I am sure you are working on an old car, as these analog signals (high beam indicator etc )are no longer present in can bus based cars.
If you want to count "high" pulses, use digital read and connect like this:
12v signal -->10k resistor--> arduino digital pin<--100k resistor<--vehicle ground
I see no chance to burn arduino board if connected like this.
arduino uno board has voltage stabiliser and two filter capacitors, this setup survives automotive applications for few years already (my experience).