The monovalve got it. I had ordered a kit when I first bought the car, "just in case". After I got home from work, I poked around my junk in the garage and found it. Took not much time at all, after moving the diagnostic port out of the way. Blows hot air now, and, for the record, the vents in the center are not supposed to blow heat. I found this info in a wacky place - the owner's manual!
And I have flushed and replaced the coolant just this past spring, but that is good advice I agree.
Thanks for the help!
1989 560SEL (172k)
1989 325IC (122K)
2004 Suzuki Volusia LE (3500 miles)
2005 Yamaha Road Star (20 K miles)