FavoriteLoadingAdd to favorites

Stranger Than Fiction

Truth can be stranger than fiction. Recently, a regular long haul, over the road customer came in with a ’97 Freightliner and described a concern of “The trailer lights are acting goofy”. The description that the driver gave was that intermittently, different trailers would lose various lighting circuits. Three different trailers had exhibited similar symptoms. Intermittently, the trailers would lose clearance lights, or marker lights, or license plate lights and then randomly come back on.

A little history on this truck is that the owner/driver likes to do their own electrical repairs on the road. This has led us to multiple other electrical “gremlins”.  While a pocket knife and electrical tape can suffice for temporary emergency repairs, this should not be considered a permanent fix. To add insult to injury, the driver also brings a pet cat along on the road. Previously, while chasing electrical problems we found cat hair in the relay panel so thick that it was causing the relays to intermittently fail. Try to find that in any repair manual!

Obviously the problem had to be on the truck side. While on the road, the driver had the trailer plug on the truck replaced at one of the terminals that had a service center. Unfortunately, the new plug did not correct the concern. A few days later the condition returned.

When the truck and trailer arrived at our facility, our technician was dispatched with a description of the issues. He returned a short time later and stated that everything was working normally and there was no obvious problem found. We have had a customer that seems to make up reasons to come in, but typically, if a customer takes the time and trouble to bring something in, there is usually a real problem.

After discussion among the other techs, the general agreement was to verify a good ground and install an auxiliary ground if needed. Since the trailer was electrically grounded through the plug and all of the lighting systems shared a common ground, this seemed like the most logical place to start.

The technician next tested the connector ground at the plug and found a positive ground. He then removed the recently installed trailer plug connector to more closely inspect the rear of the plug. He found that several of the wires were partially pulled apart at the rear of the plug and that the cable was barely able to reach to the plug. Closer inspection found that the cable was not correctly routed which made it shorter than it should be.

After re-routing the cable, the technician performed our Preventive Maintenance Inspection (PMI) and noted that the left side sleeper shock absorber top bolt was missing and the shock was out of its mount. This condition caused the cab to roll even more than normal and increased the pull on an already short cable.

We replaced the missing sleeper shock absorber bolt and re-installed the shock. Correctly re-routing the trailer plug cable and securely fastening it should provide sufficient length to eliminate the pull concern at the rear of the plug when the cab rolls. The previous plug repair had not provided sufficient length of bare wire to properly install it in the plug and this also had to be corrected.

Lessons Learned?

First, just because you don’t find the problem quickly does not mean there is not a problem. No one brings a vehicle in because they have too much money and want to give you some.

Second, only repairing the connection at the plug would not have been a permanent fix. The next time the body roll was enough to pull the cable out of the plug the “goofy” light issue would have returned. The owner would have then had the same opinion about us as they have of the guy that replaced the first plug. Always look for the root cause of a failure. Replacing a blown fuse does not repair a short.

Third, be aware that a previous repair may not have been made to the same quality standard as yours. One of the questions we often ask customers when they bring a unit in is, “Has anyone else already worked on this?” If the answer is yes, get as much information as possible. If it was a “Do it yourselfer” then be prepared. Who knows what you’re going to find. If it was a professional shop, then with their permission, you might even want to talk with whoever did the work.

Lastly, if your shop is not doing Preventive Maintenance Inspections, you need to get on board. Would we have noticed the missing shock absorber bolt without the PMI? Possibly, but that would have been more by chance than design. Performing a Preventive Maintenance Inspection not only helps you to sell more services and provide a valuable service to your customers, but it can also help locate original causes of the customers concerns.

Article By: Bruce McDowell

Bruce is currently Service Advisor for Garber Diesel Service
Truck & Trailer Service Center

Bruce’s credentials include:  AMAM through AMI, ASE Certified Service Advisor, Ford Motor Company – Master Service Manager, Master Service Advisor, Master Parts Manager, Master Warranty Administrator plus 2 Management Degrees, Stationary Engineer License, and Retired Navy.   And above all… modest.