[DeTomaso] (no subject)

[JDeRyke at aol.com]

William, a bum connection might do this. Its simple enough to run a separate 
patch-wire from the distributor to the tach and check for bad connections. But 
I suspect its the tach itself. I've been inside my unit and these things are 
pretty simple devices, so if you're willing to dig inside the tach's case, the 
1"x 2" circuit board can be inspected. In my case, it was a precision glass 
resistor that had split in two. We desoldered the resistor from the little 
board, read the color code and substituted an identical 1% resistor. Reassembing 
it, the tach worked perfectly- and still does 7 yrs later. I wrote of this in 
the Spring '99 P.I magazine. 
To get inside, you must use a fine flat-blade screwdriver to lift the 
backside of the swedged bezel a little at a time. The good news is the bezel is not 
100% swedged and you only need work about halfway around to remove it and the 
glass. Then a couple of screws losen the tach guts and out she comes for a 
look-see. Good luck- J DeRyke