Monday, June 08, 2015

Mechanics and Corrosion

The most difficult job when finding an electrical fault is when corrosion is involved. It's hiding somewhere in a connector or poking through the wiring insulation.

So what is the best way to troubleshoot corrosion in the electrical system? One way is to search and destroy the problem by opening the loom and exposing the green stuff but that is frustrating and  takes a lot of time. However it's necessary to make a proper repair.

Another method (when you know which circuit is faulty) would be to check for voltage drop in the circuit that is not functioning. If you can hook up a volt meter at each end of the circuit and see if there is a loss of voltage when the circuit is energized then you can be assured it's a bad wire. Checking the resistance is another check that works.

In our shop we've been using a load on the wiring circuit in question. A regular light bulb (non LED) hooked up to the one end of the wire will tell you if there is a lack of current when the light is dim after energizing with battery power. The wiring is either corroded or frayed restricting current flow.

If you have money to spend on tools you could use "diamond logic builder" software for International trucks to see the circuits working in a graphic form on a laptop. You can click on a circuit and actually see if the load is getting battery power. The pin outs on all the connectors are at your fingertips. I've used this software and it's a great tool to have compared to digging through wiring harnesses with a hope and a prayer.  


John B. said...

Morning Sir.I love your Blog site....I am a Auto Mechanic. I just purchased a 1997 Thomas pusher with 8.3 Cummins and an Allison 6 speed. I drove it home 380 miles with absolutely no issues in May of this year. I have repurposed it to move rescue dogs and Cats. So it has all seats removed, and shelf units added. Plus I put a Genset in the Cargo box, and Ran Power up into the Bus cab to Run 3 AC units on the Roof, as well as 110 power along one wall at roof level. We were super careful to not run any screws into existing Wiring areas for the Bus. and all of the AC and 110 Power is run thru conduit mounted to the Ceiling. That being said.
I now have a Heat gremlin. When I start the Bus and Run it for somewhere between 20-30 mins at Idle or Driving speed. All the Continuous Duty 150 amp solenoids get HOT to the touch enough so, that you cannot touch them. and the biggest kicker, the Fuel shut off solenoid kicks Fuel off.
I bought a new fuel shut off solenoid thinking it was at fault, but same issue with new unit. My question for you is, have you ever run into a Heat issue with these Duty solenoids, and if So what might the Cure be..? you are welcome to call me if more info is needed....Many thanks From Oregon. John. 541-232-9958

John Whelan said...

Those solenoids generally run hot at all times. The fuel solenoid gets hot as well. I'm thinking there's isn't enough voltage to keep it engaged. Check for run voltage to the solenoid should be same as battery voltage.