Almost exactly 1 year ago, I bought an aftermarket hood tach for my 68 firebird 350 from The Parts Place on Ebay. The tach worked fine up until a week ago. I first noticed the malfunction right after I washed the car (by hand, not through a carwash). The car has an upgraded HEI on it, so the tach is connected to the distributor through the “tach plug-in” on the distributor. When I turn the ignition on (engine not running), the tach indicator jumps up to about 6000 RPM. When I start the engine, the indicator is all over the place, mostly on zero. While driving, when I back off the accelerator, the needle rises (acts like a vacuum gauge). This morning I noticed that there is condensation behind the lens and there is no response at all in the tach. I drove the car yesterday and it has been sitting in the garage overnight. Any suggestions or ideas?
