Last week, I found my right engine alternator belt shredded in the bottom of the engine cowling (due to a frozen idler pulley .. another matter). During the just ended flight, I had no idea I had lost an alternator.

According to the PA30 Maint Manual, Figure 11-68a, the outputs of the Left and Right alternators connect to a common buss bar after passing through their respective 90 amp breakers.

My question is this: does anyone have a way of connecting some sort of indicator (lights?) to the respective alternators such that they will indicate an INDIVIDUAL alternator is outputting current (or not outputting current .. either way will do)?

Unfortunately, our L/R push button ammeter doesn't have a built-in indicator like our vacuum gauge does. I have a voltage monitor on my JPI Engine Monitor, but it only indicates buss voltage.

Frank,

Piper built a kit for PA39s which is real close to a 30C and put it in the 39-142 and up Twins. Clifton Aero told me about it and I put it in a couple of years ago as we once had BOTH alternators fail on an IFR flight ... and lived to tell about it. I don't have the information with me but could tell you more in early April if no one else responds.

Each alternator lights a red light button if inop or RPM under 750-1000.

Thanks, Pat. I'll give Clifton a call.

fRANK,
THE PLANE POWER ALTERNATOR KIT HAS AUTO PARALLING WITH l/r ALT. FAIL LIGHTS FOR DISPLAY ON THE PANEL.
STEEN

Hi Pat,

I talked with Clifton Aero, and he remembers installing your kit. He referred me to the PA30/39 Parts manual for the kit number (which is 760-744).

In reviewing the Maint Manual (Fig 11-68b on page 3F23-24), I found the schematic for the installation in the later model PA39.

HOWEVER, this system is for a PARALLELING alternator system, and the alternators have an additional output marked AUX. It is the signal from this output that triggers the INOP lights. Is your PA39 use the paralleling system? Mine is a NON-paralleling system, and according to the schematics, uses a different alternator.

Any thoughts?

Frank - our alternator is Alternator MAA Prestolite ALX-8421 GF000030, is yours the same?

Frank,

I have a PA-30C. The factory system is extremely problematic because of the single regulator which means that a fault in one alternator is likely to take out both alternators. Combine this with inadequate warning systems makes it a recipe for trouble. I replaced the system with the Plane Power alternators. I highly recommend it for safety and reliability. However, if you don't take that advice, I can offer you spare parts for the old system at a good price.

Thanks, Pat & Kristin. Some food for thought.

Let me get my head wrapped around all of this.

Frank

Just another bit of info for the plane power conversions. If for whatever reason you pop a circuit breaker on the left or right alternator feed circuit
breaker, the warning light will not show the alternator inop. I know this as when I did my annual engine shutdowns/feather in flight, after starting the left engine back up, the 50 amp circuit breaker popped because of the current drain from all electrical load including the starter load. I only realized that the circuit breaker was popped the next day when after the engine start the alternator was not charging even though the warning light was not illuminated. Pushing in the breaker restored the charging on that engine.
That warning light is obviously not the best indicator of the charging of the system.. it only tells you that the alternator field is being powered and the alternator is producing voltage , doesn't give you a clue as to whether its providing power to the ship.

Just a heads up for the twinco drivers with Plane Power Alts.
Gary

Thanks, Gary. Crucial info!!
Steen

Wow that is good to know - thanks Gary.

- Charles