There is a long thread in another post that is pretty old with no real solution to this problem of the TruTrak autopilot pitching up with the push to talk button. It is an isolated problem but, if it affects your installation it is a real bear to isolate the source. After many attempted fixes that did not work this one did.
I followed the link as previously posted on the filter that goes between the head and the harness made by Digi-Key, purchased it, installed it in 5 mins, and it solved my pitch up problem with my PTT. I believe my problem originated with my using a single shield coax instead of a double shielded coax like RG400 on my radio antenna. I did route my coax completely separate from all other wiring, but apparently the Garmin puts out a lot of RF. Here is the link and the part cost $27 plus shipping. Good luck!
http://parts.digikey.com/1/parts/1599616-filter-male-female-adpt-25pos-fce17-b25ad-250.html
Don
RV7
PHX
I followed the link as previously posted on the filter that goes between the head and the harness made by Digi-Key, purchased it, installed it in 5 mins, and it solved my pitch up problem with my PTT. I believe my problem originated with my using a single shield coax instead of a double shielded coax like RG400 on my radio antenna. I did route my coax completely separate from all other wiring, but apparently the Garmin puts out a lot of RF. Here is the link and the part cost $27 plus shipping. Good luck!
http://parts.digikey.com/1/parts/1599616-filter-male-female-adpt-25pos-fce17-b25ad-250.html
Don
RV7
PHX