No Amps Showing on Skyview Screen

[Raymo]

The shunt is normally installed such that, once burned out, the alternator would no longer charge the battery or supply power to the main bus.

I thought its primary purpose was to burn up if the alternator malfunctioned with an over-charge, supplying too many amps to the system.

 

[ned]

A shunt is a calibrated resistance device with enough capacity for required amperage. Unless it is severed, it will still work. However, if the calibrated area has any burn on it from the short, the calibration has been violated. It may still have continuity but the resistance would be affected so the amperage would still show, but not accurate.

 

[swatson999]

The shunt is normally installed such that, once burned out, the alternator would no longer charge the battery or supply power to the main bus.

I thought its primary purpose was to burn up if the alternator malfunctioned with an over-charge, supplying too many amps to the system.

Isn't that what the (usual) ANL *current limiter* is for, not the shunt?

OP: did you do a continuity test on the wires from the shunt to the EMS?

 

[DonFromTX]

See my comment #19 re wires from shunt to EMS.
Larry I think you nailed it, the shunt material received a short that burned a small piece out of it. I am guessing that somehow that altered the process it is supposed to do. My friend has a couple of new in the box spares, I am getting one of them tomorrow to test out.

 

[ned]

If it is not burnt completely in two pieces, it should still indicate charge/discharge.

 

[DonFromTX]

I originally thought the same Larry, but some searching on the internet about shunts would indicate possibly otherwise.
I am hoping someone from Dynon with superior knowledge will chime in here on this. If they don't, I will do a substitute shunt drill Monday and find out for myself.

If it is not burnt completely in two pieces, it should still indicate charge/discharge.

 

[DonFromTX]

This is the spot that shorted out to ground by mistake. See the semi circle discolored in lower left of photo;

 

[swatson999]

If it's that wire at the bottom of the picture, then your crimp is incorrect (there should not be strands of wire sticking out of the end of the terminal like that...either the wire was stripped too far, or the crimp is mostly on the insulation, not the wire). Those also look like the plastic style of ring terminals, not the higher-quality nylon ones. And there should be, at least on the correct terminals using the correct crimping tool, TWO crimps...one for the wire, one for the insulation.

 

[Dynon]

The fact that the voltage test you did railed out the reading means that those wires are able to sense the differntial voltage. So there's something else going on.

The entire metal bar of the shunt is a mass that is calibrated (by the amount of material in it) to drop a very small amount of voltage. The Dynon shunt is 1mV per amp of load. If it's damaged, but there was still substantial connectivity in that bar, you would get wrong readings - higher if anything - but it would still read.

If it failed in a way that you weren't getting a voltage drop, you also wouldn't be able to flow the current of the load through it (IE, that bar would be physically broken). Your devices connected through it.

Are you sure that you actually have load going through the shunt? Is the shunt on the positive side of the electrical system?

 

[DonFromTX]

Everything except the starter is going thru the shunt, I have it installed so that I will get alternator charge showing as well as the discharge stuff, directly out of your installation manual.  Just to eliminate the shunt itself, I am going to bypass it with a brand new unit and see what happens. Position A from your diagram.

 

[swatson999]

Out of curiousity...do you have TWO wires coming out of the shunt from each tap for the EMS?  I.e., 3 wires in total (1 big one to the battery or alternator, and 2 small ones going to the EMS and...somewhere else)? A total of 6 wires?

 

[DonFromTX]

Well my face is red, but I got it "fixed".  I had realized that when I made the check with the battery, I did it on the EMS side of fuses.  Decided to run a continuity check of the wires from the shunt to the fuses, they turned out perfect.  Then just to be able to say I did it, I put the ohm meter on the fuses - BOTH were open!  I have no idea how they got blown, I just bought them and installed them a couple of week ago.  Anyhow, new fuses, amps are working like they should.  I did not do a runup test yet, but feel sure it is all fixed.  I am now a happy camper! Thanks everyone for the help, and especially DYNON who came to help me as usual!

 

[swatson999]

What sort of fuses are you using and where are they? How are they installed?

Glad you got it sorted out. Not to be a pessimist, but you may want to try to figure out why they both blew in the first place...get to a root cause, so it doesn't happen again.

Anyway, happy you found what was up!

 

[RV711AC]

It appears that the ring terminal you used is oversized for the screw size. I would also suggest that your load not be connected to the same terminal. The input and outputs of the shunt should be on the large terminal and only the measurement connections to the EMS on the sense terminals. Look into AMP PIDG ring terminals, much better quality with a metal wire support and nylon insulation.

 

[swatson999]

It appears that the ring terminal you used is oversized for the screw size. I would also suggest that your load not be connected to the same terminal. The input and outputs of the shunt should be on the large terminal and only the measurement connections to the EMS on the sense terminals. Look into AMP PIDG ring terminals, much better quality with a metal wire support and nylon insulation.

Vastly oversized, I'd say. Looks like a #8 or #10 ring terminal (and as I mentioned above, improperly crimped and as you mentioned, not really aviation-grade PIDG or equivalent).