Westach Amp gauge

9 posts in this topic

Posted

My Westach amp gauge appeared nonto he working. I checked the shunt by the battery and something didn’t look right with the wiring. Can you see it ???

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Posted

Yep. There is no voltage drop across the shunt the way the it is wired. Your fuselage ground should go to the shunt terminal on the right and the battery negative should be connected to the shunt terminal on the left.

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Posted

Looks like something I would do, but I wouldn't post a picture of it for the world to see :)

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Posted

Close. The shunt read voltage drop between the battery positive and the main alternator wire before the main power buss.  This thing is hooked up totally wrong and missing one leg to the main terminal. 

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Posted

The diagram shows the correct way to wire it. I was thinking you were intending to measure the return current through the fuselage to the battery, and that is why the ground wire was connected to the shunt.

Whatever you do, make sure you protect that positive battery lead. Unfused wires make great arc welders.

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Posted

I’d like to take credit for this bundle of electrical excellence but it was already installed this way then I got the airframe. It’s one of the things I just looked over while putting the rest of the plane together. It will get installed correctly. 

Does anyone else run one of these. How is yours installed?  Location of the Shunt? Wire size to the Shunt?

 

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Posted

The idea behind the shunt is to allow for the shortest possible path for charging current to reach the battery so excessive voltage drop doesn't occur.

The wire size thru the shunt should probably be 12-10 gage depending on the length to minimize voltage drop. So if the run from alternator to battery is short, 12 gage is prolly sufficient. if it is longer something like 10 gage is more appropriate. The wires between the shunt and meter are much smaller. about any size you want to use. The whole purpose of the shunt in the first place is so that you don't have to run the wire carrying the charge/discharge current all over the place up to a meter because that creates voltage drop. So the shunt should be placed wherever that can be achieved.

in an extreme case you could have the alternator and battery only a couple feet apart, but the instrument panel could be 20 feet away. So the shunt would be placed between the alt and batt, and the very small wires can go as far as they need to to display the current flow. This avoids creating excess voltage drop in the charging line.

Does that make sense? 

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Posted

Chris, This shunt it mounted right over top of the battery behind the seat and I assume was suppose to connect to the main battery positive lead.  The other feed line would have to come from the line between the charging system and the main power buss. Wouldn't it be smarter to mount this behind the instrument panel? A short lead from the positive starter poll and another from the main feed wire from the charging system should make for a working Amp gauge. 

OR

Since the shut is mounted nicely behind the seat I could run a jumper to from the battery positive and a wire from the front to complete the circuit.

  

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Posted (edited)

It depends....Do you have a master solenoid? if so where is it located? where is your starter solenoid located? It would be nice if you can take advantage of the heavy gage starter wire if it goes all the way up close to the firewall hot. If you have a master solenoid back by the battery you can't do that. You want to minimize voltage drop in the charging circuit.

There are a lot of good ways to skin the cat but one will be best for your particular setup. That's what you need to figure out.

 

 

 

 

Edited by Chris Bolkan

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