Absolutely need one. Can't clear ice/frost off windshield without one and I am not going to peer through a thumb size clearing in windshield. My truck has the original heater, never even had to have it flushed. Took truck out for a blast on the highway at -30 C to test and more than enough heat. I replaced the 6V heater motor with a stock 12V heater motor out of a 80's dodge van .