Wiper Fuse intermittant problem

[HDRider]

My 1979 Tr7 has blown the wiper fuse a couple of times in the last month. This circuit also controls the brake lights and blinkers. My problem is I replace the fuse and can find no issues and then a couple of weeks later it pops again.

It does not seem to be tied to wiper/washer use so i am guessing that it is the brake/turn signal use that triggers this. I have looked at the wiring in the trunk and near the wiper motor and under the dash as well as the stop light switch but can see nothing obviously wrong.

I replaced the fuse again yesterday and cleaned all the light bulb bases in the trunk. So far it is working fine but I have only driven the car about 20 miles.

I am at a loss. Anyone have any experience or thoughts about this?

Edward Hamer
Petaluma CA

[dursleyman]

Could be a bad connection in the column switch or its wiring. Be worth checking it hasn't been damaged under the dash as well. The wiring on my car got damaged by the steering column top clamp bolt as it turned.

[FI Spyder]

A fuse blows if there is too much current flowing through it (excepting faulty fuse). This may be because a device is drawing too much current and the fuse rating isn't high enough. As a motor works (like a wiper motor) harder it will draw more current. I don't know if the fuse rating for the wiper motor is high enough for this eventuality but if the wipers aren't working when it blows, let's ignore this path. Increase in current will also happen if there is not enough resistance in a circuit. This will happen if a live wire wears through the insulation and contacts ground at that point. I would follow the live wire in that circuit that the fuse is in and check for worn or pinched wire such that the insulation id damaged allowing the contained wire to contact ground.

[HDRider]

I found the problem. It was caused by one of the support clips which hold the harness under the bottom edge of the dash.

The harness was inserted at an slight angle and the edge of the clip wore through the insulation over time. When the car twisted, such as crossing over the gutter a the edge of my driveway at an angle, the clip would contact one of the wires in the harness.

You can just barely see the clips if you remove the center cover on the dash and look under the forward edges towards the doors.

I just managed to get the clips out and lined them with some thin rubber gasket/sheet that I had in the garage.

It's been a week now and no more issues.

Edward Hamer
Petaluma CA