Don't know if my problem is the same as everyone elses, because it's not related to engine speed. Our '82 300D has sporatic heat. It's been a while now that if she does blow heat, it's luke warm and usually quickly changes to cold. It doesn't matter what position the climate control is in, whether it's defroster or regular blower. Last week I was lucky enough to leave the defrostor on while uncovering the car of snow and heat was blowing out the whole time, until I was almost done wiht the trip it was turning to luke warm. Is this a monovalve problem too? If so, what and where is the monovalve. My dad took the climate control panel apart and she looked brand new inside. Good contacts and all. What you guys think?