Hi. My 2002 XC70 heater stopped working unless the temp is set to 78 or higher. A setting of 70 used to be just fine, but now it needs to be set at 78 or higher. Three trips to the dealer and he is unable to solve the problem. Any ideas? Thanks.
Re: Heater won't heat until temp set at 78 degrees F. (dhm)
I had a problem with heater only heat when on MAX. This problem ultimately traced to the temperature sensor (behind the 3 slits) on the ECC not working. Easy diagnostic is "can't hear faint fan noise" behind the 3 slits for a minite or so after the key is taken out (or plugged in without turning it). Read the section "Jammed ECC Temperature Fan spindle" in the link in my signature below.<p>Hope this is your problem. I think it is a common problem after a few years. Dirt and thread jams the fan that pulls air accross the heated wire to sense interior temp.