FWIW, this sounds very similar to how the climate control in an old Volvo 240 works. There is a rheostat buried deep under the dash, and when it fails you can o

FWIW, this sounds very similar to how the climate control in an old Volvo 240 works. There is a rheostat buried deep under the dash, and when it fails you can only select between ambient temperature air or Swedish Sauna Hot. If you find someone who has done this exact repair before, it will take them about 4 hours. If you DIY it as a decent mechanic, count on spending a whole weekend.