Testing the unit is another issue. Haven't had ice on the windshield to test. I originally just had the passenger side work not the drivers side. Right down the middle of the windshield I would notice half was working. I tried the steam off a hot cup of water. That didn't really show anything. I do notice now is when I activate the heater for the windshield, it definitely draws power to where my rpms dip for a good second while at idle. Praying for some morning frost....