GP7 Headlight Circuit?

[Pat Masterson]

Our GP7 at FRRM has a headlight with no voltage on the wire. We could sure use a wiring diagram showing color codes,  resistor values, and dimmer switch components. Any kind of help would be appreciated. Thanks..

[Overmod]

This is a poster-child thread to be put on the RyPN Interchange.  He'll have PM documentation and probably some logical wiring improvements in short order... from actual Geep owners and restorers.  Meanwhile, since no one seems to be helping...

https://heritagerailalliance.wildapricot.org/resources/Documents/EMD%20Locomotive%20Specification%20Book%20GP7-SPEC8018A-30JNOV49.pdf

Nearest thing I have on short notice for a schematic is for the F9, but the codes might be common for some early Geep documentation  missing a 'key'.

https://heritagerailalliance.wildapricot.org/resources/Documents/EMD-WIRING-SCHEMATIC-F9-DB-PLATE-8845-01AUG1957.pdf

(Substitute 8825 for 8845 for the relevant Plate)

[7j43k]

If you go here:

http://www.rr-fallenflags.org

you can scroll down to:  "Operator/Service Manuals".  Clicking on it brings up a list.  There is one for a GP7 Manual, but it says the wiring diagram is missing.  But if you go to the GP9 Manual, click, go down to Section 5 ELECTRICAL EQUIPMENT.  Among other things, there's two wiring diagrams.

Seems to me tracing the wiring SHOULD be simple.  I don't know if the wires are color coded (you didn't clearly say) and/or if they're coded.

If you've got no voltage at the headlight, but you've got voltage outputting to the headlights, a broken wire/connection is likely.

 

 

Ed

[7j43k]

Hey Pat,

 

How's it going with your problem?  

 

Ed

[Overmod]

I came across PRR 7002 (the GP9) in an advanced state of 'casual disassembly' in Wilkes-Barre in the 1970s.  A great deal of wiring and relays was exposed to the weather, and I did not observe either color-coding or careful tagging or labeling of wire ends.  Apparently this locomotive was subsequently rebuilt into a Conrail GP10 and was extant at LTE as late as 2005, which I would never have predicted from its state when I saw it.