With 15v output, there’s nothing wrong with the alternator, the regulator is the problem. You’ve still got some life in those brushes.
+1With 15v output, there’s nothing wrong with the alternator, the regulator is the problem. You’ve still got some life in those brushes.
Yes. Factory gauge.Are you using the factory gauge on the truck? Using those gauges for anything is worthless
Mine reads anywhere from 9-13v on the factory gauge depending on how its feeling, yet the truck is consistently at 14v when measured. I put a $10 USB charger with a voltage readout in my cigarette lighter so I can keep an eye on it.
I was looking at the wiring diagrams... The regulator has a three pin connector, pins labeled "A", "S", and "I".
A is the power to the armature. It is connected to the main battery buss, same as the main alternator output. The regulator will gate current from this line through the brushes and energize the armature rotor winding to create it's magnetic field should this voltage be less than 14 volts or so. Set by design. This voltage is referenced to the alternator frame ground. Armature current is also returned to the alternator frame ground.
Should the connection to A be open, there will be no armature drive current available, no magnetic field, no output.
However, should that connection be lossy, and you are losing, say, 4 volts across a corroded connection, the regulator will call for more and more voltage, increasing armature drive current, until it sees the 14 volts it's looking for. But the alternator is actually putting out 18 volts to get that 14 volts at the regulator sense point.
The S terminal is an alternator sense point. It's connected to one of the three legs of raw three phase AC power coming from the stator winding. It let's the regulator know the alternator is turning.
It's that wire that loops from the regulator connector right back to a single small connector pin on the main alternator body.
Not much sense giving armature current to an alternator that's not spinning. All that will do is drain the battery.
The I terminal just drives an indicator lamp if something's wrong, by pulling the line to ground.
I note you have already looked carefully at the grounding...which is probably the most common gremlin in the fray.
Hope this gives you a little more info to work with.
At this point, I agree that you have a bad voltage regulator, with my belief that inside it is a shorted pass transistor for armature field current.
Would be great upgrade from his current 3G alternator.When you get the issues settled I suggest a 3G alternator. It is a bolt on replacement. You can connect it as sorta one wire, or with two wires you can have a light.
Would be great upgrade from his current 3G alternator.
Touching that F terminal to ground should turn the alternator full ON. Typically used for seeing if a dead regulator or a dead alternator is the culprit of a no-charge situation. I am pretty damm sure your alternator is fine.When you do the tests, where you touch the "F" terminal for ground,
Yes. Full battery voltage at each of the two screws, with the engine off.Touching that F terminal to ground should turn the alternator full ON. Typically used for seeing if a dead regulator or a dead alternator is the culprit of a no-charge situation. I am pretty damm sure your alternator is fine.
Since you've made a nice test point there, measure the voltage from the F terminal to ground. It oughta go to battery voltage if the engine is OFF. Upon engine start, it should drop LOW until battery buss voltage gets up to 14V, then start rising as the regulator starts throttling the alternator back down.
With the engine OFF, do you have battery voltage at BOTH the F and A screw?