Older Westinghouse HVAC package, blower won't come on (low speed not working)

Hi everybody, searched but couldn't find this problem on equipment this old. house built in 1976, I think this is original equipment. Westinghouse model 1D036**AAON rooftop mounted HVAC package unit. Natural gas heat, electric A/C. On the model # , not sure if those are zeroes or ohs. The asterisks are extremely hard to make out, maybe AT, maybe A1, might be only one character. So I call for heat, it fires and burns for a few minutes, then a slight hum for about half second, and it all shuts down. Blower works fine for A/C and manual. I thought it might be the relay, 84-10103-301E, so I replaced it with Supco 90293. Purchased from ebay seller, New Supco 90293 Relay 8400 Series SPDT 16A 24V 90293 | eBay (http://www.ebay.com/itm/121259289804). Still no low speed blower. I've tested Cam-stat FALTS37C-13T-120-170 and it seems to be functioning properly. I pulled the two leads that go to the blower/fan relay. then powered the unit up, called for heat, and after a bit, got continuity at those two terminals. Tested the capacitor on the blower housing, rated at 5uf, tested between 5 and 6 (don't remember exactly).