factory tach

i just converted over my 396 from points ignition to HEI. the car ran great for one day, then it died in my driveway (luckly for me)as it turned out the moduel went.i have a factory tach which i connected to the terminal next to the power terminal on the coil. (coil on cap type HEI) Some people told me that the tach could have shorted out the moduel. Is this possible and does any body know if the factory tach will work with HEI