Voltage regulator?

[teuton]

Riddle me this. I have a 1974 Westfalia with a solid state aftermarket voltage regulator. The battery regularly becomes discharged to a point where the bus will not crank forcefully enough to start the engine.

I tested for short circuits or drains by disconnecting the negative battery cable and putting a voltmeter between the negative battery terminal and the disconnected cable end - no activity there.

I tested the continuity and resistance of the blue wire that goes from the dash generator light to the alternator. It seems ok.

I tested the alternator output by putting a voltmeter across the battery terminals while the engine was running and revved up to 2000 rpm or thereabout. It showed only 11.75 volts which was only .5 volts above where the battery was when I finally got the bus started.

I disconnected the voltage regulator and jumped the green wire (harness side) to the positive terminal of the battery. I started the bus and revved it and performed the same voltage test as above. Now the voltage read from 13.8 to 15.2 depending on rpm. I did this for only a few seconds as I did not want to burn out the alternator/wires/etc.

My question:

Does this absolutely indicate that the voltage regulator is bad or is there anything else that could be wrong?

[teuton]

Just for future reference, I will answer my own question.

No this does not absolutely indicate that the voltage regulator is bad.

In my case, I found that the two of the three small diodes inside the alternator were bad. They are called signal diodes. Their job is to give the voltage regulator a signal that will tell it how much voltage the alternator is putting out so that it can adjust it accordingly. They also go by another name but I cannot remember it at the moment.

Bad diodes can occur when the previous owner accidently connects the battery cables backward.

[keifernet]

diode failure can also be contirbuted to disconnecting the battery while the engine is running. this lazy mans method of checking the alternator does work ( if it does not die, it's putting out) but can cause great enough strain on the system to blow a diode.
this link is in reference to a marine application but applies to others as well.
http://www.diy-boat.com/Pages/search/search/tb_998.html

also see http://www.type2.com/library/electrip/aldiode.htm