(52,429mi) Fun with a NEW TOY - The Sun Volts-Ampere Tester, Model C

In an effort to acquire temporally suitable equipment for my car, I have recently purchased (off eBay) a SUN Volt-Ampere Tester (VAT),  Model C.  I probably paid too much for it and still had to replace the lead wires.  Once replaced, the VAT worked  well, and I discovered just how well suited the tester was to my car.  The indicators were produced in 1948, a mere 3 years before.

Today, I test the circuit breaker on the generator-regulator.  At the same time I acquired the VAT, the instruction manual was also for sale at a nice low price.  (I discovered why the low price when I received a water-damaged book with black mold.  I scanned it and destroyed the original.)  The instructions for testing go like this:

Circuit Breaker

The following instruction may be used for testing the Auto-Lite three unit current and voltage regulator with the Sun Volts-Ampere Tester.

Be sure to operate the engine for at least fifteen minutes to normalize the regulator before any tests are made.
Note: In order to test the total output of the generator it is necessary to connect the terminal marked "F" to a good ground using the short jumper lead furnished with the Volts-Ampere Tester.

Stop the engine and disconnect the battery wire from the terminal marked "B."
Connect the negative black ammeter lead to the regulator terminal marked "B" or battery.

Connect the positive red ammeter lead to the battery wire removed from terminal "B" of the regulator.

Connect the negative black voltmeter lead to the generator terminal on the regulator marked "A."

Connect the red of the Voltmeter lead to the regulator base for a good ground.
Be sure the regulator is properly grounded through the dash and frame to the engine.

Start the engine running at idling speed and slowly increase the speed of the engine noting the voltage at which the circuit breaker points close.
On this regulator, the circuit breaker points should close between 6.4 and 6.6 volts. Note: Follow Auto-Lite specification for the regulator which you are testing.

Slowly decrease the speed of the engine and note the discharge current necessary to open the circuit breaker points.
The circuit breaker points should open between 4 and 6 amperes discharge.
If the circuit breaker does not open and close within these limits see Auto-Lite Specifications and procedure for making the necessary adjustments. 

I'm slow to learn things, so I try to understand why the instructions tell you to do certain things and what that means.  For instance, read the following:   "noting the voltage at which the circuit breaker points close."   I  had to go to my shop manual to find out that a circuit breaker point closing appears like.  "When the hand on the voltmeter kicks back slightly, it indicates points have closed. This should occur at 6.4 to 7.0 volts." p. 213, para.5.

Here are the results of the test:

The car was warmed up only 5 minutes.  The idle was a bit high.  However, it showed the above indications at the above settings.  The test setup was for the action of the circuit breaker.  Since the voltage did not go below 10.6 volts, I can assume that the test is not valid.  I believe that the grounding of the "F"removed the generator-regulator's ability to reduce the voltage to the appropriate range.  Therefore, next test, I will be sure that the car's idle is appropriate by first running it around the block for 15 minutes.  (When the car sits, I notice that it tends towards higher idling until well-warmed.)  Once the idle is normal, I will re-test the circuit breaker, first checking that the voltage is below 6.4 volts.  Otherwise, I will manually adjust the idle to a low setting and make the test.


In a future post, I will try to outline how the functionality of the generator-regulator produces these results.