Checking voltage at 3 wire plug on the back of lock cly for the exciter [transponder reader] . Unplugged, Grd 0 volts, ref 5 volts, supply 12 volts. Plugged in grd 0 volts, ref 3.64 volts, supply line 1.25volts. THE 1.25v seems wrong and can not find a value. ... Login to read more.