Wiring Diagrams Are Important In Diagnostics
(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.