My 77 has 12.6 volts at the battery but less than 12 everywhere else in the truck. Is there a tranisistor or resistor, etc. that I Should be looking for as the problem?

 

That just means that resistance in your wiring harness is dropping the voltage down from the source. Is this 12 with the engine running or with it shut off? With the engine running, you should still see around 12 at minimum with all the accessories on - headlights, wipers, blower motor. That is when the load is at its heaviest. Voltage will drop slightly when the truck is in gear because the alternator is turning slower and cutting the field less.

Whether or not your numbers are good really depends on whether or not you had the motor running and what electrical loads you had on the system. If you want you can start tracing your wiring harness from the battery and look for frays, etc that would contribute resistance that drops down the voltage for a given current. If your truck was off and you read 12.6 at the battery and read slightly below 12 at the tail lights with all the lights on then that is plenty reasonable. If your truck was running and you had the lights on and you checked the voltage at the tail lights then less than 12 would be a tad bit low. You can only get a voltage drop if a current is flowing.

By the way, the only transistors that you'd see on a 77 would be in the Duraspark box and the radio if so equipped; and maybe the cruise control amplfier if you have that. There are no circuit elements in the mainstream harness, expect for a specially doped wire for the coil. It's simply for power transmission. Nothing but thick wire and simple switches from front to back.

 

If you have EVERYTHING on you might be at 12v. Just idling with not much load, you should have in the neighborhood of 14 volts.

 

What I spoke of was while not running. While running at idle, I have nearly 14 volts at the battery without the accessories turned on. I also have not checked the votage anywhere but at the battery while running. I will chase through as suggested and check the values.


Thanks!

 

Ford put the least amount of copper in the wiring as possible. So you will get some voltage drop through the factory wiring, as it's barely big enough to carry the factory elec. loads of the truck.