As you've been told, lots of things in the path between what's
happening and where it may have started. To isolate some of them out:


1. First try it in ROLL mode. If it still fails, then it's almost
certainly in the "computer" (the black box with the ROLL knob on it).
See if you can get the ROLL knob to have ANY effect in this mode.

2. If it works in ROLL mode, but not in HDG, then try bypassing your
NAV coupler. [This just requires unplugging two cables and plugging
one back in.] You also likely have an HSI - NAV adapter that could be
bad.

3. If the info from your AH is bad, then it will roll no matter what
(but you might be able to offset it, or at least slow it down, with the
ROLL knob in ROLL mode). Those Tyco (AMP) connectors are not very
reliable. Try plugging and unplugging the one between your AH and your
"computer" several times (and make sure it is plugged in good and
locked).

After all that, if even in ROLL mode it insists in rolling
oncontrollably, then you've got a bad computer. You might check for
broken wires on the rear connector housing, or even removing and
re-inserting it a time or to - but most likely it needs to go back in
for service. Century no longer services them, but several other places
do. It's just some simple analog transistor discrete stuff... nothing
high tech.