How do I test an alternator with an external voltage regulator?

[ClydesdaleKevin]

Hey guys.  Another electrical question so I can get all my ducks in a row on Monday.  How does one go about testing a high output Lestek alternator with an external voltage regulator?

What kind of volts should I see coming out of the alternator before the regulator?  And what kind of volts should I see coming out of the regulator? 

If cleaning up all the grounds and connectors doesn't fix the dash gauge bobbing issue, then I'm beginning to suspect the voltage regulator itself, which has a separate "lamp" circuit...but of course I'll rule out the connections first, especially since a compatible replacement regulator from PennTex (Lestek is out of business) is close to 160.00 for the cheapest I've found them.

So yeah, how do I check an alternator for output when it has an external voltage regulator, and what kind of voltages should I be seeing at a given RPM? Both at the alternator, and at the regulator?

Thanks!

Kev

[gadgetman]

do a google search on how to full field that alt. They will tell you which wire to either full ground or full power  to full field the alt. Usually its a wire you ground. The alt outputs usually 14.5 volts when charging. All the regulator does is adjust the field coils of the alt so it charges a lot or a little.

so the first test is to full field the alt and see if it will charge, if it will the regulator is bad. If you are simply chasing a bouncing volt meter, hook a separate meter to the battery and see if it bounces too. If it does it most likely a regulator problem and long as the wiring going to it is ok.
IE no loose or corroded connections and no voltage drop on the batt pos lead to the regulator.

[ClydesdaleKevin]

Thanks G-Man!  I also contacted PennTex, who took over customer support for Lestek when they went out of business, and they sent me a PDF file of how to field test the Lestek alternator and voltage regulator, right down to wire colors and terminals, on both the alternator and regulator, with very clear voltage output guidelines...SWEET!  I'm going to try to upload it to the members resources area...not sure how to do that, but I'll give it a shot...lol!

The tech support guy at PennTex seems to think what I and everyone else thinks though, from my symptoms...and that is a bad ground or grounds somewhere.  So Monday I'm going to take every connection apart and clean them, every single one I can find.  (Gonna have to buy more dielectric grease since I'm almost out.)  At the alternator, at the engine ground strap, at every single ground wire I can find on the chassis, then I'm going to rewire the rats nest of trailer wiring, and see if that clears it up.  Then I'll run the alternator and regulator tests.  I think I'll run those tests even if the symptoms clear up just for peace of mind.  Gotta tell ya, as expensive as they are, if I ever have to replace the Lestek alternator or regulator, I'm definitely going to go with PennTex!  Outstanding customer service and technical support!  And made in the USA!

Okay...I'll mark this as solved if I actually solve it on Monday.

Kev

[ClydesdaleKevin]

Found the bad common ground and all the symptoms cleared up.  Tested the alternator and regulator anyhow, and they tested right in spec!  Problem solved, and the chassis electrical is now good to go!

Kev