content: Like the other users that have commented here, I was initially very disappointed. However, as I was grumbling and about to throw away the user guide, I decided to (gasp!) read it. Turns out the on/off switch is a 3 position switch, marked with 3 symbols: A Roman numeral I, A Roman numeral II, and a 0 (Zero). So, I thought that zero was OFF, and number I would be LOW and number II would be HIGH. Turns out that number I is AIR ONLY and number II is AIR + HEAT. After trying it out on II, it was nice to discover a decent amount of heat coming out. I installed 3 of them on my daughter's Blazer, since there are three large pieces of rear glass that are always fogging up, and these 3 units perfom pretty well. Not hot enough to pose a fire hazard, but warm enough that after 5 minutes of operation, there is about a two foot circle of clear glass, and here in Alaska, that isn't too shabby.