lutful... of ideasPremium
The house was built in 1989. YORK's model number label may be hidden behind the original installer's support label - I will check.
However, I know there is no draft inducer fan because I stood and watched the call for heat cycle. The faint pilot flame magically becomes a huge hissing flame. There is no fan noise at all just flames. The blower does not actually turn on until a minute later.
I checked the schematic again and it seems the heat call always runs the blower on HIGH. Only the manual fan call runs on the MED setting.