I have two problems - they both came up almost simultaneously.

Background - I recently had the dash apart to work on my dash lights.

Problem 1 - My tach started acting crazy - jumping around like the tach cable wasn't engaging. I figured it was loose. It wasn't. I took it off and reseated it with no improvement.

Problem 2 - I was driving on the highway and my speedometer acted crazy for a few seconds and then went completely dead. It seems as though the cable was engaged. I haven't tried reseating it yet.

How do I troubleshoot these problems? I'd like to know if this is a problem with the cables, with the gauges, or with the connections.

Disconnect the tack at the distributor, pull on the inner cable and see if it comes out in one piece. Same for the speedo, disconnect at the tranny. I've had this happen to my TR250 and the cables were broken. Why it happened to both in close proximity of time is very odd.

Thanks for the tips. FYI - I took the speedo and tach to a friends house. We tried running them with good cables (he had some spares lying around) and a drill. The speedo was frozen - it needs repair work. The tach seems fine. However the tach cable came out without detaching it from the engine. So the cable is a likely candidate. It could still be the drive gear in the engine block, but I'm going to try swapping the cable first. Its hard to tell why things go at the same time on these cars. Sometimes they just do.