[stackj]

Don't overlook any areas where recent repairs have been made on the tach system.

I had a problem with the gauge cluster that Keven mentioned in an earlier post inthis thread. After several months of troubleshooting this intermittent problem, I found a sharp point on a solder connection I had done. This connection was 'protected' by heat shrink... but not well enough. The point was able to poke through the heat shrink just enough to cause an intermittent ground causing me to loose oil pressure indication on the front engine.

Unless you particularly want to get digital tachs for your bird, I'd avoid trying to get a field approval. You need a cooperative inspector AND IA. The way people file suits, I can't blame them...but inspectors don't like to stick their necks out by approving one time installations.

Those who have installed the gauge cluster that I designed will tell you the most difficult part has been getting inspector approval. My inspector asked that I not share the form 337 when I give out details on the installation and I have honored his request. (I may need him again).

Good luck.

By the way, my manuals only cover up to the 73 skymasters. If you have a schematic of the circuit you can share, I'd be glad to look it over, but from the symptoms you describe, it could be almost anything, including two different failures (the front engine tach was acting up way before the rear one).

It is possible you or your mechanic could have caused the problem for the rear engine while troubleshooting the front engine.