The Auto Electric industry in transition
osxuser said:
George, what you describe as the dummy lead is a volt sense lead on some ND clone Alternators. On the one I installed in a Glasair (NOT from Vans, from NAPA) it HAD to be hook up to bus or else output went up to ~18VDC. Crappy regulator in that one I guess.
18 volts is a little high but it happens.
Yep probably a regulator.
Now I take it that you did not have the warning light hooked up? I suspect the light would have went on (if you had it hooked up) before 18 volts. The specs say the light is set at 16.5 volts, but it varies by model of ND. However NAPA may sell a clone copy ND that may not meet all OEM specs. In fact its very possible it does not met specs or quality. It is hit and miss and the most frustrating thing with auto electric supply industry today. Really its always been kind of hit or miss industry.
Not all "clone" alternators are made with nippondenso parts or parts that meet OEM specs. In my research and following the topic, I find OV conditions are rare, and when it does happen it's mild, 16-18 volts range. One way to control it of course is lower RPM a little and/or add electrical load, landing lights and nav or strobes. However 18 volts does not totally surprise me, but it is on the high side. Most all new avionics can handle up to 30 volts with out skipping a beat.
Why do cars with ND alternators have few failures and over voltages compared to RV (glasair) builders?
There two reasons that this happens: The Pilot and Quality
Yes, you had an OV, probably caused by a bad regulator, but it is rare. Millions of cars/trucks/tractors all over the world are going 24/7 with out problems. Some times it is a bad regulator, but some times its a good regulator damaged by the pilot.
My pet peeve as you might know is PIF - Pilot Induced Failures.
Turning the alternator on and off while the engine is running under electrical load is a no no. In a car when you operate one of these IR (internal regulated) alternators (which they where designed for) you turn it on (wake it up) before starting the engine and leave on until you shut the engine down; that is the way it was designed to work. However in a car the alternator operations are all controlled with the sequence ignition switch, so the driver is out of the loop. In a plane however, the pilots has that little ALT switch, which they can't resist touching to see what happens.
I know what happens, it can fry the regulator. The "IGN" lead is just there to tell the alternator to get ready to go to work, wake-up, or it tells the alternator to sleep, go to standby so it does not drain the battery. When you play with it while the engine is under load it can damage the regulator. Many a fried regulator I have studied had one thing in common, a pilot that like to throw switches. I have no absolute proof but there is a common thread.
The other problem with Vans, may be NAPA and certainty the whole aftermarket Auto-electrical business is inconsistent quality and specs. Like the used car salesman, "rebuilt" alternators and starters have always had a poor reputation in the auto maintenance business, for decades. The industry is now in transition from rebuilding to inexpensive new "clones" from China. It's just cheaper to buy a new aftermarket unit than rebuild an old one an make money at it. Not all China clones are good, some are.
Now we have Plane Power and Van is getting with better quality clones, so I think the situation is better.
I have no problem with going to NAPA, AutoZone or Pep Boys. They offer life time warranties and they are convenient. If it dies, take it out and go get a new one. You really don't have a lot of choice. ND doesn't make new OEM units in the out of production size/model that's popular with the homebuilt plane crowd (aka the 55/60 amp Suzuki or +60 amp corolla), so your choice is rebuilt, clone or specialty (Plane power, B&C).
However if going IFR, I would go with the "plane power" brand. I went with an OEM genuine ND from a folk lift. Its expensive, but I know the quality is there. If doing it today, I'd get a Plane Power (IR) unit. Regardless of how you go nothing is perfect. However there are some sub par units being sold, just be aware. Whether NAPA was selling low quality, I don't know. I know you would never turn your alternator on/off with the engine running.