[Alvin]

FWIW: I had a similar problem in the early 80’s with the 1st 78 TA I owned.

Car was all original, 400 Auto, Pwr Windows, Cruise, with factory wiring harness. It ran flawlessly for years and suddenly –one day - the electrical system gremlins said hello.

Symptoms: At a standstill with the Tach pegging, Gauges inop, etc. at engine start up, once or twice, just like yours. Then after turning the engine on and off, it returned to normal operation.

A few days later while driving on the interstate, same thing happened; Tach pegged, gauges inop, etc. then back to normal. The engine never missed a beat, continued to run fine. I realized that this was occurring as I was driving over a gradual up and down section on the road way. Once I got to my destination, opened the hood looking for the obvious…and nothing! At first. Then…

I got lucky: After feeling around the engine wiring harnesses with my hands for any “Hot to the touch” electrical wiring, I discovered that the positive battery cable was very hot to the touch, and there was a slight smell of burnt insulation. With the key in the on position I would get the same gauge problems. The alarm screeching on my radar detector plugged into the cig lighter made the diagnosis easier from outside the car.

Conclusion: The positive battery cables insulation was laying on the sharp edge of the upper control arm and had rubbed a hole through the insulation of the positive battery cable. The cable was an aftermarket replacement, which was longer than the original. Each and every time the suspension flexed, the control arm moved and the positive cable would go to direct ground and cause the same problems you experienced.

Hope this helps you. I suggest you keep it simple, and look for the suggestions posted earlier, such as bad grounds, etc. No doubt there will be other “experts” here who will tell you what is really wrong with your car! LOL!!!!

Another simple ground problem: The only other electrical issue I had was when the dome light switch on the drivers’ side got slightly corroded on the threaded ground where the switch screws into the door jamb. This is a single wire positive wire switch grounded to the body. When parked on an incline, passenger side lower than the driver side, the dome light would come on with a dim brightness (due to bad ground and body flexed on the incline allowed slight movement of the drivers’ door).

Simple Fix: Removed switch (drivers side was problem), wire brushed and cleaned threads on switch and door jamb ground threads. Once clean, I used di-electric grease on the switch threads and door jamb. Problem solved.