69 Charging System Diagnostic/Check - Alternator Voltage Regulator Not Charging

[Johnnys440Charger]

When I remove the positive battery cable from the battery, the engine shuts off.  Is there any step by step instructions posted on this site to diagnose my charging system?

I have a 2 FLD Alternator (only 1 FLD connected) with an mechantical electromagnetic Voltage Regulator.

[Nacho-RT74]

need grounded the non wired brush, that's the reason... alt is being feeded just by positive coming from reg and negative is isolated. Need both to create magnetic field

wire the other prong or simply replace the isolator washer of brush for a metalic one. That will ground

[Johnnys440Charger]

Is this silver screw internally grounded?

[Nacho-RT74]

does look it is already grounded... yeah the screw fits on housing internally and once fit and makes contact with brush prong, then makes ground the brush.

does look the isolator was also cut on hole to make the screw gets the prong and then ground. I would simply use a metalic washer replacing the iso washer to keep safe the isolator. Just in case make an electronic upgrade later. Anyway with replace the isolator and brush will be enough to get it back!

[Johnnys440Charger]

With engine off, battery has 12.6 Volts.

I disconnected the positive + FLD wire from the Alternator.
Then started the engine, and connected a wire from the positive FLD to the positive battery cable terminal.  Battery voltage read 14.5 
While the engine was running, I removed the positive battery terminal off the battery post and the engine kept running!    

That means the alternator is good and charging 

I'm guessing bad voltmeter, bad wires, or ground.   I'll troubleshoot somemore.  Keep ya'll posted.

[John_Kunkel]

Removing the battery cable with the engine running can be risky, when you do this the alternator has no battery voltage to compare its charge to and the resulting voltage spike can fry some components.

[Plumcrazy]

Removing the battery cable with the engine running can be risky, when you do this the alternator has no battery voltage to compare its charge to and the resulting voltage spike can fry some components.

  That's not a good way to check to see if the alternator is charging.

[mopar0166]

need grounded the non wired brush, that's the reason... alt is being feeded just by positive coming from reg and negative is isolated. Need both to create magnetic field

wire the other prong or simply replace the isolator washer of brush for a metalic one. That will ground

Im in a simular postion right now, and i dont use the second field. where can you ground it too or should i just use the ground screw slot that is on the back?

[Nacho-RT74]

if you have a round back alt, yes probably you have one of the laters produced with options to both systems ( lates 69 and 70 ). the CORRECT way to get the field brush grounded is get the propper brush without isolator used on earliers and mount on the right spot.

Note...the pictured alt is a squareback alt and ground the brush is the only way to make it wrok on earlier single wired brush, they don't have the grounded brush spot.

If the alt doesn't provide the ground brush spot, then replace the isolation washer and replace with a metallic washer on any of the brushes ( better the one ilustrated ) and to safety from wrong wire the brush, cut the grounded prong.



you could also simply wire ground one of the brushes, but IMHO, that looks some goofy.

[2Gunz]

Just a note here if you have a Voltmeter its not necessary to remove the terminal from the battery to see if its working.

A good charged battery will read around 12.5 ish volts.

If the alternator is working the battery should read more than 13.5 and less than 15.



And if you dont have a voltmeter you should really invest in one.

They are cheap, and if you know how to use it can save hours and hours of time.