Generator Check

Bill Meyer, Fjordia, #393

If you're getting no charge, overcharging, or undercharging on your generator-equipped early model A4 (GEF 5001 12v usually), you can use this test to eliminate the generator as suspect:

1-remove drive belt and wires.

2-using a fully-charged battery, connect the FLD terminal on the generator to ground.

3-connect pos battery to ARM or GEN terminal on generator; there should be a spark and the unit should start motoring in the same direction as it does when in operation with the drive belt. It

should do this with no assistance. If it does not motor, or motors in the opposite direction, it must be repaired or replaced.

4-while the generator is motoring in the proper direction, remove the FLD ground wire; the generator should now motor FASTER. If it does, the generator is OK.


After motoring faster, it will stop after several seconds: it will not continue to motor

faster indefinitely. I and a guy at my favorite marine electric shop determined that

this was normal by repeating the test on generators known to be working.

On the GEF5001 generator, the ARM terminal is the one in-line with the ground-screw. The FLD is off to the side. Often they are not labeled.

If your generator plate has fallen off, there's a model number stamped into the housing at the same location. If your not sure what you have, take a photo and post it...I've got the Westerbeke book with

every model used on the A4 illustrated. The regulators are engineered specifically for use on certain units.

Don't forget to re-polarize the generator by applying a positive lead from the battery to the ARM terminal on the generator for a moment. Same can be accomplished by bridging the ARM and BATT

terminals on the regulator. There should be a spark. DO NOT TOUCH THE FLD TERMINAL WITH POSITIVE LEAD. Fry the regulator! Note from 1964 Chilton's re mechanical regulators:

"Most regulator troubles are caused by oxydized or burned or

current-limitng points. These points ...have a limited life span...

....Experience dictates that any malfunctions of the regulator are

best handled by renewing the entire unit."

After replacing my regulator with a solid-state unit on my generator equipped A4, I did long hours of monitoring the performance of the system with the engine running on a bench. At between 600 to 800 RPM, just above idle, the combo put out a steady 14.65V. At idle, 400 to 500 RPM, the output dropped to 13.60.

I let the engine run at idle for periods exceeding 20 minutes to see how much the battery would discharge, and found that there was no significant drop in static battery charge...still read 12.65 at rest. I'm using a quick-charge battery dedicated to engine starting. At 14.65V output, the generator will charge the battery fully in just several minutes. My lights and other electronics will be supplied by an independant deep-charge battery charged by a solar panel.

Generators are built like rocks, have no delicate electronics to fry, are available for a few bucks at consignment shops, and require only brushes( still available) every couple decades. Nice!

Neal at Obsolete Parts in Cincinnati, Ohio (phone number 513-731-4134) sells a solid-state regulator made specifically for the Autolite or Prestolite GEF5001 generator: $45. Got myself great and the whole unit is sealed in epoxy. Comes with nifty instruction on how to check your generator for proper function.