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  #11  
Old 11-08-2016, 03:58 PM
Mike S's Avatar
Mike S Mike S is offline
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Quote:
Originally Posted by 1flyingyogi View Post
But the thing that bothers me more is the 8amp draw when the master switch is flipped (with nothing running).
What kind of switch are you using?

Cessna style split switch------are you only hitting the batt side or also the alt side.

As I recall, a bad diode in the alt can cause your 8 amp draw if you happen to be turning on the field at the same time as the master.
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Flying as of 12/4/2010

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Last edited by Mike S : 11-10-2016 at 03:11 PM.
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  #12  
Old 11-08-2016, 04:34 PM
rv7charlie rv7charlie is offline
 
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Nominal cell voltage for a lead-acid battery (flooded or AGM; same thing) is 2.0 Volts when fully charged. 2.2V per cell is roughly the threshold to *charge* a lead-acid battery.
https://en.wikipedia.org/wiki/Lead%E2%80%93acid_battery
8 amps is quite a bit for 'idle' current, unless you've got a lot of mechanical stuff that's live in addition to the master contactor (1-2A typical).

I'd certainly find that screw. Even if it isn't your current (pardon the pun) problem, it might well be your problem in-flight at some point.

I really don't understand why anyone who's doing their own electrical work doesn't follow the Matronics Aeroelectric list, and have a copy of 'the book'. (It's a free download.)

Charlie
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  #13  
Old 11-08-2016, 05:24 PM
Mich48041 Mich48041 is offline
 
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Quote:
How do I check the master/ start relay?
By measuring voltage drop while the circuit is under load. The greater the load, the more current that flows and the greater the voltage drop, which makes it easier to find problems. You mentioned using a battery load tester in post #1. Disconnect the starter and connect the battery load tester in its place. Energize the starter contactor and quickly check for voltage drops. I say quickly because the starter contactor is not made for continuous duty, and because the heavy load will be running the battery down.
Most people will connect their voltmeter black lead to aircraft ground or battery negative. That works, but an easier way is to connect the voltmeter red lead to the battery positive terminal and test the positive half of the loaded circuit with the black meter lead. Or connect the voltmeter directly across a suspect component like a contactor.
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  #14  
Old 11-10-2016, 02:56 PM
1flyingyogi 1flyingyogi is offline
 
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So I had a bit of time at the hangar yesterday and here's what I found out:

When I removed the alternator from the circuit breaker (disconnected it), the amp draw problem went away! So again, with master switch on (everything else off), my ammeter shows 8-9amps being drawn. With the alternator disconnected from the system, when I flip the master, I only get about a 1amp draw. I was told that I could have a bad diode in the alternator. What do you guys think?

I checked my battery again with a load tester and it seems the battery is fine. After a full charge on the battery tender, voltage shows 13.5volts and under load drops to about 10.8 to 11.1volts. Returning to about 12.5volts after load removed and slowly climbing to about 13.x volts.

After this, I pulled the plane out and tried starting it. I noticed that ALL the nuts holding the wires on top of the plugs were loose! I tightened them all and the engine started up right away! I shut down and waited 10 minutes and it started back up again. So that was the cause of my hard starting problems - I hope??

When running, everything seems fine. Alternator charging the battery (reading 14.0volts, and ammeter shows current going into the battery).

Brian
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  #15  
Old 11-10-2016, 03:10 PM
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Mike S Mike S is offline
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Quote:
Originally Posted by 1flyingyogi View Post
When I removed the alternator from the circuit breaker (disconnected it), the amp draw problem went away! So again, with master switch on (everything else off), my ammeter shows 8-9amps being drawn. With the alternator disconnected from the system, when I flip the master, I only get about a 1amp draw. I was told that I could have a bad diode in the alternator. What do you guys think?


Brian
Yep, diode issue by the sound of it.
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Mike Starkey
VAF 909

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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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  #16  
Old 11-10-2016, 03:13 PM
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LettersFromFlyoverCountry LettersFromFlyoverCountry is offline
 
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The battery you're describing doesn't strike me as a big deal that should cause bad starting.

Have you had a look at your spark plugs lately?
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  #17  
Old 11-10-2016, 05:26 PM
8 ball 8 ball is offline
 
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Location: hilltop lakes' Texas
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Default Starting problem

If a starter solenoid had inadvertently been used instead of a master solenoid would that cause an extraordinarily high amp draw? Just Askin'
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  #18  
Old 11-21-2016, 01:00 PM
1flyingyogi 1flyingyogi is offline
 
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I got some help from another RV guy at my field and tested my alternator and said it had an internal short. So I pulled the alternator and had it rebuilt, but did some research and found that a brand new one at Autozone was only $43, so I bought a new one and installed that (I had to use the old pulley b/c the new one was too small and would spin too fast).

But... problem not solved. When I turn the master switch, the ammeter still shows an 8amp-9amp draw! With alternator field wire disconnected, the draw went away. We tested the alternator again just to make sure and it's a good alternator.

So my friend tells me that the ONLY other thing it could be is the regulator. Here is a photo of my old regulator:

https://drive.google.com/open?id=0B3...jRfRllNdFhONUU

And bought this new one here (which apparently a lot of VAF guys are using). Part numbrer VR730:

https://drive.google.com/open?id=0B3...zV3RC10QWYxNmc

The only thing is I don't know which terminal is used for what. I called the tech line and got a bit of help, but just wanted to be 100% sure before I install it. Can someone please confirm?

Here's what I got from the tech guy at Duralast:

He said that the far left terminal (apart from the other three) is for an indicator light - not used in my application. The next one over is for the "switch battery voltage" - same as my red wire on my current regulator? Next to that is for the "stator terminal" - not used in my application?? And the last one over is the "field winding" - wire that goes on the top terminal in my current regulator that connects to the field on alternator. Is this right??

Thanks again for all your help!

Brian
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  #19  
Old 11-21-2016, 05:16 PM
Mich48041 Mich48041 is offline
 
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When the engine is not running, the voltage regulator will allow maximum field current to flow, usually 3 to 5 amps depending on the size of the alternator. 7 or 8 amps is excessive for the size of alternators used in homebuilt aircraft.
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  #20  
Old 11-21-2016, 08:06 PM
1flyingyogi 1flyingyogi is offline
 
Join Date: Dec 2015
Location: Long Beach, CA
Posts: 370
Default problem fixed!!

Finally!! I was getting pretty frustrated and was going to just give up and pay an A&P to figure it out for me if I couldn't make any progress today. But after installing the new voltage regulator, it worked perfectly. Amp draw now is about 2amps as soon as I turn on the master switch and then settles down to about 1amp.

Thanks again for everyone's input. Now, I just gotta put the plane back together and hopefully go flying again by this weekend!!
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