testing an alternator

[cherokeechief79]

sorry i know this has been covered and i did search but im still confused.
my aftermarket volt gage was bouncing rapidly since i got this project.
the lights would go dim at idle too.
with your advice we bought a new alternator and a new solid state voltage regulator.
neither fixed the problem but we didnt care as long as it was charging.
the other day the gage was reading a steady 11.5 while running.
we discovered that it was not charging and that was the batt voltage.
i want to "ground" the alt but im not sure which terminal to ground or if i should unplug the regulator first.
thanks

 

[MadScientistMat]

What year car is this? One or two field terminals on the alternator?

 

[413]

What year is the car?

Don't ground anything unless you know it's the right thing to do.

 

[cherokeechief79]

67 2 small wires one we have going right to an engine ground.

 

[MadScientistMat]

What sort of regulator are you using? The 1970 and up should have the other alternator field terminal wired to 12v power. But there are a few solid state replacements for the 1969 and earlier regulator too.

 

[cherokeechief79]

its from advance auto.it used to be the mechanical type but now its a solid state.
cant i just run a good ground to one of the spade terminals in back of the alt for a second and see if it starts charging at max?

 

[MadScientistMat]

Please post a picture of the regulator you have. If it was a direct replacement for your original, no.

 

[cherokeechief79]

 

[MadScientistMat]

For that one, to force the alternator to maximum output, connect the two wires together and bypass the unit.

 

[cherokeechief79]

so pull the 2 wires from the back of the alt and jump the two spade terminals on the back of the alt?

 

[MadScientistMat]

Pull the two spade terminals from the regulator and jump them together.

 

[cherokeechief79]

oh ok thanks ill have a voltmeter on the battery and see if it goes up to a high charge then right?
i know i should do this only momentarily for a test.

 

[MadScientistMat]

Yes. But you might want to take the alternator off the car and see if a local parts store can test it first.

 

[cherokeechief79]

the alternator is autozone but only a couple of mos old.
im thinking its a ground problem if i can trace it down.
it has 2 spade terminals on the back.
one i believe goes to the vr and the other we have just going to a ground on the engine.

 

[MadScientistMat]

the alternator is autozone but only a couple of mos old.
im thinking its a ground problem if i can trace it down.
it has 2 spade terminals on the back.
one i believe goes to the vr and the other we have just going to a ground on the engine.

That is correct when you have the 1969 and earlier regulator with an alternator with two field terminals. Just make sure the terminal connected to the regulator isn't internally grounded too.