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sblack
Joined: 14 Aug 2010
Posts: 21
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 Posted: Sun Aug 22, 2010 7:23 pm Post subject: B&C alt voltage goes right up to 16V |
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I installed a b&c alt on an o200 with the PMR1C-14. After about 10 hrs on it with no problems one morning, after the airplane sat out in the rain, the voltage started going right up to 16V at takeoff power tripping the crowbar OV protection. The reg. is mounted on the firewall with the wires exiting downwards. I do see how water could have gotten into it. I have not played with the setpoint since it was working fine at the beginning (stayed just under 14v) so it should not have changed. My battery acts fine, takes a charge in a reasonable amount of time and my volt meter is correct as I checked it with another and the crowbar goes off and just the right voltage. What could cause this? For what it's worth I draw about 3amps from my panel as I have no lights and not much in the way of avionics. Any advice appreciated.
Scott
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Scott Black
Montreal
Jodel F11 O-200 |
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user9253
Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan
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| Posted: Mon Aug 23, 2010 5:39 am Post subject: Re: B&C alt voltage goes right up to 16V |
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You confirmed that there is indeed an over-voltage condition. The voltage regulator is not doing its job, for whatever reason. The rain may or may not be a factor. Perhaps the regulator got too hot at some point. If you can not adjust the output voltage to within normal range, then the voltage regulator should be replaced.
Joe
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Joe Gores |
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user9253
Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan
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| Posted: Mon Aug 23, 2010 6:19 am Post subject: Re: B&C alt voltage goes right up to 16V |
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There is another possibility, depending on where in the circuit the voltage regulator measures the voltage. If there is a high resistance in the field circuit, the regulator might be seeing a lower voltage than is at the main bus. In that case, the regulator would tell the alternator to put out more. Make sure that all of the connections in the electrical system are secure, especially in the regulator sense and field circuits.
Joe
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Joe Gores |
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sblack
Joined: 14 Aug 2010
Posts: 21
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| Posted: Mon Aug 23, 2010 9:00 am Post subject: Re: B&C alt voltage goes right up to 16V |
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I apologize Joe, I did not provide enough detail. There is an overvoltage condition and the OV circuit does its job and takes the alternator off line at 16V. I have verified that the indicated voltage is correct. Also, it is a permanent magnet alternator (B&C G200) so there is no field winding.
Basically when I start up, at idle the voltage sits around 12V and when I do my runup it just starts climbing, gradually. I have to let it run at 1500 rpm for say a minute, or start the takeoff run (in which case it climbs faster) and then POP, off goes the OV.
thanks
Scott
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Scott Black
Montreal
Jodel F11 O-200 |
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user9253
Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan
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| Posted: Mon Aug 23, 2010 5:19 pm Post subject: Re: B&C alt voltage goes right up to 16V |
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| Quote: | | I have not played with the setpoint since it was working fine at the beginning |
Scott,
I got the impression from your first posting that the regulator has a set point adjustment. If the connections are all good and you are sure that there is no rain water in the regulator or connectors, then I would try adjusting the regulator. If that does not work, then replace the regulator. If the regulator "sense" terminal is seeing the actual bus voltage but still allows the alternator to put out more than 14.5 volts, then the regulator is not doing its job. Regulators installed in a high ambient temperature location will have a shorter life expectancy.
It is a good thing that there is over-voltage protection. Some electronics can be damaged by high voltage.
Joe
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