Wendell Voto wrote:

I got the resistors from Mouser. They are on the internet.

Mouser.com

Part # 284-HS25-.33    (.33ohm 25 Watt)
       # 284-HS25-5        (5 ohm 25 Watt)
Wendell

That brings up a good point.
Tracy what can we do to eliminate this waste of alternator power?
Also at issue; how can we extend the range of the aircraft
on battery power alone after the alternator fails?

Paul Lamar

What waste of power? The resistors do not dissipate much - the originals are
just 5 Watts resistors, and I do not think they even dissipate that much. I
think the reasons there have been failures in aircraft is from high engine
compartment heat. The resistors are wire wound and I think the high peak
pulse current fatigues the wire. The 25 watt resistors use a larger diameter
wire, not as prone to failure. My original units are still working fine
after 175 hours with cool air blast. I once flew my Mazda Rv6 with EFI for
over one hour with the alternator turned off (within gliding distance of the
airport) and the voltage still did not drop below 12 volts. This was with a
standard 33 amp hour battery.

Chuck Dunlap

OK Chuck. So you don't think the higher average current is causing the
failure? First I have heard that high peak pulse current can fatigue wire
at about 80-100 pulses per second. Light bulbs last about 1000 to 1500 hours at
120pulses per second and the wire is incandescently hot. Of course that
is a sin wave and ignition module works off a pulse. Do you think this a thermal 
fatigue phenomena? Very interesting. Got any references on this subject
of wire wound resistor failure modes?

BTW what is the total current draw from Tracy's EFI/IGN and fuel pumps 
at 12 volts?

Paul Lamar
 
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