Generator

Many thanks, We are still trying and will let you know the outcome.

Thanks Again, John

I hope it's not too hard to get to the bottom of it!Since you're still working, I'll add in a couple pieces of information just in case they're helpful.

1. If you have a bad voltage regulator (my plane did when I bought it) instead of putting in another antique Delco-Remy unit, I went with the solid-state electronic  PMA replacement . It's lighter, has no moving parts, and basically does everything better, including a "soft start" to save wear on the generator, and it can automatically flash the field when needed.

The only downside is that although it mounts to the same holes in the same location, you need to buy mounting bolts that are about 1/4" shorter (or stack up a bunch of washers... ugly!) because the base flange is thinner. The original voltage regulator mounting bolts will "bottom out" their threads before they tighten down on the new unit.

2. If your master switch is faulty or intermittent, a new high-current switch is too expensive, and the old kinda-high-current switch is, I believe, only available in new OLD stock or used. I still don't trust them. The Alpha Aviation STC is $300 and comes with all the parts needed... it removes the high current from the switch - now the switch only carries 0.8 amps to activate the solenoid, and the solenoid does the "heavy lifting" of feeding many amps to the starter.

Compared to my previous drawing, the solenoid STC changes your wiring to this: 

  

(There's also a voltage spike protection diode in the STC kit, I just didn't draw it)

Still investigating. We are doing the annual right now and trying to determine exactly where the problem lies. Thanks for your assistance, I will keep you informed of our progress.

Any update? Curious about the source of this problem.

Thanks, We will give it a try!

John, you can diagnose whether the generator is defective by *temporarily* attaching a jumper from the "F" (field) stud on the generator to a good grounding point on the engine or airframe.

If you don't have a voltmeter on your instrument panel, you need either (a) one that either plugs into the cigarette lighter outlet, or (b) a handheld voltmeter/multimeter attached somewhere on the bus or battery to show the voltage in real time.

When the "F" stud is grounded, you're forcing the generator into full output. (The voltage regulator normally controls this) so when you start the engine with the "F" stud grounded, if you raise the RPM too much you will have an overvoltage event!

The test procedure is... remove fuses or pull breakers on all radios, transponders, and other avionics. You only need the starter, battery, ammeter, and voltmeter for this. Now, start the engine and keep watching the voltage. As you increase RPMs, the voltage will rise unless the generator is defective. The ammeter will also swing to the positive "charging" indication. Don't throttle up past 14.5 volts!

If the generator is good, then you either have a bad regulator or a broken wire. The wiring is pretty simple, so you should be able to trace it all out. It's not unusual to find frayed wires or corroded end connectors, so don't trust a wire you haven't fully examined even if a voltmeter finds continuity.

IMPORTANT NOTE: The master switch in the Ercoupe is handling a lot of amps every time you use the starter... more amps than that switch was designed for. It's a 2-pole switch so it's possible that the pole carrying the "F" field voltage has failed, even though the other pole is allowing the starter to energize. Be suspicious of this switch! The Alpha Aviation STC that removes the high-amp load from this switch is a great investment.