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gremlins

chevytoo

Member
A flight in my RV-9A the other day, after take off I see on the altimeter I am climbing at an unusual high rate. Field elevation is 200 Ft. I am 1 mile from the airport and at 3000 ft. The look out the window tells me I am only at 1000 ft. I asked the tower my altitude and they came back I was at 900 ft. Obviously something wrong with the altimeter. The airspeed and rate of climb are working properly. I was cleared back to the circuit and landed uneventfully. On the ground my altimeter is showing 1500 ft. This is the second Falcon altimeter to fail in this way. This altimeter has 5 hours and over a year since new. The first one never got in the air since new but almost 5 years old. I taped off the static ports to paint the aeroplane. Several weeks later I removed the masking on the static ports, the altimeter was reading about 3500 ft. Field elevation 400 ft. I tried disengaging the barometric scale and resetting the elevation but the pitot static tester said the altimeter did not pass. I have ordered a new United TSO'ed altimeter. My RV-9A has all steam gauges.

Next problem. I noticed in flight a while back that the ammeter ( Vans steam gauge) was reading 10 amps charging. After shut down and the master switch turned off the ammeter still showing 10 amps charging. I pushed the aeroplane in the hangar. I then turned on the master and now the ammeter is showing 10 amps discharge. All other switches are off. The next day I go to the airport, turn on the master and the ammeter reads "0". turn on the landing light and it reads a discharge. Landing light off and the ammeter reads "0" again. I start the engine (starter turns the engine 2 blades and starts). ammeter read charging and the charge rate slowly dropped. I noticed later the charge rate about 8 amps. The volt meter reads 14 volts. Other than gremlins, anyone got any ideas what is causing the ammeter to act this way
Ray
 
Did you check your pitot / static lines, that there is no blockage and that plumbing is correct to all gauges? Sounds like you may have a blockage in your static line into the ALT ( critters maybe?). Also if you have an AOA and have the ALT plumbed to that line, would result in some wonky readings.

Ammeter sounds like it is hooked up to measure current between the battery and master solenoid. This should show a negative value when master is turned on & engine not running. Should show a positive when alternator is re-charging the battery after an engine start, or a negative value when the alternator is off (or not working) while engine is running.
As for the needle not centering, have you tried tapping it, maybe a sticky needle?
Most common Ammeter shunt installation location is on the B lead from the alternator before it connects with the main bus, this reads alternator output.
 
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