I have a 71 Deville - the AC unit is currently disabled due to burnt out clutch on compressor. The heater works, but the controls aren't controlling the functions properly! The heater control valve that allows coolant through the heater core is stuck open - and the diverter for the defroster doesn't divert.
no matter what the control lever on the dash is set to (auto, fog, ice), the heat comes out thru the floor vent. Makes it hard to drive on a cold day. Read in a post here that the A/C needs to be up and running for defrost to work properly? Local mechanic says that when AC is repaired to change out the system from old refrigerant type to new one, R 12 or something like that. That is looking like a 500 -600$ bill - I guess new compressor, hoses, whatever. Pretty sure part of the heater control issues due to vacuum probs. There are 2 vacuum hoses go from engine compartment thru firewall to heater controls. One is disconnected in engine compartment, when you take the golf tee plug out of it it has suction. The other hose appears to be connected on both ends. Any ideas greatly appreciated,

That quote from the the mechanic sounds about right, probably on the lower end. You dont necessarily need a new compressor, you can buy the clutch seperately at just about any parts store, however it is still fairly pricey and difficult to replace without the right tools. Hoses will run you about $70 a piece, the control valve will be about $40. All of these parts can be found at oldairproducts.com... do NOT use their online catalog, use their downloadable PDF catalog oldairproducts.com/shop/pdfcatalog.php... the PDF is MUCH more accurate with part numbers and cross-referencing. I have purchased all of the parts I have mentioned above, from them. Their parts are a little pricey, but very high quality, its worth it.

Now As far as what your describing about the controls not working, it COULD be the control head but more likely the vacuum mechanism that is controlling the flow of air is a little on the fritz. This unit is located on the top of the fiberglass box on the firewall. I would suggest having someone you know look at it or having Tim from cadillactim.com take a gander at it since he specializes in that sort of thing.

- Jeff

thank you jeff, that really helps out. dc