Sounded like $500 to replace that stinkin servo in my car, so I just took two pieces of heater hose and bypassed it. Removed the non-functioning aux coolant pump at that time also. Now I either have no heat, or it cranks hot out the defrost. If I push defrost first then half push in bi-level, I get a mix. Works good enough for me and cost a couple bucks. I made a thread on that a couple years ago with pics, wonder if it is still here....

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Think Alternative Energy!
300CD '80 (now gone but not forgotten...)