Along with the 'vette, a Factory Service Manual (fsm, alias "Helm
manual") is a good idea.  Check eBay or order from <www.helminc.com>.

C4 cruise control doesn't resemble that in other GM cars.  Early C4s had
it integrated into the dash display along with the signals to and from
the engine control module -- '96 is probably somewhat different.  The
'96 FSM will give you all the circuitry, troubleshooting 'trees' and
test measurements.  Even if you don't do the work yourself, the info
will help your mechanic fix the problem.

Here's one for less than $ 60 -- a bargain:
<
http://cgi.ebay.com/ebaymotors/1996-Chevrolet-Corvette-Factory-Shop-Manual-2-Vol
umes_W0QQcmdZViewItemQQcategoryZ34215QQihZ012QQitemZ220128175661QQrdZ1QQsspagena
meZWDVW

or
< http://tinyurl.com/28d7cg >

--
pj

This is a complex system that requires an electrical schematics to
diagnose correctly. Some simple things to check, which you have
already started, if these are ok than you may need a professional to
fix it. Check the fuse, the power, and continuity at the vacuum pod
switch and the 2 part brake light switch behind the brake pedal. Get a
friend with a similar model to compare it's operation to yours. My
guess would be vacuum.

Last but not the least important, check to see if the CHMSL (center
high mounted stop light, third brake lights) are working. Seems the
cruise circuit uses the CHMSL bulbs for a ground or at least part of
the circuit, if one is out the cruise control won't engage in some
cases.