I have a single screen HXr with GRT Autopilot and the "Original" dual AHARS.
A few months ago (after ~2 years of trouble free AHARS) I was flying in IMC at ~5000 feet, about to enter the approach, on AP, and I entered a diving left turn. This wasn't "uncommanded" because the EFIS showed me suddenly at 12000 ft in a hard right turn. I disconnected the AP and hand flew the approach on my back up EFIS (Dynon D10A) and the 480 HSI. I actually flew the missed (runway made) and stayed in VMC for the ride home. Here I made a mistake. Instead of trying to select 1 AHARS at a time, I left it on "Dual" and used my VPX to power off the AHARS 1 at a time. Ultimately, neither worked for the flight home. When I next flew, I determined that only AHARS 2 was bad.
After OSH (a lot of troubleshooting, but no answers), I sent the box back to GRT for "repair". They sent me an entirely new Dual AHARS. When I connected it up, AHARS "1" came up (on the ground) in a steep right turn (not a steady one). A week later, I powered up to fly to an Avionics shop for some work and both AHARS came up ok. ~20 min into the flight (VMC), I again went into a left turn. This time, I switched between AHARS and they were BOTH doing similar gyrations (not exactly the same pitch or pattern). When the avionics tech powered up the panel (I hadn't told him about this), he called to tell me that both AHARS were acting crazy and showing the plane flying all over the sky. Later, after powering down and up again, only AHARS 1 was bad.
Note" no movement of aircraft when AHARS starting up, until aligned.
At the Avionics shop we have:
- switched cables (no change. still top AHARS in box is bad)
Checked/cleaned the cables-no change
put a meter on each power pin (24.7V on each) and checked each ground wire (no V and appropriate resistance to ground block)
pulled all the power pins from the VPX and run power directly from the (28v) battery (no change)
confirmed that Pin 10 (OAT) is empty on both cables
Note: the 2 AHARS share nothing (except the ground plane they connect to). They are each on a separate Bus in the VPX (separate processors and power supplies).
Any ideas out there??