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lists(at)stevet.net
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 Posted: Mon Sep 24, 2012 11:42 am Post subject: Need Help Troubleshooting |
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I've got a situation that appeared rather suddenly and I'm not sure where to start. I was doing some tough-n-goes the other day when one of my low voltage lights started flashing on downwind.
I've got a dual electrical system based on Z-14 with two LR3C-14s installed. For the last 60 hours, everything has been running perfect. I fire up the engine and I get 2 readings of 14.2 volts at idle. Suddenly, one of the systems will not deliver any alternator voltage at idle. If I bring the engine back to idle at any point, whether it be on the ground or in the air, the voltage drops to 12.2 and begins a slow fall from there. As I increase the RPMs, the voltage again rises to 14.2. The second system holds 14.2 volts the entire time.
Is there a way to figure out whether my problem is with the LR3C-14 or with the alternator itself? Or possibly with my field circuit breaker? Or with the alternator switch? I haven't a clue where to even begin. Suggestions welcome.
Steve Thomas
________________________________________________________________________
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Mauledriver(at)nc.rr.com
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| Posted: Mon Sep 24, 2012 2:42 pm Post subject: Need Help Troubleshooting |
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Steve, this is just a shot in the dark. A fully charged battery with no
load should be producing over 12.6 volts. I'm wondering if you've lost
a battery.
Bill Watson
RV10 - Z-14
On 9/24/2012 3:41 PM, Steve Thomas wrote:
| Quote: |
I've got a situation that appeared rather suddenly and I'm not sure where to start. I was doing some tough-n-goes the other day when one of my low voltage lights started flashing on downwind.
I've got a dual electrical system based on Z-14 with two LR3C-14s installed. For the last 60 hours, everything has been running perfect. I fire up the engine and I get 2 readings of 14.2 volts at idle. Suddenly, one of the systems will not deliver any alternator voltage at idle. If I bring the engine back to idle at any point, whether it be on the ground or in the air, the voltage drops to 12.2 and begins a slow fall from there. As I increase the RPMs, the voltage again rises to 14.2. The second system holds 14.2 volts the entire time.
Is there a way to figure out whether my problem is with the LR3C-14 or with the alternator itself? Or possibly with my field circuit breaker? Or with the alternator switch? I haven't a clue where to even begin. Suggestions welcome.
Steve Thomas
________________________________________________________________________
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nuckolls.bob(at)aeroelect
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| Posted: Mon Sep 24, 2012 4:43 pm Post subject: Need Help Troubleshooting |
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At 02:41 PM 9/24/2012, you wrote:
--> AeroElectric-List message posted by: Steve Thomas <lists(at)stevet.net>
I've got a situation that appeared rather suddenly and I'm not sure where to start. I was doing some tough-n-goes the other day when one of my low voltage lights started flashing on downwind.
I've got a dual electrical system based on Z-14 with two LR3C-14s installed. For the last 60 hours, everything has been running perfect. I fire up the engine and I get 2 readings of 14.2 volts at idle. Suddenly, one of the systems will not deliver any alternator voltage at idle. If I bring the engine back to idle at any point, whether it be on the ground or in the air, the voltage drops to 12.2 and begins a slow fall from there. As I increase the RPMs, the voltage again rises to 14.2. The second system holds 14.2 volts the entire time.
Do you not know which of the two systems is
powered by the SD-20 and which is powered by
the main alternator?
Is there a way to figure out whether my problem is with the LR3C-14 or with the alternator itself? Or possibly with my field circuit breaker? Or with the alternator switch? I haven't a clue where to even begin. Suggestions welcome.
I'm not sure anything is wrong. The SD-20 alternator
is DE-RATED to 20A due to limitations in RPM available
at the vacuum pump pad. The alternator begins life as
a 40A ND which is disassembled for salvage of useful
components and reassembled with new front end bell,
shaft mods, sheer coupling and removal of built in
regulator.
Borrowing from the B&C website we see this data
table:
[img]cid:.0[/img]
Assuming 1:1.4 step up gearing for the vacuum
pump pad, a ramp taxi RPM of say 1000 yields
alternator RPM of 1400 where it can be
expected to deliver less than 15A. If bus
loads on the Aux alternator are significant,
bus voltage on that side can be expected to
drop below 13.0v warning value and the battery
will be expected to pick up some slack at voltages
similar to those you cited.
I would recommend that ground ops be conducted
with the cross-feed contactor closed except to
check Aux Alternator output during pre-flight
run up. After take off, add "Cross-feed Contactor-OPEN"
to your post departure checklist. You would also
reclose the cross-feed contactor during pre-landing
checklist.
The fact that you USED to get 14.2 at ground idle
before suggests that the cross-feed contactor
was closed. Now that you're seeing this disparity
of voltage between the two busses suggests that
the cross-feed contactor is open and the Aux
Alternator is performing pretty much as expected.
I wonder if -either- you've changed your modus
operandi for cross-feed management -or- the contactor
has become unavailable for some reason.
In any case, you should KNOW which of the two
alternators is used to power which suite of goodies
on the panel. This is an essential component of
plan-B development for operations with the Main
Alternator crapped.
Bob . . .
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lists(at)stevet.net
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| Posted: Tue Sep 25, 2012 9:20 am Post subject: Need Help Troubleshooting |
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I should have been more specific. What I have is a Mazda 2 rotor with two 70 amp alternators. The batteries, two each, are Panasonic LC-RD 1217P. I never start with the cross-feed closed. In fact, I don't ever recall ever using the cross-feed. The starter is connected to system 1, the system that is now failing. The last start, while running the test, was sharp and crisp. The alternators are Bosh with the internal regulators removed.
The split of devices running on each system is well known, but I don't see the relevance. The cross-feed is a backup position that, until now, has not been needed. And, since I was in the pattern when it failed, there was no need to engage - even if I had remembered. I don't know the RPMs of the alternators at idle, but, it was working fine.
Steve Thomas
________________________________________________________________________
On Sep 24, 2012, at 5:42 PM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
[quote] At 02:41 PM 9/24/2012, you wrote:
--> AeroElectric-List message posted by: Steve Thomas <lists(at)stevet.net (lists(at)stevet.net)>
I've got a situation that appeared rather suddenly and I'm not sure where to start. I was doing some tough-n-goes the other day when one of my low voltage lights started flashing on downwind.
I've got a dual electrical system based on Z-14 with two LR3C-14s installed. For the last 60 hours, everything has been running perfect. I fire up the engine and I get 2 readings of 14.2 volts at idle. Suddenly, one of the systems will not deliver any alternator voltage at idle. If I bring the engine back to idle at any point, whether it be on the ground or in the air, the voltage drops to 12.2 and begins a slow fall from there. As I increase the RPMs, the voltage again rises to 14.2. The second system holds 14.2 volts the entire time.
Do you not know which of the two systems is
powered by the SD-20 and which is powered by
the main alternator?
Is there a way to figure out whether my problem is with the LR3C-14 or with the alternator itself? Or possibly with my field circuit breaker? Or with the alternator switch? I haven't a clue where to even begin. Suggestions welcome.
I'm not sure anything is wrong. The SD-20 alternator
is DE-RATED to 20A due to limitations in RPM available
at the vacuum pump pad. The alternator begins life as
a 40A ND which is disassembled for salvage of useful
components and reassembled with new front end bell,
shaft mods, sheer coupling and removal of built in
regulator.
Borrowing from the B&C website we see this data
table:
<dd29ce3.jpg>
Assuming 1:1.4 step up gearing for the vacuum
pump pad, a ramp taxi RPM of say 1000 yields
alternator RPM of 1400 where it can be
expected to deliver less than 15A. If bus
loads on the Aux alternator are significant,
bus voltage on that side can be expected to
drop below 13.0v warning value and the battery
will be expected to pick up some slack at voltages
similar to those you cited.
I would recommend that ground ops be conducted
with the cross-feed contactor closed except to
check Aux Alternator output during pre-flight
run up. After take off, add "Cross-feed Contactor-OPEN"
to your post departure checklist. You would also
reclose the cross-feed contactor during pre-landing
checklist.
The fact that you USED to get 14.2 at ground idle
before suggests that the cross-feed contactor
was closed. Now that you're seeing this disparity
of voltage between the two busses suggests that
the cross-feed contactor is open and the Aux
Alternator is performing pretty much as expected.
I wonder if -either- you've changed your modus
operandi for cross-feed management -or- the contactor
has become unavailable for some reason.
In any case, you should KNOW which of the two
alternators is used to power which suite of goodies
on the panel. This is an essential component of
plan-B development for operations with the Main
Alternator crapped.
Bob . . .
[b]
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Tue Sep 25, 2012 11:53 am Post subject: Need Help Troubleshooting |
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At 12:18 PM 9/25/2012, you wrote:
| Quote: | I should have been more specific. What I have is a Mazda 2 rotor
with two 70 amp alternators. The batteries, two each, are Panasonic
LC-RD 1217P. I never start with the cross-feed closed. In fact, I
don't ever recall ever using the cross-feed. The starter is
connected to system 1, the system that is now failing. The last
start, while running the test, was sharp and crisp. The alternators
are Bosh with the internal regulators removed.
The split of devices running on each system is well known, but I
don't see the relevance. The cross-feed is a backup position that,
until now, has not been needed. And, since I was in the pattern
when it failed, there was no need to engage - even if I had
remembered. I don't know the RPMs of the alternators at idle, but,
it was working fine.
|
Sorry. The vast majority of two-alternator systems
we work with are on aircraft engines where one
alternator is driven from the now vacant vacuum
pump pad.
Okay, we're troubleshooting a single alternator/
battery combination. Have you run the traps on
the LR3 regulator per B&C documents?
http://tinyurl.com/bowymay
Knowing how the FIELD output voltage from the
LR-3 is behaving when you're experiencing
a problem is critical to deciding whether
the difficulty lies with the alternator or
regulator.
Bob . . .
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lists(at)stevet.net
Guest
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| Posted: Tue Sep 25, 2012 1:37 pm Post subject: Need Help Troubleshooting |
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Not yet. Will do ASAP and reply.
Steve Thomas
________________________________________________________________________
On Sep 25, 2012, at 12:50 PM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com> wrote:
| Quote: | Have you run the traps on
the LR3 regulator per B&C documents?
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lists(at)stevet.net
Guest
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| Posted: Thu Sep 27, 2012 2:50 pm Post subject: Need Help Troubleshooting |
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I ran the tests and it looks like I have a bad regulator. Test #4, where you check the voltage of pin #4, failed. It was showing only 2.8 volts. I'll contact B & C and figure out where to go. Thanks for the help, Bob.
Steve Thomas
________________________________________________________________________
On Sep 25, 2012, at 2:34 PM, Steve Thomas <lists(at)stevet.net> wrote:
| Quote: |
Not yet. Will do ASAP and reply.
Steve Thomas
________________________________________________________________________
On Sep 25, 2012, at 12:50 PM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com> wrote:
> Have you run the traps on
> the LR3 regulator per B&C documents?
|
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