Spray some glass cleaner (foamy type) around windshield and use a blow gun to blow air from inside out and if the windshield is leaking you'll be able to see it.
Also if you have perhaps a remote start or alarm somtimes when they run wires through the firewall into the rubber grommets, people don't seal them properely and I've seen those leak also.
Also if you have perhaps a remote start or alarm somtimes when they run wires through the firewall into the rubber grommets, people don't seal them properely and I've seen those leak also.
