PilotPete
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- Mar 16, 2011
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I noticed yesterday when checking my pitot heat current draw, that my ammeter is not showing the correct load.
Embarrassing as this may be, I never really paid much attention to the actual amperage readings before, just looked for changes when things were turned on/off to confirm that they were working.
Background:
PA32R-300 Lance
EI VA-1A digital volt/amp meter - has intenal shunt
Set to 12V - reads voltage correctly (batt and alt)
Load current with engine on ~0.7A
Load current when pitot heat turned on ~1.2A
So that would mean 1/2-amp for the pitot heater - don't think so!
The pitot mast and pressure mast both get hot - just replaced the and tested the heaters individually so I know they're good - expect to see ~16A on a 20A breaker.
Checked the wiring at the back of the VA-1A and it has two large (#4 AWG?) cables attached to the two lugs (as it should). Circular connector with power/signals is also looks fine.
First thought is that when the VA-1A was installed, the old shunt wasn't removed, so only part of the load current is going through the meter.
Did a search today and couldn't locate a shunt, but haven't traced the wires completely from stem to stern yet.
Any thoughts as to what's going on?
I presume that before this device was installed, the ammeter on the engine cluster was used. Does it require a shunt, or do the heavy wires from the alternator get connected directly to it?
Embarrassing as this may be, I never really paid much attention to the actual amperage readings before, just looked for changes when things were turned on/off to confirm that they were working.
Background:
PA32R-300 Lance
EI VA-1A digital volt/amp meter - has intenal shunt
Set to 12V - reads voltage correctly (batt and alt)
Load current with engine on ~0.7A
Load current when pitot heat turned on ~1.2A
So that would mean 1/2-amp for the pitot heater - don't think so!
The pitot mast and pressure mast both get hot - just replaced the and tested the heaters individually so I know they're good - expect to see ~16A on a 20A breaker.
Checked the wiring at the back of the VA-1A and it has two large (#4 AWG?) cables attached to the two lugs (as it should). Circular connector with power/signals is also looks fine.
First thought is that when the VA-1A was installed, the old shunt wasn't removed, so only part of the load current is going through the meter.
Did a search today and couldn't locate a shunt, but haven't traced the wires completely from stem to stern yet.
Any thoughts as to what's going on?
I presume that before this device was installed, the ammeter on the engine cluster was used. Does it require a shunt, or do the heavy wires from the alternator get connected directly to it?
