Porsche Repair: heat wont shut off, heater control valve, engine coolant

Question
I have a 1989 944 NA.  The heater won't shut off but keeps blowing slight amounts of heat into the cabin even with the fan switch turned all the way down.  How should i solve this issue?

Answer
Hi John,

Here's the first place I'd check:

There is a heater control valve in the engine compartment that diverts some of the hot engine coolant to the heater core to warm you up on cold days.  The valve should prevent hot coolant from getting to the core on warm days.  Check the following web page and look for the photo link under the heater valve heading to see what you are looking for.

http://www.pelicanparts.com/catalog/shopcart/944M/POR_944M_VENTht_pg1.htm#item1

Dave