Voltage Regulator Fun

[jjhoneck]

Since Day One with our new (to us) RV-8A, we have had a hinky charging system. It would not pop the alternator breaker, but rather would simply drop offline entirely. The amp meter would drop to zero, and voltage would drop, too.

After this happened during the ferry flight from Vermont, we had installed a new alternator, after the old one tested bad, but to no avail. Despite this, it would still come, and go -- and then, just as suddenly, it would cure itself and be normal for a few flights. Very frustrating!

I ordered a replacement voltage regulator, and kept it handy, ready for the day when it would finally fail completely.

So last night (actually, four flights ago) the regulator finally failed 99%. We landed last night with low voltage alarms going off, and a mostly dead battery.

I put the new one in (three bolts, three wires), and today we tested the plane with it installed, and a fully charged battery. Amperage was perfect, but the thing was now letting the alternator work TOO good. It was putting out 15.3 volts.

So I called my buddy, Tom Berge, for advice. He said that there's a screw on the back of the unit you can turn to adjust the voltage output. Cool.

So, I take the whole thing out -- and there is no adjustment screw. The part they sent me was #305. I needed #305-A.

Guess what "A" stands for? Uh huh. Adjustable.

So, I call Concorde, the battery company and speak with some 106-year-old dude that still works in their aircraft battery department. He affirms that 15.3 volts will destroy the battery. 14.2 volts is optimal.

So, I'm about to drive off the island to Corpus Christi, to search for an adjustable voltage regulator, when I take one last look at part #305. I hold it up next to #305-A, and note that they are 100% identical, except that the new part has a poured-in rubber material on the back, and no adjustment screw.

I then tilt it a bit into the light, and note a very slight indentation -- precisely where the screw is on the 305-A.

You don't suppose...?

What have I got to lose? I take a razor blade and carefully cut around the perimeter of the indented rubber, and peel it back.

Revealing...an adjustment screw! So, I give it a quarter turn, reinstall -- and voltage drops to 14.9. Pull it out, give it another quarter turn, and voltage drop a to a perfect 14.2 volts.

We put everything back together and just finished a 0.7 hour test flight, to get it good and hot, under various loads.

Voltage remained rock steady, while the amp meter actually acted normally, for the first time since we bought this plane. It showed higher output under load and at start-up, with lower, stable readings in cruise flight.

All is finally right with Amelia's electrical system. Yippee!

We will be loading her up tonight, for a Saturday morning departure, heading for Oshkosh! Happy happy!

[Neal@F14]

For an external voltage regulator.... a BWD "Select" part# R400 (for a mid-late 1970's Ford LTD with 351/400/460 V8 engines... $27 at AutoZone, O'Reilly's, NAPA, etc) works beautiful in an RV with the original Van's supplied Honda-style alternator that uses an external regulator. That's what's in my RV-6 now.... and gives a nice steady 14.2v

[Bob Kuykendall]

Originally Posted by jjhoneck

...So, I'm about to drive off the island to Corpus Christi, to search for an adjustable voltage regulator, when I take one last look at part #305. I hold it up next to #305-A, and note that they are 100% identical, except that the new part has a poured-in rubber material on the back, and no adjustment screw.

I then tilt it a bit into the light, and note a very slight indentation -- precisely where the screw is on the 305-A.

You don't suppose...?

What have I got to lose? I take a razor blade and carefully cut around the perimeter of the indented rubber, and peel it back.

Revealing...an adjustment screw! So, I give it a quarter turn, reinstall -- and voltage drops to 14.9. Pull it out, give it another quarter turn, and voltage drop a to a perfect 14.2 volts...

One of the themes of Make Magazine is that if you can't open it, you don't really own it. Well, you now own that voltage regulator. Good work!

[jjhoneck]

Originally Posted by Bob Kuykendall

One of the themes of Make Magazine is that if you can't open it, you don't really own it. Well, you now own that voltage regulator. Good work!

Thanks! Inspiration, inspired by desperation, is the very best kind of innovation.

Or something like that...