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11-18-2013, 06:27 AM
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Join Date: Apr 2008
Location: Riley TWP MI
Posts: 3,070
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13 volts is fully charged, not 12.5 volts. I agree with the others that the solenoid (aka contactor) is chattering. The cause could be a bad electrical connection or a weak battery or a bad starter motor. This is what causes the chattering: the voltage is high enough to energize the contactor, but the heavy load of the starter causes the voltage to drop so much that the contactor opens up and you hear a click. Now that the contactor is open and no heavy current is flowing, the voltage goes back up and the contactor energizes again and you hear another click. This sequence is repeated over and over several times per second and you hear the buzzing or chattering.
Joe Gores
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11-18-2013, 07:07 AM
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Join Date: May 2011
Location: Paso Robles, CA
Posts: 25
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Coolant?
Make & model of engine please.
__________________
Hal
Finally sold N7HK
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11-18-2013, 07:31 AM
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Join Date: Jul 2011
Location: Ellsworth, ME
Posts: 842
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Quote:
Originally Posted by Valentine
Make & model of engine please.
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99.9% chance it is a Rotax 912 if he is building the RV12 as an E-LSA as most guys do.
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11-18-2013, 07:51 AM
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Join Date: Apr 2011
Location: Meridian, ID
Posts: 71
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Building ELSA. So, using the Rotax 912.
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Chuck Carlson
120445
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11-18-2013, 08:14 AM
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Join Date: Dec 2007
Location: Flagstaff, AZ
Posts: 2,653
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Quote:
Originally Posted by ChuckC
Yes, the battery is fully charged showing 12.5 on charger and Skyview. Did check all the wiring connections - visually and tugging, and, they all appeared solid.
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With most advice pointing to the battery or connections, you should test before you replace. Looking at the connections and tugging on them is not the same thing (though it is true that tugging can sometimes complete a poor connection, temporarily). Get out the multimeter. Test resistance through the connections and voltage at each point.
I don't know the -12 electrical system, but in most aircraft I would check that the ground is good at all points, that there aren't any connections with a high resistance, that resistance through the solenoid is high until engaged, and that the activation lead is seeing system voltage (to see voltage at any point, put a probe on the connection and the other probe to ground). I've seen bad solenoids but I've also seen bad grounds or switches fail to provide enough power to activate the solenoid, which results in the intermittent "machine gun" chatter that you describe. Likewise, not enough power to the starter can also cause an intermittent sound but I don't think it would sound like it was on the firewall. You'd also probably see the prop move slightly each time you activated the starter.
__________________
Patrick Kelley - Flagstaff, AZ
RV-6A N156PK - Flying too much to paint
RV-10 14MX(reserved) - Fuselage on gear
http://www.mykitlog.com/flion/
EAA Technical Counselor #5357
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11-18-2013, 08:23 AM
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Join Date: Sep 2013
Location: Belfast Maine
Posts: 8
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Brrrrrrrrr=Solenoid
Your battery is not fully charged or you have a poor connection. The "Brrrrrrrrr" sound is the starter solenoid contacting and releasing rapidly. I would suggest charging the battery first and then try again. Remember the KISS principal. I live by this and most of the time it keeps me out of trouble. 
__________________
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Andy Wakem
Belfast, Maine
Study phase RV-8 Preview Plans
2014 donation made
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11-18-2013, 08:27 AM
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Join Date: Jan 2005
Location: Arlington, TX (DFW)
Posts: 1,164
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I'm no expert, but:
I am voting that the battery (despite showing 12-volts) still doesn't have enough charge. As a result, the solenoid is chattering.
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Gary Robertson
Arlington, TX
RV-12 Built / Sold / Flying
Currently Flying: Cessna Skyhawk 172
Rebuilding a true barn find J-3 Cub
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11-18-2013, 08:35 AM
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Join Date: Apr 2012
Location: Tampa (BKV)
Posts: 926
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Just another WAG here, but is the engine grounded?
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RV-8 Flying
1,235th flying RV8
SARL Race#95
SnF Homebuilt Judge
2015 Sun n Fun Kit Built Reserve Grand Champion
2015 Oshkosh Kit Built Champion
2015 Jeffco Kit Built Grand Champion
2014 Oshkosh Outstanding Workmanship Award
Broken Warrior of the Jarhead Clan
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11-18-2013, 08:44 AM
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Senior Curmudgeon
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 15,420
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Quote:
Originally Posted by E. D. Eliot
Are you sure that your battery is fully charged? Could be as simple as using a fully charged battery.
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This.
Quote:
Originally Posted by ChuckC
To me, sitting in the cockpit, it sounds like something is battering the firewall really rapidly - fifty times faster than you could do with a hammer.
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Starter solenoid.
They chatter due to either low battery voltage, or bad connections not letting full battery voltage through.
Quote:
Originally Posted by ColoRv
but is the engine grounded?
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And this. Bad grounds are the overall biggest cause of electrical gremlins I have ever seen in half a century of wrenching of cars, boats, and planes.
__________________
Mike Starkey
VAF 909
Rv-10, N210LM.
Flying as of 12/4/2010
Phase 1 done, 2/4/2011 
Sold after 240+ wonderful hours of flight.
"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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11-18-2013, 12:28 PM
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Join Date: Nov 2013
Location: Mid Michigan
Posts: 17
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Starter drive. Check negative battery connections. Use internal/external star washers between battery terminal and cable (yes, between terminal & cable!) to achieve good electrical contact. Also, starwasher between battery negative cable and grounding point on engine.
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