'91 F350 7.3 idi Navistar engine. This morning, the WAIT TO START light wouldn't go off, but still started OK. I drove about 8 miles and shut off the engine. An hour later, the battery (ies) appeared dead, and I had to jump it off with my tractor. Now the tach spins wildly in both directions, the voltmeter gage swings from left last "0" to halfway and is jumping really fast. And, the anti lock brake light (which has been on at least 10 years) flashes off and on. The overdrive bypass switch also isn't working. When I shift into drive, there is a loud clunk, and it seems like the transmission is jumping in and out of gear while accelerating. I drove it 8 miles home like this.
So . . . which electrical circuit or component isn't working right anymore? Thanx in advance for all replies.

 

Sounds like your glow plug controller failed, and then you popped your alternator when you jumped it. Is your tractor a 24 volt system?

 

agreed. sounds like the glow plug relay stuck in the on position. then when you jumped it the alternator burned up. this probably burned out your glow plugs too.

 

Thanks guys. No, the tractor is 12 V. My tests indicate the controller as being one of the issues. The alternator is still putting out just under 14 V, but I have no way of checking the amp output. Looks like a trip to the local auto parts store for a load test. I charged the batteries & started the truck. But. . . you can watch the voltage drop with a voltmeter while running until the tach, etc. starts going crazy. I replaced the controller around 10~11 years ago, when I replaced all glow plugs (3 were bad that time).

 

Problem solved - you guys nailed it (as usual) A $20 salvage yard controller fixed it right up. Thanks to all.