Continuing Ammeter Woes

[pvalovich]

RV-8A, ~400 hours, AFS-4500.

After an early spring flight, noticed the ammeter - shunt current source - had stopped working (horizontal dash instead of a digit below ammeter bar). Checked settings, connections, wire continuity, pins. Problem magically corrected - for about ten minutes, then returned when I pulled plane out of hanger. Made me suspect broken wire or intermittent connection. Ran new wires, replaced pins, replaced shunt connectors - same problem. Will appear fixed then problem arbitrarily but quickly returns. Been wrestling with this for months.

Don't think it's a software issue. I'm suspecting an intermittent connection - inside the box. Otherwise, I'm out of altitude, airspeed and ideas.

Anyone have any suggestions?

[Shawn McGinnis]

I would start by entering calibration and looking at the value that is displayed in the shunt calibration page. The -- is out of range. Another option is the install a backup hall effect ammeter to see if the shunt is malfunctioning.

[pvalovich]

I would start by entering calibration and looking at the value that is displayed in the shunt calibration page. The -- is out of range. Another option is the install a backup hall effect ammeter to see if the shunt is malfunctioning.

Don't understand the "shunt malfunction" comment. All other aspects of electrical system working fine - if shunt is malfunctioning wouldn't there be other indications?

[Shawn McGinnis]

Malfunctioning used for its meaning of equipment that fails to function normally or satisfactorily.

As stated before check the calibration page to see what AD_VALUE your EFIS is reading.

Shunt Reading Diagnostics:

• < 650 Amps #1 + Disconnected (ORN/GRN)
• 2500 at 0 amp
• 2600 at 5 amps
• > 4000 Amps #1 - Disconnected (ORN/PUR)

[pvalovich]

Shawn - took photos of my 4500 display and the ammeter shunt calibration page. Couldn't figure out how to include them in forum response.Sent them to you via separate email to the AFS info email address. Did you get them?

[Shawn McGinnis]

ammeter shunt calibration

Given the picture that you send your AD_VALUE is showing 4095 which is either the case that your Amps #1 - is disconnected (ORN/PUR). If you disconnect the Engine Harness from the back of the unit does that number return to ~2500?

[pvalovich]

Rechecked all components yesterday - shunt integrity, connectors, wire connectivity, pins. Got 11.63V to the pin. Reconnected everything with EFIS not screwed into instrument panel - ammeter indicated proper operation. Shut everything down, secured EFIS, turned power back on - problem has returned. AD- values same as before - 4095 when inop.

On my way to Eglin AFB in FL. Will call tomorrow to see if I can get a Hall Effect sensor.