During my engine restoration last winter, I add to my 69 RS the optional instrument pack, sold by heartbeat Camaro.

I also installed a Pertronix from eBay.

I drove the car for about 1 month then smoke came out from the dash and the tach was gone. I installed another repro tach, and it last for about 2 hours then burned out as well. What's the problem ? The tach is connected to the negative pole of the Pertronix, is there an incompatibility?

Any idea is appreciated ? Thanks to all!
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Not sure if this would affect the tach, but for the Pertronix, you did abandon the factory resistance + coil wire and run a new full 12 volt supply wire, right? Depending on which model Pertronix you got, powering the coil with the factory resistance wire can actually destroy the ignition module.