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Ford: light fuse..fuse blows..Wiring is clear..I drop automatic trans

Customer Question

Ford E250 backup light fuse blows. Wiring is clear to cable package drop behind driver/left (cut/tested). Soon as I drop automatic trans in R fuse goes. (day job electrician... just not today...)
Submitted: 5 years ago.
Category: Ford
Expert:  Ford expert replied 5 years ago.
Welcome to just answer.com. I'm here to help you and your 100% satisfaction is my goal. Unhook the trailer wiring if it is equipped with that and remove both back of light bulbs and tell me if the fuse still blows
Customer: replied 5 years ago.

Have already dropped main firewall connector + the three stacked modular connectors.

problem persists. Trailer lights factory. never used. blubs out. wiring disconnected to previous point mentioned. cut.

cut. snipped. whacked.

will go screw with the rear trailer hookup at rear/under... see if I can get them disconnected.

Expert:  Ford expert replied 5 years ago.
That would be the next place I would look
Customer: replied 5 years ago.

Both connectors D/c'd at rear.

Let's review.


firewall modular connector - disconnected.

3 modular (stacked) connectors - disconnected.

Backup lights feed wire (black w/trace red) CUT behind drivers seat high.

Reading to ground on feed wire going down/forward is .4 ohms (point four).

oh, and the two trailer hitch jack connectors are disconnected.



Expert:  Ford expert replied 5 years ago.
If the feed wire is shorted out to ground then the fuse would blow continually not just when you put it in reverse. It has to be somewhere after the reverse switch, using a test light or a known meter tell me which wire on the transmission range switch is shorted directly to ground with all the stuff disconnect
Customer: replied 5 years ago.

fuse would only blow when the feed wire is powered... like when you you put it in reverse.

fuse would not blow when not powered.

have to go to fire... back in a bit

and i just explain. exactly. where / what how....


Customer: replied 5 years ago.
Customer: replied 5 years ago.

Is the underside modular connector by the bell housing next?


Expert:  Ford expert replied 5 years ago.
Let me look and see what else is on that circuit which fuse number is it in which fuse box?
Customer: replied 5 years ago.

lookin for number... think it's "Aux Batt" (not installed) too.

12 (Twelve)

Back-up lamps, Auxiliary battery relay (gasoline engine only)


... only blows when placed in reverse... load side of trans sw...

if that's where they still put the reverse light switch.



Customer: replied 5 years ago.

fixed. not for nothin'. you want to send me $9.00 and I'll tell you what I found/did.


Bad Dog! No Cookie!


definition: expert. 'x' is an unknown factor and a spurt is a drip under pressure.

Expert:  Ford expert replied 5 years ago.

I had asked you which fuse box we are working in , if theres anything else i can do just let me know

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Category: Ford
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Experience:  30 yrs,experience shop owner,
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