bicyclop(at)pacbell.net
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 Posted: Mon Jun 18, 2007 11:06 pm Post subject: Regulator trouble? Probable resolution |
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I've been e-mailing with Tim over at B and C (very helpful guy) and
here's what I just sent him:
Howdy Tim,
I checked it out using your troubleshooting guide. Results:
Resistance from batt neg to pin 7 0.0 - 0.1 ohms batt to
engine case 0.0 - 0.1 ohms
Buss volts 12.42 volts
Pin 3 12.33 - 12.40 v (several measurements)
Pin 6 12.07 v
Pin 4 11.02 v
Field terminal 10.86 v
B lead 12.42 v
Everything seemed pretty nominal until I was trying to get a probe into
the field connector on the alternator where I noticed the field wire
looking a little frayed. A very small tug removed it entirely. The wires
had no support for the insulation, just the crimp on the wire itself
which is where it broke.
My theory: The connection would intermittently not conduct too well
and the output voltage on the B lead would drop. The regulator would
respond by pushing the field voltage up and when the connection got
better again, the alternator output voltage would surge in response to
the high field voltage and trip the OVM. Logical?
I put some heat shrink on the wires to give them some support and
reassembled. Started but not yet flown. I expect that the problem is
solved. Time will tell. If inflight voltage stabilizes at less than
14.4, I guess I'll have to crawl under the panel and reset it. What's
the ideal voltage for charging an RG battery?
Thanks for help.
Ed Holyoke
Thanks for all the advice. If it misbehaves again, I'll let y'all know.
Robert L. Nuckolls, III wrote:
| Quote: |
<nuckollsr(at)cox.net>
At 12:18 PM 6/18/2007 -0400, you wrote:
>
>
> I have a slightly different take on this as it seems there might
> already be some clues here.
>
> Shouldn't the field voltage go above 8 volts when the alternator is
> loaded on the ground. If it is putting out less that 14.4 volts at
> low rpm - why isn't the field voltage up around 12 or 13? High
> resistance somewhere in the field?
The voltage will go that high only if one approaches the alternator's
maximum available output current for that RPM. In this case, he cites
a 17A load and ramp idle RPM.
> Next I'd want to know why 14.7 volts while taxiing in. Is the
> regulator voltage going up when it is hot? Does it not throttle back
> far enough under light load? Is there a connection that is high
> resistance when hot such that the regulator is sensing 14.4 but
> putting out 14.7 upstream where the voltmeter is located? Or is it an
> inaccurate voltmeter?
There's a ton of variables which can stack up to push the setpoint
around a bit . . . what we're interested in finding is an instability
that accounts for the nuisance trip of an OV protection system set to
operate at 16.2 volts or so.
> If the connections have already been checked, I'd be tempted to
> temporarilly wire in a cheap regulator and see what happens.
A cheap regulator wouldn't have the ov protection built in. It
WOULD be a useful experiment to temporarily wire in a substitute
regulator and a separate OV sensor. I think I've got some hardware
laying around we can send him if we don't see something really
profound . . . or he's unable to observe a field and bus voltage
surge associated with the nuisance trip.
Bob . . .
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