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Bill Reining
Joined: 13 Aug 2007
Posts: 13
Location: Oakland, California
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 Posted: Fri Nov 14, 2014 10:21 pm Post subject: Charging system problem - please help troubleshoot |
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Cessna 182J with 60A alternator, mechanical regulator, no overvoltage circuit. Alternator quit charging - shop found brushes totally worn, slip rings out of round, and rear bearing noisy. Slip rings trued, brushes replaced, bearing replaced. Bench and flight tested OK. But on subsequent trip from Calif. to OSH, following problem occured: about an hour into each leg static would appear in VHF and ammeter would flicker rapidly between charge and discharge. Turned off the alternator field with the split master switch, waited a few minutes, then turned it back on. System resumed charging normally. Replaced the regulator at OSH with a solid state unit by Zeftronics. On way back to Calif. had similar problem, only this time the system would simply stop charging, as evidenced by an alert on the JPI engine analyzer that the system voltage had fallen into the 12 volt range. As before, I could turn off the field, wait a few minutes and then restore normal operation (13.9 volts) by turning the field back on. It would seem something is overheating. Diodes in alternator? Bad field switch contact? Bad breaker? Bad capacitor?
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user9253
Joined: 28 Mar 2008
Posts: 1922
Location: Riley TWP Michigan
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| Posted: Sat Nov 15, 2014 6:19 am Post subject: Re: Charging system problem - please help troubleshoot |
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The vast majority of electrical problems are due to bad connections, either terminals or switch contacts. Check the alternator half of the master switch. For troubleshooting with the engine off, connect a high wattage lamp to the regulator ground and to the BATTERY terminal of the regulator. The lamp should light up. Measure the voltage across the lamp. It should be close to battery voltage. If the lamp does not light up or the voltage across the lamp is low, then use the voltmeter to find where the voltage is being dropped.
Joe
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Joe Gores |
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skywagon
Joined: 11 Feb 2006
Posts: 184
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| Posted: Sat Nov 15, 2014 8:43 am Post subject: Charging system problem - please help troubleshoot |
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I had a similar alternator problem, however, it was in an RV. . .
It would operate fine for a while and then get intermittent or simply quit
charging.
On cold restart it worked fine. . .
When thru many tests and no one could not find the problem.
Finally went to another electrical shop an found an older gray haired
technician. He too ran the same test as others and could not find the
failure.
His finally test was to take the alternator apart and visually inspection
the rather large gauge wiring of the "stator". He used a magnifying glass
and what he found was, where the end of the stator wire was swaged into the
case boss, it was cracked. It was a hairline crack that was mostly
invisible to the naked eye. It was a manufacturing error during the
swaggering step but got thru the system and into an RV chassis.
When the alternator got hot from charging and latent engine heat that
cracked stator wire would randomly open or stay open while hot.
Fix was a new alternator. . . .
Dave
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skywagon
Joined: 11 Feb 2006
Posts: 184
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| Posted: Sat Nov 15, 2014 12:27 pm Post subject: Charging system problem - please help troubleshoot |
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The older legacy Cessna's and maybe others used a single push-pull Master
switch instead of the more common split masters. The switch contained two
contact circuits on one switch. One controlled the field of the charging
system.
This switch is normally very robust.
However, when problems of non-functioning or intermittent problems with the
charging system there is an odd problem with this switch that should always
be checked.
The exterior terminals are riveted thru to the interior contacts. The
rivets and screw terminal use different metals. I have found some of these
terminals loose under the rivet. They can be rotated slightly when there is
a problem.
I do not know if the looseness comes from. . .aging, wiring abuse when
electrical service work is done under the panel, or electrolysis from the
different metals and moisture.
If you are having charging problems and use this type of master swt., be
sure to check the "tightness" of this riveted joint. Any looseness is a
problem. D
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