Thanks Chris,

i thought this was the case when i was dead with no juice!

Ron,

thanks you for the wiring diagram references, this makes it clear now. Actually what i did was to try to wire the tach externally out of the car to confirm it was working, when i cranked the motor sparks flying everywhere and burn smell. The first place i went to was fuse box to check all of them, 3 and 4 did not look fried, i would say more old and corroded, so i replaced for good measure.

with regards to the condensor, i believe i should have said open resistance, not as you quite rightly pointed out open circuit

next steps:

will add a wire to complete the circuit to test i have spark and nothing else has been fried,

step2 - wire in new tach permanently, hopefully in my test i only fried the old tach and of course my new to me tach works!

thanks so much all for your valuable information as always

Rob