Testing headlights

[Tapper02]

Is there any way to opcheck pedestal headlights when they aren't mounted?

-Tom

[PeteG]

I used a battery charger to check mine

[steve-0]

i think the blackout is 6 volt. its been a while since i worked on those.

[Tapper02]

I used a battery charger to check mine

Can you provide some details Pete?  I'd hate to hook something up wrong and blow a perfectly good headlight assembly!

Here are some pics of my assembly.  I just finished restoring it and everything inside looked fine...wiring, connectors, etc...including the bulbs.





-Tom

[Hadstock]

Not sure you can damage lamps that much, more likely to blow your power source with a short circuit if the insulation has rotted away. If you start at 6v, you should be able to see the main headlamp filament glow (if it's bright, it's a 6 v bulb). You do however need to clean all contacts - corrosion on contacts causes higher resistance, reduces voltage at the bulb and creates heat across the contacts, which can start fires under extreme cases (not too likely in this application though as I've only seen the results of plastic covered wiring or bulbholders starting fires when close to other combustibles). The old wiring I've torn out of my HT looked too corroded (even inside the insulation) to risk leaving and portions of an NOS harnesses I tested got hot very quickly, so I'm going with modern copper/plastic insulated wiring for the electrics.

That said, not sure you'll see too much in the dark with these anyway as the old tungsten bulbs aren't much of an improvement over candles !! These bulbs have relatively short lives and performance decreases over time as the filament deposits build up inside the glass bulb. This is one area I prefer to forego originality for illuminating the roadway with halogen sealed beams but that's just my personal preference. Not sure what sizes these are (mine has fender mounted headlamps) but automotive sealed beams ussually come in 5 3/4" and 7" options (older sources, such as those on e-bay, may well be the tungsten variety, so check what they're selling).

Phil.

[PeteG]

Hey Trapper, I used a 12 Volt 4amp trickle charger, I connected the ground lead (black) to the bare metal of the pedistal and then I clamped a screw in the hot lead (red) and touched the screw head to the contacts in the base of the pedistal, being careful not to touch the surrounding metal. I only held it there long enough to see the light glow and not long enough to get anything to hot.
The headlights, one with a Nov 1944, date still worked. I replaced the blackout bulb with a new bulb and cleaned up the corrosion. The black out lights didn't work when tested this way but after I took the assemblies apart I connected the hot clip of the charger to the bullet connector of the original wiring of the black out light and touched the ground lead to the blackout bulb socket and the light glowed. I think I have a ground problem in the blackout light housing, the socket is attached to the housing by a single rivet, I plan to drill out this rivet, clean up any corrosion and re-rivit it.
Also when I stripped off the layers paint I found stamps in yellow ink marked 12V on the head lamp and blackout lamp housings.
I used the charger because it was within arms reach when I was screwing with the lights one evening. You can do the same with a 12v battery by making 2 jumpers out of 14Ga wire and attaching alligator clips to each end.
I hope this helps, and can post pics if you think it may help.

[Tapper02]

I hope this helps, and can post pics if you think it may help.

Thanks Pete, that explains it pretty well.  I'll give it a shot and see what happens.

-Tom

[steve1973]

Tom,
If you are just wanting to see if the bulb is good all you have to do is check for continuity between one pin and the housing. Remember, one pin is for the marker light, one for the headlight or one for the blackout light (different pin location) and If it is good you hear the buzzer. If the bulb is bad, no buzzer. If you want to chect for brightness you need a 12 volt source for the headlight and a 6 volt source for the blackout light. I'm not sure what voltage the marker light is susposed to be. These are voltages for halftracks only. If your pedistal assembly was ment for another vehicle you will need to check the bulb for proper voltage markings.
Steve A.