Backup light NG

[phoenix2013]

Had a correspondence form a customer. He's undoing a vast amount of wiring on a converted semi done by a DIY type who should have had someone else do it. No reverse lights with truck in reverse. He looked up my previous post where I identified the standard arrangement in the Delphi 280 flat connector (for a refresher), pin A Reverse, pin B Running lights, pin C Left Turn, pin D right turn, pin E Ground. 

He checked with a meter between ground and running light, +12VDC, he checked between ground and reverse, 0 VDC with truck in reverse. Any suggestions where he should go looking for the missing +12?

[Star Dreamer]

We tied into the reverse lights at the back of the truck and ran a line to the RV plug from there.

[rickeieio]

First thing I'd check is whether he's using led back-up lights, and whether the polarity is correct.  I bought Genuine Volvo cab clearance lights with the wiring colors reversed.  Right out of the plastic bag, and plug into original harness and no worky.  Scratched my head on that one for a bit.........

[Star Dreamer]

I should clarify that we have a Freightliner without any light control computer.

[phoenix2013]

I need to restate what his problem is more clearly. He is testing the flat plug in the back of the truck that comes from the cab (front of the truck), looking for ideas where that signal originates when you put it in reverse, (switch on a tranny, electrical junction box, LCM, fuse panel). I'm guessing here, anyone with experience looking for something like that?

[Wrknrvr]

  I would think of taking power from reverse light at back of truck and possible use a relay to power the light.

  Simple. I think it would work. And easy. Just put 12vdc to the relay use backup. 

  If original diy person cut backup wire off it should be in the wiring harness . Start at the back of the truck and look forwards.

 

  Just thinking Vern in a T-shirt 

  a tone generator maybe needed to trace it.

[noteven]

u tube reverse switch

 

Henry I believe there is a switch located on the shift tower of the transmission...

Edited May 15, 2021 by noteven

[rickeieio]

What kind of truck?  On our Volvo w/ Eaton tranny, there's a reverse switch screwed into the top rear of the tranny.  Ours failed.  Perhaps his did too.

[243 USA]

Thank you Henry for posting the question.

noteven and Rick it is my truck that Henry is asking the question for, it is a 2013 Volvo VNL 730 with and I-shift transmission. As Henry has stated my backup lights and the back up alarm on the truck do not work. The flat Delphi connector that has the reverse wire in it is showing 0 volts with a multi meter when the truck is running and transmission is in reverse. This Delphi connector is coming from the truck prior to my jackalopee.

Tomorrow morning I will check to see if there is a reverse switch on top of the tranny.

Thank you everyone who have posted.

[noteven]

Hi 243 - I am not familiar with the iShift - if you go on Volvo Trucks USA website and look in the “body builder” information - you may find wiring diagrams and related information. I believe they also have a phone number there to call.

Edited May 16, 2021 by noteven

[Darryl&Rita]

I thought I posted this earlier, but I don't see it now. I'd start at the reverse switch, confirming power in and out when in reverse. No power out? Replace switch. Power out? Follow the bundle, you've got an open circuit. No power in? Check fuse. Fuse good? Follow bundle, you've got an open circuit.

[noteven]

15 hours ago, Darryl&Rita said:

I thought I posted this earlier, but I don't see it now. I'd start at the reverse switch, confirming power in and out when in reverse. No power out? Replace switch. Power out? Follow the bundle, you've got an open circuit. No power in? Check fuse. Fuse good? Follow bundle, you've got an open circuit.

Darryl what do you think of those “cheaper” versions of Fox and Hound type circuit tracing tools available on line? If a guy is tracing 12v automotive wire harness troubles as in trailer running light short is there s specific type or model to buy vs the “ethernet” trace tools?

signed Still an Electric Dummy

[Darryl&Rita]

I haven't stayed on top testing equipment, or modern vehicles, so I'm not the expert. I try to limit my "experiences" to test lights and visual inspections. CanBus gets expensive if a guy isn't careful with testing equipment. My toning equipment was geared more to "Technician" grade, where reliability and ruggedness where requirements, not price point. For driveway use, something like this Canadian Tire tracer works good, but again, use caution when working on newer vehicles.

[noteven]

3 hours ago, Darryl&Rita said:

I haven't stayed on top testing equipment, or modern vehicles, so I'm not the expert. I try to limit my "experiences" to test lights and visual inspections. CanBus gets expensive if a guy isn't careful with testing equipment. My toning equipment was geared more to "Technician" grade, where reliability and ruggedness where requirements, not price point. For driveway use, something like this Canadian Tire tracer works good, but again, use caution when working on newer vehicles.

Thanks for the link - I think I will pick one up - 

I posted the nature of the problem in the Technical Tips section - turn signal mystery. 

Edited May 17, 2021 by noteven