I Appear To Be Going Backwards

[redhead]

Firstly, my disclaimer. My forte' is not electronics. Old school here. Speak to me in words of one syllable please, I'm trying to understand from a real info deficit.

We have an (old) ComNav 2001 autopilot and a (newish) Garmin 700 series chart plotter. Both are showing my direction as 340 degrees when actually I'm pointing about 170 - and yes - I can see that it's the exact opposite of reality.

An old fisherman told me I have to "flip the black box under your main compass in the binnacle" but that info just doesn't tell me what, where, why, when and how.

Sorry if this is a first grade question, but that's about my level of experience with electronics.

As always, Thanks!

[sailormed]

I think the old fisherman is referring to the electronic compass that your autopilot is using to "see" what the heading is.
Looks something like these:

[redhead]

Found the box - (thanks for the pix). Just hoping I can do no damage, working on the underside of an old oil filled compass about 12" diameter. Fingers crossed, I'm going in!