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echristley(at)nc.rr.com
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 Posted: Tue May 30, 2006 6:48 am Post subject: alternator trouble shooting |
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On May 29, 2006, at 9:56 AM, Greg Grigson wrote:
| Quote: | >
> <iflyhawaii2(at)yahoo.com>
>
> Wow. I replaced the first Van's alternator at 10 hours due to amps
> jumping from + 32 amps to - 32 amps. I would hate to just replace
> the second alternator. Is there a way to test it on the plane?
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Yes. Put it under some kind of load and look at the output with an
oscilloscope. Just connect the o-scope to the main distribution bus
where the alternator B-lead connects. Do you have a 12VDC power jack
for your GPS? That will work too and it is very easy to get to.
An alternator with all three phases working will have almost ripple-
free output. An alternator that has lost a diode will lose the phase
associated with that diode. The result will be greatly increased
ripple in the bus voltage. (That ripple is what you are hearing in
your comm radio.) Some automotive test meters have an "alternator
test" scale that just measures the amount of ripple and gives you a
"good/bad" reading which accomplishes essentially the same thing.
Brian Lloyd 361 Catterline Way
brian-yak AT lloyd DOT com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
Antoine de Saint-Exupry
Another tactic is to use a digital volt meter, one of those $3 Harbor Freight jobs, and read the bus voltage on the AC scale. AC volts will be zero on the battery, starts increasing when the alternator is brought online and slowly gets progressively worse as the loading increase. It takes a big jump when a diode goes out.
--
,|"|"|, Ernest Christley |
----===<{{(oQo)}}>===---- Dyke Delta Builder |
o| d |o www.ernest.isa-geek.org |
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iflyhawaii2(at)yahoo.com
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| Posted: Tue May 30, 2006 10:25 pm Post subject: alternator trouble shooting |
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OK Good advice. I'll test the alternator and get back to you.
Thanks.
Greg
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