Railfan Technology > locomotive headlight switch

What voltage would a diesel locomotive headlight switch operate on? I've seen two on ebay that were removed from a scrapped locomotive.

Most likely  75 volts. Then again newer locomotives may have different wiring and voltages, dim, medium and bright positions on the switch..  All depends on what type of switch and the age of the locomotive.   Doug



Edited 1 time(s). Last edit at 12/17/15 19:21 by hoggerdoug.

Until the ditch light era, all locomotive headlights were bright on 32 volts.
Medium and dim just added resistors in the circuit, medium was about 28 Volts.
​Ditch lights are always 75 Volts.
​The new units have 74 Volt headlight bulbs, but still have to use 32 Volts in the control wires so they will still MU with older units.
G

The switch I've seen has Off, Dim, Med, and Bright and is marked as a front headlight switch . I know this sounds a bit laughable, but could the switch be made to operate with fog lamps on a truck, or is it only able to operate at a setting no lower than 32 volts?

A switch works fine on any voltage that doesn't exceed its maximum rating.  A locomotive switch would work just fine with automotive lights.  It will not dim the lights without external circuitry, but it would easily do on/off duty.

Most locomotives use the 74VDC bulbs nowadays, but you will still see some older power (on CSX, it's usually 4-axle Geeps) with the 32V bulbs...IT's really only an issue when a bulb goes out and you need to replace it...putting a 32v bulb in the 74v system makes for a VERY short life of the bulb(about 10 minutes followed by a nice camera flash strobe).
EMD had an option for3 position lights...Off, medium, and bright.  I've seen this on the newer SD70Aces for UP and KCS, as well as on a fleet of PennCentral purchased (then Conrail) GP38-2's.  The 4 position light switches are prefered by engineers, since Medium when we meet trains is still bright enough to blind an oncoming crew...

radar Wrote:
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> A switch works fine on any voltage that doesn't
> exceed its maximum rating.  A locomotive switch
> would work just fine with automotive lights.  It
> will not dim the lights without external
> circuitry, but it would easily do on/off duty.


Shouldn't be a problem with external circuitry. There's a place here in Columbus Ga. where I live that only works on the electrical systems of cars, trucks and I've even seen pumpers for the fire dept. having work done. I'm pretty sure they could rig it up to work on all four settings.....however, the REAL question is, does the switch still work?  It's old. It was removed from a unit that was scrapped and if I had to say it most likely came from an EMD locomotive by the looks of it.

Standard locomotive control voltage is 75 volts. Anything less such as bulbs is reduced with resistors or transformers.
RWJ

apollo17 Wrote:
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> What voltage would a diesel locomotive headlight
> switch operate on? I've seen two on ebay that were
> removed from a scrapped locomotive.