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s_kilishek(at)yahoo.com
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 Posted: Wed Jan 03, 2007 2:55 pm Post subject: What Are The Odds - Problem Solved (I think) |
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Bob:
As usual, your intuition (in this case about faulty
ground connections) is right on target.
I replaced the alternator ground wire, which had run
to a nearby engine bolt, with a piece of #18 wire
going directly to the regulator case.
All aberrant behavior stopped at once. Bus voltage is
now mostly 14.6 to 14.8 volts, with infrequent
excursions to 14.4 or 15.0 volts.
Don’t know why this worked, since the original ground
connection tested fine on the multimeter (showed zero
ohms to airframe ground), but who am I to question
success?
I’ll put some additional flight test time on the
system when the weather improves, but I’m feeling
pretty confident that the problem is solved. I know
that a 14.8V bus voltage will put more stress on the
battery than 13.8 volts would, but I think we can
probably live with that. I don’t think that this will
hurt the avionics.
In answer to your questions:
My ground system is as follows. The voltage regulator
is bolted to the stainless steel firewall. The
landing light and strobes are grounded to the wing
structure. The PTT switches are grounded to
convenient points near the control sticks. Everything
else is grounded at a single accessible point behind
the instrument panel.
With the exception of the 60A alternator B lead
breaker (which is a push to reset thermal breaker) all
circuit breakers are Polyswitch PTC current limiters
with indicator lights for each circuit.
I know that I speak for many others when I express my
sincere gratitude to you for monitoring this list and
for steering dummies like me away from despair. God
bless you.
George Kilishek
---------------------------------------
/snip/
| Quote: | The fact that the voltage the regulator sees is a few
>tenths of a volt lower than the actual bus
|
voltage
>probably indicates a problem with the wiring
between
>the regulator and the alternator breaker. This
is
>about 6 feet of #18 wire from the regulator to
the
>alternator switch and about 2 feet of #18 wire
from
>the switch to the breaker (Faston connectors
>throughout).
>
>Do you have any suggestions?
Keep in mind that "wiring" includes ALL
conductor
pathways including ground. These simple
regulators
use case ground as the negative side sense
lead
for voltage regulation. /snip/
__________________________________________________
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bakerocb
Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA
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| Posted: Thu Jan 04, 2007 8:27 pm Post subject: What Are The Odds - Problem Solved (I think) |
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01/04/2007
Hello George, You wrote: "The voltage regulator is bolted to the stainless
steel firewall."
A stainless steel firewall can make a very poor grounding connection because
of a film that forms on the surface of the stainless steel.
Sharp points of a meter's probes can pierce this film, but the flat bolted
on base of a voltage regulator may not make a good electrical connection.
There is more in the archives on this subject.
OC -- The best investment we will ever make is in gathering knowledge.
Time: 02:55:28 PM PST US
From: Sally Kilishek <s_kilishek(at)yahoo.com>
Subject: Re: What Are The Odds - Problem Solved (I think)
Bob:
As usual, your intuition (in this case about faulty
ground connections) is right on target.
I replaced the alternator ground wire, which had run
to a nearby engine bolt, with a piece of #18 wire
going directly to the regulator case.
All aberrant behavior stopped at once. Bus voltage is
now mostly 14.6 to 14.8 volts, with infrequent
excursions to 14.4 or 15.0 volts.
Dont know why this worked, since the original ground
connection tested fine on the multimeter (showed zero
ohms to airframe ground), but who am I to question
success?
Ill put some additional flight test time on the
system when the weather improves, but Im feeling
pretty confident that the problem is solved. I know
that a 14.8V bus voltage will put more stress on the
battery than 13.8 volts would, but I think we can
probably live with that. I dont think that this will
hurt the avionics.
In answer to your questions:
My ground system is as follows. The voltage regulator
is bolted to the stainless steel firewall. The
landing light and strobes are grounded to the wing
structure. The PTT switches are grounded to
convenient points near the control sticks. Everything
else is grounded at a single accessible point behind
the instrument panel.
With the exception of the 60A alternator B lead
breaker (which is a push to reset thermal breaker) all
circuit breakers are Polyswitch PTC current limiters
with indicator lights for each circuit.
I know that I speak for many others when I express my
sincere gratitude to you for monitoring this list and
for steering dummies like me away from despair. God
bless you.
George Kilishek
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
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