I have a 1984 with similar problem. My HSI spins 180 degrees out (off heading) when in slaved mode. I replaced the KMT-112 (located in left wing, 3rd inspection plate out from gear door). The inspection plate was riveted (not screwed) which made swapping out the 112 a challenge. Alas, the problem is not fixed...
Any updates or advice as to what to do next?
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