Tools & Tips
Best Practices in Wiring
Corrosion is a constant battle on buses in Michigan. Rust is not just body panels & entrance doors. This battle happens in your wiring. The following are some basic best practices for repairing & maintaining wires & connections.
Most fleets perform a chassis service & inspection ever 3000 to 5000 miles. This is the best time to inspect chassis harness routing for any rubbing or chafe points. Heavy starter & alternator cables are very important to check.
While you’re there, check any visible harness or module connections. Look for weather-pak/metri-pak seals that may be squeezed out at the connection. Look for any exposed pins that may have been pushed out of the back of an assembled connector. Both conditions let in moisture, salt & chloride that ruin the connector & create problems.
When repairing a connector, replace the pin with the right pin & seal for that wire & connector. This will ensure that the connector will remain free of moisture. Either you or Hoekstra can find these in the Freightliner PartsPro and Thomas’ Electronic Service Parts system. This gets you to the manufacturer of that connector and their part numbers for the pins & seals that you will need. Installing the wrong size pin or seal will guaranty another failure.
Once you have the new pin & seal installed on a wire & pushed into the connector, be sure to clean the connector with a contact cleaner like Dri by State Chemical. Place a film of dielectric grease to cover every pin in that connector. Don’t glop in the dielectric grease. Too much will push the pins out of the connector when you clip it back together.
Sometimes a wire will chafe & lose continuity. Another failure is corrosion or “green wire”. Back when salt was the Road Commission’s de-icing agent, green wire used to happen where the insulation was cut. Liquid chloride has changed these rules. The wire may not rot right where the insulation was cut. Liquid Chloride will travel inside the insulation to a low point in the harness & then begin to make your life miserable.
Don’t use butt connectors or scotch-locks to repair failed wires. Those unsealed connectors will continue to fail. Replace the failed wire with an overlay wire by installing pins & seals & using the same harness connectors & pin-outs that the failed wire used. If you must replace or splice in a short section of wire, be sure to solder the wires & use a quality sealed heat-shrink connector.
It is usually the best to keep your bus as close as possible to factory diagrams & installation. Given today’s school budgets, another guy may be deciphering your work 10-15 years later.
Resources
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