high voltage stock 6.1 alternator

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Buschi340

Buschi340

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anyone experiencing high voltage if running a stock 6.1 alternator with the oldschool external voltage Regulator? I measure 15V unloaded and 15.5V when headlights on. This is a little too much or? I am afraid of cooking my Batterie. I changed already the regulators ( same type ) but no change at all.
Any idea why the voltage is that high and how to drop this at least 1V?
 
I am not positive I have the right member but I believe it was Boden that has posted about this also. Don't remember what the solution was but I do believe it was figured out.
 
did a search, found a bunch. but all about frying Regulators or voltage up and downs. I have constant 15Volts. Maybe my Batterie is too small with 55AH which is also mounted in the trunk and grounded to the Chassis only? So light, fuel pump running drops Batterie voltage and the Regulator powers against that to charge the Batterie?
also read about a HP Regulator http://store.alternatorparts.com/partnoc8313.aspx

will try a bigger ( 72AH ) battery today and route a ground cable to the engine. will see what happens from there
 
Make sure you have a ground from the regulator to the chassis,and engine. Clean all paint and dirt from contact points.
 
Regulator is free of paint. I also soldered an extra ground wire on the regulator.
Did what I said above. Voltage dropped a bit to 14.8. But on 15.4 again as soon as I switch on lights. Or wipers..... funny is that I measure less voltage on the starter Relais than over the battery terminals. About 0.5v less... well, I am feeding the whole car from there.
 
From a glimpse at the wiring diagrams, i suspect that the PCM (powertrain control module) sends a PWM signal to the alt to control field excitation.
The old VR does something similar, it contains a transistor placed in series with the field winding in the alt, closing the circuit it to ground rapidly, much like a PWM signal.

It's setup at the factory, for a very old alternator and i think that's the problem.

What happens if you remove one of the wires from the field excitation winding?
Does the voltage drop to battery voltage?
 
you mean disconnecting one field wire? Isn't this terminating the regulating function and raises the voltage while engine running? I don't have a PCM, I have old School wiring..

my idea is sensing voltage close to the battery or start Relais ( both in the trunk ) but know i noticed i Need switched plus and not permanent plus like it is at the start Relais. I can only sense at the ignition Switch or fuse box ( which is now from a E30 BMW hahaha... bunch of obstacles )

Or last idea: It is simply the VR which is designed for 60A alternators and not the 190A HEMI sucker...
 
They adjust the voltage sensing with that potentiometer.
A wild guess would be, that this potentiometer could adjust the voltage "seen" by the VR,
basically "on"-time of the field excitation winding.

14.8V is not too far off a good charging voltage. You are shooting for 14.2 - 14.4 but i would say that 14.8 is acceptable.
 
14.8 Looks good yes. But this is in the car electric, junction Point at start Relais. The battery is receiving 15.5v same time. If lights on even more.

Anyway, it seems the Problem has been solved by itself this friday where i did a 150 mls trip to the drag Strip. Instrument at the das showed constant 14.2V. Guess that must be arround 14.8 at the battery if i still have this .5v drop...
 
Sounds like the cable to your trunk mounted battery is too small. What gauge cable are you running?? There should not be a 0.5V drop
Jim
 
That's too small.
For example: The Challengers wiring harness has a large 2/0 cable running from the trunk mounted battery to the front power distribution block (situated in the engine bay).
That's like 70mm². It definitely uses way more power than your project but i would at least double the size of that wire.
 
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