Wiring Diagrams Are Important In Diagnostics

Tom Owner/Technician Santaquin, Utah Posted   Latest  
Case Study
Electrical
Heavy Duty
2016 Freightliner 114SD 12.8L (DD13)—1FVMG3DVXGHHP6451
No Headlight Right Side

(in the field fleet truck for customer)

This style of truck was know for melting the plug socket at the headlight bulb. on this truck is was completely fine. started checking powers and ground there was no voltage. with out a wiring diagram visually trace wire back from hood to frame rail checking for damage or zip ties to cutting into loom. knowing left side works tracing voltage back to bulkhead control module left side firewall and identify fuses that power the circuits none off the fuses were bad still not having a wiring diagram to understand the simple headlight circuit high beam and low which is not the case now days. i have spent 2 hrs. and will not go any further with out a diagram. I inform the field manager that stated he has had to other mechanic look at this one and one stated the wiring diagram is not right. he forwarded it to my phone after seeing the diagram i was able to know where to proceed. at the chassis module repaired pin under cab by fuel tank, diag​.​net/file/fb2p0zj8g…

I found the problem and fixed it in 20 min.

+7
Helpful
Interesting
Conrad Owner
Aitkin, Minnesota
Conrad Default
 

Great job, it sure works, trying to find without can be miserable.

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Gail Technician
Raleigh, North Carolina
Gail Default
   

In these types of situations, I have worked on just about every type of wheeled vehicle but of course not this particular one, I have added a relay to a circuit like that. It's obviously pulling more amps thru that circuit than the connector can handle. Seperate that pin to a dedicated relay and eliminate the issue completely. YMMV Do you have a circuit tracer? When i was working on trash…

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Rex Technical Support Specialist
Alliance, Ohio
Rex Default
 

What make model worked best for you? I have the power probe and HF ones. Rarely use them because I usually have good SI and am mostly on the chassis side. The bodies i see are not nearly as complex as a packer. Mostly vans and dumps.

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Gail Technician
Raleigh, North Carolina
Gail Default
 

PowerProbe. I used the hell out of it on the packer beds. The shop was buying trucks at auction and refurbishing them. I did all the diag on electronics. Some of the PLC's were wired with all red wire. Sadistic. They started buying Navistar. What a clusterfawk that was. Everything was multiplexed. EVERYTHING. Didn't have diagrams. Yikes. Had to create control circuits (relays) for stuff like…

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Rex Technical Support Specialist
Alliance, Ohio
Rex Default
 

If you have not seen these they may help you with Navistar. I am very familiar with the Diamond Logic system. WO the diag software it would be a struggle even tho the codes can be read in the cluster. Main page bodybuilder​.​navistar​.​com/General/Home​.​H… circuit diagrams bodybuilder​.​navistar​.​com/General/BBcirc…

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Gail Technician
Raleigh, North Carolina
Gail Default
 

This kind of rings a bell. Think I found this back then. It was about 5 years ago. Bad case of CRS.

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Zachary Mobile Technician
Austin, Texas
Zachary Default
 

Rex thanks for the tip on Diamond Logic. I'm just beginning to learn how to navigate Navistar systems so any additional information is fantastic.

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Rex Technical Support Specialist
Alliance, Ohio
Rex Default
 

Tom, What was his source for the schematic? If it was NOT freightliner I would really appreciate knowing where it came from. Freightliner is very difficult to get SI from.

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Tom Owner/Technician
Santaquin, Utah
Tom Default
 

it was Mitchell 1

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