Most Flight Engineer stories begin, "There we were, flying along all fat dumb and happy, when [insert problem or near-death experience]..."
Well, there I was driving along the highway all fat dumb and happy when the wipers and gauges quit. I was creeping in traffic at the time and didn't notice right way that the transmission was also in limp-mode. This happened 100 yards past the last exit for many miles, so when traffic speed picked back up I was an obstacle.
There was also a clicking up under the dash, coinciding with a momentary pop in the gauges, telling me an automatic circuit breaker was attempting to re-power things, but was finding a short circuit somewhere and kicking it all back off. This cycled every few seconds continually while I was trying to find a place to pull off.
Shout-out and many thanks to RWH for talking me though where to look for possible shorts. Everything was visually good, I couldn't see anything unusual or any wire bundles touching anything they shouldn't be. I attempted to plot a non-highway route home in limp-mode but on Steven's advice decided that wasn't such a great plan with an unknown active short in the electrics. Called the tow truck...
Yesterday was solid rain so nothing got done. SpankyBear suggested it might be an issue with my security key switch (NOT a keyed switch - just a separate switch that interrupts the neutral/park safety line) so this morning that was my first troubleshooting - put the start circuit back to OEM. No change...
Troubleshooting 101 asks; what made this trip different or unique from any other trip? Well, to start it was a lot of 70MPH until the traffic jam when the short occurred, and the wipers had been on longer than they ever had since I got the truck. I've only ever used them for a few minutes here and there, but never for 20 minutes nonstop. So that was my second check - unplug the wiper switch and see if the auto-c/b would stop cycling.
Unplugged the wiper switch and the truck returned to normal. Fired up the truck and was relieved the start box hadn't soiled the sheets - the glow plugs worked as normal and the truck started. Wish I had thought of that before calling the tow!
I put the meter on both connectors inside the wiper switch plug to see if there was continuity between either wire and ground, and there was not. That should rule out the wires shorting at the base of the A-pillar (thanks Steven!) and narrow it down to the wiper switch or wiper motor.
So with the motor running I unplugged the wire between the top of the switch and the motor, and plugged the switch back in at the bottom - no change. Hated to risk it, but wanted to be sure, so attempted to plug the motor back in and the gauges died, and an aromatic curl of smoke came from the plug. Left it unplugged and restarted no problem.
Took it around the block and it's shifting normally again.
I'm going to say the motor is shorted internally and start looking for another. Even though the wiper switch was off, the blades were likely still trying to park themselves, so the motor was shorting and kicking the c/b off. If I had figured that out I could have pulled the plug to the switch and drove it home on the highway. Expensive lesson.
