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  #1  
Old 04-16-2021, 11:29 AM
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ExtraKatana ExtraKatana is offline
 
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Default Bus Voltage HIGH

I have a call into B and C but I thought I would pull the immense knowledge as I’m sure several of you have the same set up. L-40 alternator and LR3D-14 external voltage regulator.

Bus voltage 13.0 terminal three voltage 13.0 terminal four voltage 11.57. Terminal six voltage 12.86…… That is before I start the engine and engage the alternator.

Within two minutes after starting the engine my voltage slowly creeps up to 16 at which time the panel circuit breaker attached to terminal six engages and takes the field out of the system. I have tried to adjust the very small screw driven voltage setting on the regular with no luck.

Thoughts?
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  #2  
Old 04-16-2021, 11:59 AM
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Default

Measure at the alt itself, should be within .5 of term 4.
Also suggest monitoring reg term 3 when it starts creeping up as that is the sense term.
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Last edited by Walt : 04-16-2021 at 12:05 PM.
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  #3  
Old 04-16-2021, 12:11 PM
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ExtraKatana ExtraKatana is offline
 
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Default

Quote:
Originally Posted by Walt View Post
Measure at the alt itself, should be within .5 of term 4.
Also suggest monitoring reg term 3 when it starts creeping up as that is the sense term.
I did and it is. That test would reveal basically a bad wire or connection. Why would that all the sudden go bad?
I didn’t do all of the Ohm tests like between terminal 6 and the engine case but I did do this one. All of the connections are tight.
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  #4  
Old 04-16-2021, 12:23 PM
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Quote:
Originally Posted by ExtraKatana View Post
I did and it is. That test would reveal basically a bad wire or connection. Why would that all the sudden go bad?
I didn’t do all of the Ohm tests like between terminal 6 and the engine case but I did do this one. All of the connections are tight.
Did you do it with the alt plugged in?
I see bad wiring/switches all the time for multiple reasons (especially cessna style switches and cheap breakers).

And verify the reg case/term 7 has a good ground.
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  #5  
Old 04-16-2021, 12:41 PM
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Default Yep

Alt was plugged in per instructions and ground is good. No Cessna switches here
Going to do an Ohm check this afternoon. Thats all thats left
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Last edited by ExtraKatana : 04-16-2021 at 12:44 PM.
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  #6  
Old 04-16-2021, 01:17 PM
Avanza Avanza is offline
 
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Default ALT PROBLEM

If the problem persist, I suggest removing the alternator and make a new
crimp on the F-connector. Put silicon on so the wire canīt vibrate.
I had this problem.
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  #7  
Old 04-16-2021, 03:10 PM
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Default Tests

An individual at B and Chas been very helpful so far.

I have done the ohms test between pins seven and the negative contact on the battery and the result is .1 with a continuity buzzer. The same test was done between the negative post on the battery and the engine case. .1 again with a continuity buzzer.
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  #8  
Old 04-16-2021, 03:21 PM
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Default Just me

If the guy at B&C doesnt recommend anything further, I would put a voltage meter across the regulator from the bus sense to the ground (on the reg) and see if the voltage changes. That should be rock solid.

If good than there is a wiring problem, most likely either ground or bus sense. By the way, what is on the bus sense circuit?

JMHO
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  #9  
Old 04-16-2021, 03:30 PM
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Default Bus Sense

Is “Bus Sense” the field? From which terminal on the LR3D-14?
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  #10  
Old 04-16-2021, 03:42 PM
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Default

Quote:
Originally Posted by ExtraKatana View Post
Is “Bus Sense” the field? From which terminal on the LR3D-14?
No, not field.

Term 3---goes directly to the buss through a 2a fuse/cb. It is sensing the buss voltage. This is how the reg knows how to tell the alternator what to do.

You can download the info here https://bandc.com/reference-library/ This will be a PDF document. Page E-1.
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Last edited by Mike S : 04-16-2021 at 03:45 PM.
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