Alternator charging problem

[stanz]

Recently upgraded my 68 Roadrunner for electronic system and replaced wiring harness, but I am having problems with the charging fluxuating with RPM's I mounted a new VR QS 8313 and replaced alternator with a Duralast DL75334 to increase amps, but cannot get it to stay steady. I was wondering how to make sure wiring is connected correctly, blue wire to positive side brush fld clip and green wire to the ground side fld clip? HUMMMMMM

 

[Don Frelier]

Both field terminals need to be isolated from ground with the solid state regulator you're using.

 

[dadsbee]

If they weren't he'd probably have smoked his harness already, but worth sticking a meter on to make sure...

 

[stanz]

Which wire goes where?

 

[dadsbee]

Which wire goes where?

It actually doesn't matter if they are both isolated from the case.

 

[stanz]

It actually doesn't matter if they are both isolated from the case.

But why does my voltage still goes up and down with my RPM's up to 13.5 when I raise over 2000 and 10 volts at idle 800 or so RPM's

 

[Don Frelier]

But why does my voltage still goes up and down with my RPM's up to 13.5 when I raise over 2000 and 10 volts at idle 800 or so RPM's

Do you have any big current draw items?
13.5v is pretty normal but 10v is low even at idle.
The alternator just can't produce enough for some reason. I'd be okay with 12.5-13.0 at idle.

You have a fully charged good battery?

 

[dadsbee]

10 volts sure sounds like a bad battery to me...

 

[stanz]

Battery fully charged that's what's the alternator output

 

[dadsbee]

If you're hooked to a good, fully charged battery... alternator is properly wired to said battery... there is no way you can read 10 volts unless you're running a LOT of electrical equipment you shouldn't be. As for the idle to higher rpm increase in output, that's how they work. Now there is a chance you have a bad diode in that alternator...

 

[Don Frelier]

What is the battery voltage with the car completely off? Should be around 12.7v