IFD540 & Stec-55x Glideslope Wiring

I have the above with an NSD-360A HSI installed in April; GS arms but won't couple. HSI GS indications normal. ILS & GPS with vertical guidance both don't couple. I thought at first I just didn't have the parameters just right, but after more than a dozen precision approaches I've definitely got the flying part down. It looks like the 540 has 3 GS output wires and the Stec wants 4. Has anybody had this problem or know of a likely fix? Thx.

Does your 55x have autotrim?  BH

Reason I ask is that there are some installations where auto trim is required
for GS coupling.   Not an issue here, it's something else.   BH

jonesronc wrote: My current aircraft doesn't have autotrim, but neither did my previous twin with a -30, and it coupled fine. Al at Avidyne tech support said go from GAMA 429 to GAMA 429 with Graphics/INT on the ARINC config page, but the aircraft couldn't hardly keep course with that.  S-Tec said go with the plain ARINC 429 format.  Which format are y'all using? Ron

Regarding -30, come to think of it, you're right - I would set trim for Ground Speed/2 *100 = fpm and down I'd go; I was confusing that with a TruTrak I was flying at the time.

Regarding ARINC, why did Avidyne think it was an ARINC issue when I called them?

Ron

Fixed the problem; one of the high density pins on P1001 had lost its lock and was pushing in when the radio was loaded into its tray.  Reset the pin and all works now.  yay