I'm trying to run the windshield washer bottle's pump.  Pulling the arm, I got 12 Volt reading but the motor won't run.  Took it out, tried it with a battery's power and it was running great.  Now, I can only think of that the 12 Volt I got is not powerful enough.  How do I measure if it has enough power?  And how am I going to improve on it?  Apparently not every 12 Volt is as powerful as the other.  
Not understanding it yet.
This is an '88 Vanagon, A/T.
The List is my only help, other than myself and the Vanagon Bible.
Zoltan