Volkswagen Repair: 86 vw cabriolet power drain, field windings, vw cabriolet


Question
I have an 1986 vw cabriolet. When I start the car the battery meter shows a large drain. I have tested the alternator and voltage regulator by using a voltmeter to test the voltage across my postive and negative terminals of the battery. That test indicated a reading of 14v which is within the 13.5-14.5v range for a correct operating alternator/v reg.  Secondly I checked for current drain by using an ammeter and checking for drain across my negative ground post and the cable and got nothing...well (-.01).  The drain still persists...Any suggestions you have would be greatly appreciated.

Answer
OK Rob;
So let me understand completely.  You did a "parasitic drain test," by placing the DVOM in series with the cars' electrical system.  You disconnected the battery, and placed on lead on the battery terminal, and the other lead on the cable end.  Right?
If there is only a 0.01 Amp draw, then there isn't a parasitic drain.  The battery is either old and in need of replacement, or the alternator is not able to provide enough current to keep the battery charged.
A load test of the battery needs to be conducted.  You need a large load that you can control, like a "carbon pile resistor" to load the battery for about 30 seconds at half the rated CCA of the battery you are testing.  Immediately after that you need to measure the voltage of the battery, and if it is less than 10.5 volts after the test, the battery is no good.  By the same token you need to examine the current, or Amperes the alternator can produce, and that is a little harder to do without a specific tester.  Take the alternator out of the car, and take it to a local parts store that offers free testing of these components.  They will be able to energize the "field" windings so the alternator puts out its' capacity, if it is too low the alternator can't keep up with the battery drain, and you park your car, and it won't start again.  That's pretty much it.  I'd say it's one or the other.