I recently repaired the pigtail going to a combo switch on the transmission of a 1978 Econoline camper van. The 4 wires were intermittently touching because the insulation had crumbled and disappeared near the connector. I have never seen plastic insulation deteriorate like that. The underbody is wide open. Could it be heat, or ozone, or what?

By the way, the resulting symptoms were horrendous. When 2 of the wires would touch the starter relay would get continuous power from the neutral safety switch line. It would touch the reversing lamp switch. Two starter relays and two starters burned up until I tracked this intermittent problem.


This is normal, the insulation has deteriorated due to a possible combination of things : heat, light, oil or petrol etc etc

It can be due to one or several of these factors.

When they designed the vehicle, it was designed to a price and one of the decisions was to use a wire with insulation to last a determined amount of time.

Given the age of your vehicle -41 years, the wiring is now past its best so you have to deal with that.

This means that you could completely rewire the vehicle which is possible, or you can repair as needed.

The risk if repairing as needed is that a future failure could cause a serious fire and you would have little left....

I have repaired wiring looms with serious fire damage and, seriously, you don’t want to go there.

If you want to extend the life of your vehicle then the first thing I suggest you do is contact the manufacturer to see if they have any replacement looms, you might be lucky. If not, you get to make one, or you pay a vehicle electrician to make one.

  • Aftermarket and accessory manufacturers may also offer replacement wiring looms. – DavidSupportsMonica Nov 16 '19 at 15:34

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