Quote Originally Posted by 36 sedan View Post
Spikes usually take the sensitive components out completely ceasing to work at all from that point on.

Intermittent electronic problems are almost always caused by a bad connection on or at the circuit board. Most times it is a poor solder connection of a component to the board or a damaged trace, sometimes it is a cracked circuit board.

Also you should check with your States consumer affairs, your State may give you legal rights beyond the manufacturers warranty.
I think your analysis is right, and at this point if the fix is not obvious I'm hoping for an offer of a new unit at or near cost. What you say about the consumer affairs office is a good thing to remember, but in this case I'm only looking at a nominal $100 instrument, and looking at the hole in the dash will get old really quickly, and going through the State would likely be an extended process.