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  #21  
Old 11-18-2013, 06:27 AM
Mich48041 Mich48041 is offline
 
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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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  #22  
Old 11-18-2013, 07:07 AM
Valentine Valentine is offline
 
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Default Coolant?

Make & model of engine please.
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  #23  
Old 11-18-2013, 07:31 AM
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Quote:
Originally Posted by Valentine View Post
Make & model of engine please.
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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  #24  
Old 11-18-2013, 07:51 AM
ChuckC ChuckC is offline
 
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Building ELSA. So, using the Rotax 912.
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  #25  
Old 11-18-2013, 08:14 AM
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flion flion is offline
 
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Quote:
Originally Posted by ChuckC View Post
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.
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.
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  #26  
Old 11-18-2013, 08:23 AM
AWakem8 AWakem8 is offline
 
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Location: Belfast Maine
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Default 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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  #27  
Old 11-18-2013, 08:27 AM
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txaviator txaviator is offline
 
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Default 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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  #28  
Old 11-18-2013, 08:35 AM
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ColoRv ColoRv is offline
 
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Just another WAG here, but is the engine grounded?
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  #29  
Old 11-18-2013, 08:44 AM
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Mike S Mike S is offline
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Quote:
Originally Posted by E. D. Eliot View Post
Are you sure that your battery is fully charged? Could be as simple as using a fully charged battery.
This.

Quote:
Originally Posted by ChuckC View Post
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.
Starter solenoid.

They chatter due to either low battery voltage, or bad connections not letting full battery voltage through.

Quote:
Originally Posted by ColoRv View Post
but is the engine grounded?
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.
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  #30  
Old 11-18-2013, 12:28 PM
Warden Warden is offline
 
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Location: Mid Michigan
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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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