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  #11  
Old 01-06-2019, 09:58 PM
springer springer is offline
 
Join Date: May 2012
Location: AZ/MN
Posts: 313
Default

Had the same issue. Like gasman indicated, it was my failing master battery switch.
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  #12  
Old 01-07-2019, 12:16 AM
Ralph Ketter Ralph Ketter is offline
 
Join Date: May 2005
Location: La Luz, NM
Posts: 29
Default Don't forget the ground side

Don't forget to check the ground side also. Any poor connection or contact in the start circuit will cause cranking problems. Check that the engine ground is secure. A voltmeter can help track down bad connections. Good connections will not have a voltage drop while cranking (indicated by a significant voltage reading).

For example to check the ground side, connect the negative lead of the voltmeter to the negative battery terminal and the positive lead to the starter case while attempting to crank the engine. THIS MUST be done in a manner that will be SAFE for engine start because the next step is to observe the voltage while cranking the engine. A significant voltage indication (perhaps 0.5 volt or more) indicates a bad connection somewhere in the ground circuit. If possible leave the master switch off but still assume it is ON.

The positive or feed side can also be checked by connecting the positive voltmeter lead on the positive battery terminal and the negative lead on the starter contactor. There may be a higher voltage indication because of contactors but I think it should still be less than a volt.

If a significant voltmeter indication is found in either leg then it can be tracked down by measuring across smaller portions of the circuit.

Hope this helps but please do it safely.
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  #13  
Old 01-07-2019, 05:48 AM
Windrunner Windrunner is offline
 
Join Date: Dec 2008
Location: Keithville, Louisiana
Posts: 32
Default

My RV-9 presented with the same symptoms over a period of several months. After replacing solenoids, starter, and battery, I found intermittant master switch internal failure and the engine to firewall ground wire terminal improperly swaged; when I removed the shrink wrap to check swaging the terminal slipped off.
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  #14  
Old 01-07-2019, 07:23 AM
BigJohn BigJohn is offline
 
Join Date: Nov 2008
Location: Gloversville, NY
Posts: 1,565
Default

Sumo,

There seems to be quite a bit of confusion in this thread about the configuration of the high amperage side of your electrical system (battery, solenoids, starter, master switch and associated wiring.)

In my experience it is futile to guess at what is going wrong unless you understand the design of the system. My suggestion is that you take the time to trace out the wiring and draw a simple schematic that you can then use to help you isolate the cause of the problems. This should not be a really big task, since you only need to know how the system works at the "front end". If you don't have the skills to do this yourself I suggest you find someone to help you that is knowledgeable about electrical components and wiring.

Working on experimentals that someone else built can be frustrating, especially if the documentation is thin or non-existent. Ask me how I know!

Figure out the electrical system in your airplane, and then take a step by step approach to diagnosing the problem. Good luck!

John
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  #15  
Old 01-07-2019, 09:39 AM
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JonJay JonJay is offline
 
Join Date: Jan 2007
Location: Battleground
Posts: 4,045
Default

Quote:
Originally Posted by BigJohn View Post

Working on experimentals that someone else built can be frustrating, especially if the documentation is thin or non-existent. Ask me how I know!

Figure out the electrical system in your airplane, and then take a step by step approach to diagnosing the problem. Good luck!

John
Rarely does anyone here talk about this in terms of a prebuy for new owners. Documentation of the various systems, especially electrical, should be high on the list. This is even more important for those less skilled in aircraft systems.

As John and others suggest, take the time now to get your electrical system drawn out. even if you don't know what's what, others can more easily help with troubleshooting.
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  #16  
Old 01-07-2019, 10:07 AM
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bhester bhester is offline
 
Join Date: Jan 2005
Location: Hopkinsville, KY
Posts: 839
Red face Not parallel

Quote:
Originally Posted by Sam Buchanan View Post
Really doubt your contactors are wired in parallel......
Yep your right, I missed that part of his message.
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  #17  
Old 01-07-2019, 07:17 PM
Sumo Sumo is offline
 
Join Date: Apr 2014
Location: Las Vegas, NV
Posts: 22
Default

It's going on 15 years old now...

Quote:
Originally Posted by bhester View Post
Mine has two the first one is part of the Over voltage protection per Bob Nuckolls - AeroElectric plan. Along with my original Van's internal regulated 60A alternator 12 yrs. old (with no cooling tube) and still going, finger crossed.

How old are your? I replaced my Battery contactor my starter contactor and my battery at 8 yrs. old, just because I thought it might be a good thing to do. I haven't replaced the OV contactor.
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  #18  
Old 01-07-2019, 07:26 PM
Sumo Sumo is offline
 
Join Date: Apr 2014
Location: Las Vegas, NV
Posts: 22
Default

BigJohn and JonJay,

Done - I got the master switch wiring all drawn out by hand now (I can follow it at least). After tracing everything, I do indeed have two contactors in parallel. And two master switches as it turns out. The only unique utility of this setup, as far as I can figure, is if I lose just one switch or just one contactor, it all still works. Neither "master" is working reliably, so I think the root of the problem is a 2nd master contactor failure (assuming one failed long ago and was never needed or noticed).

But, now that I've figured out how the wiring really is wired, on my next trip out I'm going to need to check each part of the line, from the master switch(es) on to ensure connections are solid. Maybe I'll need to R&R the master switch and one of the contactors, but we'll find out next weekend at this point.

Thanks all for the thoughts!
-sumo

Quote:
Originally Posted by BigJohn View Post
Sumo,

There seems to be quite a bit of confusion in this thread about the configuration of the high amperage side of your electrical system (battery, solenoids, starter, master switch and associated wiring.)

In my experience it is futile to guess at what is going wrong unless you understand the design of the system. My suggestion is that you take the time to trace out the wiring and draw a simple schematic that you can then use to help you isolate the cause of the problems. This should not be a really big task, since you only need to know how the system works at the "front end". If you don't have the skills to do this yourself I suggest you find someone to help you that is knowledgeable about electrical components and wiring.

Working on experimentals that someone else built can be frustrating, especially if the documentation is thin or non-existent. Ask me how I know!

Figure out the electrical system in your airplane, and then take a step by step approach to diagnosing the problem. Good luck!

John
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  #19  
Old 01-08-2019, 07:16 PM
acehiggy acehiggy is offline
 
Join Date: Jan 2016
Location: Granville, Ohio
Posts: 8
Default

So you have three contactors then ... two in parallel for the Master (12v power bus) and a third for the starter motor? Do you have an electrical diagram you can post? Something doesn't sound right.

You mentioned when cycling the Master Switch, you got various outcomes. Therefore it makes sense you might have a faulty master switch. The solenoids & contactors can all be easily checked with a multimeter for proper operation.
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  #20  
Old 01-08-2019, 07:41 PM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
Posts: 3,343
Default

If wired as described, easy to check. Just turn on one master switch, check operation. Turn it off, repeat with the other master switch on.

Parallel means that either master contactor will power the plane and the start contactor.

My bet is on flaky ground circuit from the master switches.

Charlie
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