1999 E-350 Super Duty (figured the problem would be the same for van/truck)

Problem: Backup lights don't turn on when in reverse.

Diagnosis: Changed the fused (because it was bad) but didn't fix it. The bulbs are both good. Brake lights, turn signals all work. I understand the backup lights are connected to the Neutral Sensor Switch. To test to see if the NSS was working, I put the van in Reverse and cranked... Van didn't crank (and likewise for D, 1-3).

So I guess the Neutral Sensor Switch works. The fuse works. The bulbs are good. Haynes doesn't have much as far as troubleshooting for this issue. Does anyone else have any suggestions? What should I look at from here?

 

If you have the 7 wire RV plug in the back, check for power when it's in reverse. The trailer plug and reverse lights are separate and in parallel. This will atleast tell you that the problem is isolate before or after the split.

 

I hooked up the voltmeter to the trailer plug and three of 7 wires showed power and that number doesn't change when in reverse... Still only 3.

Left light, right light and I think the 12 volt power indicate power.

In this diagram, I don't see a reverse terminal: http://www.farmbox.com/images/7WayTrailerEnd.jpg

Any other suggestions?

 

Did u ever figure out the problem? I'm in the same boat started with blown fuse??????

 

There are two fuses, one in cab, one under the hood, and both bulbs were bad. The perfect storm.

 

Hi new to here and hope to get help with a problem as I have not been able to find any help anywhere else on the web. Drive a 2012 f550 v10 gas flatbed tow truck with 86,000+ miles auto trans. about this time last year the back up lights and alarm started to come on when shifted in R then both would stop with in a few seconds, now they dont work at all. have checked the fuse and relay both good. since this have been made into a flatbed tow truck the back up lights in the wrecker's tail are LED. Have talked to the company that put the wrecker bed on it and was told that it is most likely a ford problem and not the wires leading from the cab to the tail. have looked on this site and other places on the web and have seen a couple post about the NSS but have been unable to find it in this truck, have looked under the truck along the tranny, under dash and pulled cover off steering and did not find it. I just tow cars I dont work on them so Im kinda out of my area but as I work for a small company with only 2 trucks right now and only mine running for the last 2 weeks we cant take it out of service to the ford dealer for even a couple hours. my boss is in now hurry to fix this problem again its been a year but its a safety issue and needs to be fixed before I or one other driver get stopped by motor carrier. any help to find out and\or rule out it being a ford probelm would be great. thanks for your time.
Jason

 

Is the fuse one the regular kind that blow and you have to replace or is it the kind that will either automatically or manually reset and work again?

The problem could be anywhere, from the reverse switch [which is either on/in the transmission or somewhere along the shift lever], to a wire rub/short issue to, a plug worked loose, to all the lights/alarm failing.

If it's a safety issue that you've had for a year, but the company is unwilling to forgoe any money to fix the problem, but would rather shaft the driver with fines, well, that's a dick move.

You could try to find a local mechanic who can look at it off and on, or you can google up on how to debug wiring problems.

 

I had this same problem on my 2005 f350 KR, the problem was the day/ night auto mirror..... I replaced fuses it worked fine, then it would go out... After numerous trips to a dealer, I got a tech that had worked on an f150 with same problem. It was the day night mirror, when head lights would shine on the mirror out would blow the fuse, they replaced the mirror and problem went away.