amp meter reading higher than normal, changed one electric gauge.
I changed my turn and bank to an electric ai and have noticed my ammeter reading much higher. Dont know if its coincidence are not.
On a night flight, with lights on (not landing light) and everything running, I seemed to show around 30 amps on the ammeter.
When I was flying in Saturday night, I had all on, including my landing light and fuel pump, and it was pegged out to 70 amps. Turn the fuel pump and landing light off and it came back to around 50.
Does this sound normal after adding an electric ai?
Re: amp meter reading higher than normal, changed one electric gauge.
Is the starter Bendix still engaged? With the mag switch off try turning the prop just a little if you here the ratcheting sound of the bendix it never disengaged after your last start. If it is engaged the ammeter will show an excessive charge.
Re: amp meter reading higher than normal, changed one electric gauge.
Ok, some updates.
Starter is not engaged.
With everything off (avionics) its showing 35 amps. The electric AI is the only thing hardwired (I believe)
Turn on the nav lights, goes up about 5
Turn on the Avionics goes up about 10
Turn on the Fuel pump goes the remainder off the chart
The panel gauges and landing light just continue.
The circuit breaker never pops.
I installed a new plane power alternator and zeftronics reg. not too long back and didnt have any problems after installing.
One thing Ive always noticed is I hear a small (every so slight) whine when its under a good load. When I peg the meter that same whine comes on, but the meter would usually be at around 40 with everything on.
Re: amp meter reading higher than normal, changed one electric gauge.
I wouldn't worry about the whine. I'm just saying it's probably not a clue.
The ammeter indicates current by measuring the voltage drop across what is called a shunt. You might check the connections of the ammeter leads to the shunt. I don't see how you could really have all that current going someplace and nothing is burning.
Re: amp meter reading higher than normal, changed one electric gauge.
Jason,
It's just an idea. A loose or dirty connection at the shunt could cause the meter to read high. It's at least worth checking and I think it would be easy.
Re: amp meter reading higher than normal, changed one electric gauge.
Have seen this before it was a bad battery. When the battery starts to go south the battery itself with no load (nothing on) demands up to 20 Amps on its own with. This can be agrivated the battery was just serviced.
Re: amp meter reading higher than normal, changed one electric gauge.
With everything off (avionics) its showing 35 amps. The electric AI is the only thing hardwired (I believe)
Turn on the nav lights, goes up about 5
Turn on the Avionics goes up about 10
Turn on the Fuel pump goes the remainder off the chart
The panel gauges and landing light just continue.
The circuit breaker never pops.
If my fuzzy math serves me we have 35 +5+10 = 50, at least another 20 amps when you turn on the fuel pump. I am not an electrician but I would probably be suspecting the fuel pump. that seems like a lot of amps. Anyone have an idea of what the fuel pump should draw?
Re: amp meter reading higher than normal, changed one electric gauge.
Jason,
I think maybe the message got confused in the retelling.
The alternator's rectifier has a bridge circuit, similar to a wheatstone bridge, to convert AC to DC. I wouldn't expect a bad rectifier to cause high current through the ammeter, but I suppose it's possible. It would explain that high pitch hum you mentioned.
That corroded resister on the bus sounds more like the shunt I was referring to. It's not a bridge however.
Re: amp meter reading higher than normal, changed one electric gauge.
Gotcha.
So just to explain to the electrically challenged, is the corroded part causing the amp gauge to read high (but everything act normal) or is it actually putting a high amp load on the system?
Re: amp meter reading higher than normal, changed one electric gauge.
Jason,
If your problem is really a bad shunt, then it's just causing your ammeter to read too high. I'm not real confident that replacing the shunt or cleaning it up will solve the problem. But since you haven't found anything else wrong, that is worth a try.
I would have bet on the weak battery theory. But if the battery is OK then the shunt is a possible source. Other possibilities might be that the regulator is set too high, or weak fields in your alternator.
Re: amp meter reading higher than normal, changed one electric gauge.
Jason,
No, I don't believe I'd replace the battery if it tests good under load and cranks the engine well. Somebody mentioned above that you should find out how many amps the AI should draw. Maybe it's actually much higher than we expect.
If you have a split master switch you might be able to disconnect the battery from the circuit and see what that does to your load current. I have a solid switch so I don't really know how that split switch works.
Is your voltage about normal? If it's adjusted too high it would certainly drive up the current. Look on the voltmeter and you may see a small white line in the green section which I believe indicates where it should be.
Re: amp meter reading higher than normal, changed one electric gauge.
Not sure what type of plane you have, but there are two kinds of "load meters" (ammeters). One kind has heavy terminals and heavy gauge wires going to it and passes all the current thru it. It reads current directly and they rarely go bad. The second type has dainty wires because it uses an external shunt (a heavy-duty resistor) that handles the current and just reads the voltage drop across the shunt (remember Ohm's Law?). If that's what you have and the shunt is bad, the meter will read a higher voltage drop than it should. A good A/P should be able to add a second, known-good ammeter in series to do a functional check of the plane's meter.
You should NEVER operate an alternator without a load (battery) as if you do they can generate quite high voltages. Most split master switches are interlocked to prevent you from shutting off the battery with the alternator active. By the way, turning off the Alt switch doesn't disconnect the alternator output...it just shuts off the field circuit.
Re: amp meter reading higher than normal, changed one electric gauge.
I believe all Pipers have those "dainty" leads going to a shunt. If the ammeter reading is actually erroneous, the shunt would be the most likely source. It sounds like the mechanic is swapping out the shunt.
Re: amp meter reading higher than normal, changed one electric gauge.
Jason, This may seem too simple but have you tried switching the Turn Coordinator back out to the original one and seeing if things go back to normal? Just a thought.
Re: amp meter reading higher than normal, changed one electric gauge.
SOLVED!!!!
before ordering the shunt, they tried (like mentioned above) a second gauge. When the bus was fully loaded the gauge was pegged over 70 amps, the new gauge read around ~30.
Pulled it and check again against a different gauge with the same results.
