My 96 mx5 did not have cruise so I bought all the parts needed to install cc once installed it is not working. How can I diagnose my servo or my switches to see if they are bad. I can turn it on and the switch lights up red but it will not engage when I set the speed.

 

There's little rubber plug that the clutch switch hits under the dash when the clutch is up (not depressed). When that plug gets old, cracks, and falls out the clutch switch goes in the whole the plug fell out of. The ECU thinks the clutch is always down and won't turn the cruise control on. That would be my first guess. Crawl under the dash and see if the switch is hitting anything when the clutch is up.

I taped a penny over the whole and it worked until I got a chance to get the plug from Mazda.

 

i have checked this and unplugged the clutch switch.