Abnormal RPM,Amps Readings : Where to Start Trouble shooting

Bardample

I love flying!
Joined
Aug 18, 2013
Messages
28
I fly a vfr Vans RV7a with a Classic 10 Skyview, now about 8 years old with 400 hrs on the clock. All readings have been stable until today.
I had an over speed indication of 2720 rpm on take off on three occasions today.I had previously adjusted the governor some time ago to keep the rpm max 2700 . This overspeed indication today is new. On climb out at full power the rpm gave readings of 3000-4500 for a-time before returning to my set rpm of 2400. My initial thoughts were a prop overspeed , but this was obviously incorrect.

A short time later in the flight with no increase in electrical load, my ammeter readings went from normal cruise 8-10 amps upto 30-40 amps for some minutes. My ammeter measures my B and C 40 amp Alternator ( about 2 years old) output to battery plus Buss . There is a B and C ext regulator installed. I have also installed a Monkworkz 30 Amp generator ( with reg) so that it is wired in parallel with the main Alt. The Monkworkz Gen is set to only provide power if the system voltage drops to 13.7 v. I monitor the Monkworkz current input into the Buss on the Skyview screen , so this is usually 0 amps , when the B and C does its job. As I have an Earthx 680 battery, I am used to seeing upto 40 amps of current at at start up only( the battery is ' hungry') , but not at cruise or climb.

I switched off my main alternator, but the Skyview amp reading still continued to read high 30-40 amps. I noted that after turning off the main alt, the Monkworkz amp out rose from zero to 9-10 Amps, as one would expect if the main alt was not providing power to the system. After a few minutes when I switched the main alt back online , my readings became 'normal'.

As the above abnormal readings are erroneous, I need advice about the cause and where to start looking.

thankyou in anticipation
Jeff R ( Australia)
 

skysailor

Active Member
Joined
Oct 17, 2008
Messages
596
With all of these symptoms I would be looking for bad grounding. Check all connections but pay very close attention to the grounding strap between the engine and the fuselage. Check fasteners are tight and remember to pull on the wire as it goes into the connectors. I would also recommend you check the path for the ground from the airframe to the ground bus to which the Dynon is tied.
 

Bardample

I love flying!
Joined
Aug 18, 2013
Messages
28
Thanks for you advice. These were my initial thoughts, but as I had just completed a 'very thorough ' annual checkup , I thought there may be something else that may be lurking. I shall do the rounds as you suggest.
I once before had erroneous Ammeter readings and found that was fixed when I replaced the 1 amp fuses used inline for the amp readings from the shunt. Jeff R
 
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