting in the Electrical Bay instead of the intended General Truck Talk section. Mea Culpa!

Steve

Steve,

12v or 6v system, and LED voltage to match?

Dimmable LED?

Why would you think a question involving lights/wiring would not go in the Electrical Bay Forum?
Had you posted it in General Truck Talk it would have been moved here.

Holy Cats, what a difference a coat of white paint makes!

The back of the bucket originally was painted white (still looked reasonable) and the top 3/4" was painted black. Painted all that white as well as the three gauge mounting plates and inside the bulb shrouds. The back of the cluster face plate was galvanized, starting to gray but not too bad. It had three areas of black paint which I assume is to cut glare so I masked the black and painted the rest white. Literally a night and day difference.

TC,
12 volt dimmable bulbs, I'll report on those when they get here. If I hadn't ordered them before the painting, I wouldn't bother at this point but maybe I can claim the $13 on my taxes as an education expense.

Steve

If I was doing it over again I would put white enamel on all the gauge needles. I won't take it apart now just for that!

I sprayed my needles with the Rustoleum color "Canvas". It's about half way between white and the original tan, way brighter but looks original to the untrained eye.

The LED bulbs came in yesterday, I sourced them from a company online called superbrightleds.com. I purchased a BA9S-W4-32-12VAC for the high beam indicator and it is much brighter than the original, very happy with that. The BA9S-WWHP5 bulbs that I got for the cluster lights and the dash light above the key switch are little flame throwers, but they are too long to fit. That's my fault as I was going for the big bad boy brightest thing they had and didn't double check the length.