I have to 'fess up, btw, while whining about my heat - I am running Sierra A/F (or it's successors). This might make a difference, eh? But thanks to about 1,500 suggestions, I'm gonna try a new thermostat, flushing the core again, and a new core, in that order. Or I could swap on parts from the '85 one by one until it fixes it... -- Huw Powell