I hooked up a Honeywell WiFi thermostat last fall. There is no C wire in the furnace & the Honeywell rep suggested I wire up a small separate transformer with new wires going to the C and RC terminals (no jumper between R and RC) on the new thermostat. Heat worked fine all winter & I just switched the thermostat over to cool, but the AC will not come on. "Cool on" is flashing on the thermostat but there is no fan or compressor action.
The furnace is a 1986 Trane model BLU162E960B1. Natural gas - forced air. AC is much newer. The transformer is wired up for 24 volts.
The existing wiring includes a G, W, Y, and R. The C and RC wires go to the small (doorbell-type) transformer. There is no C wire marked on the furnace wires or on the schematic.
What am I missing? No help from Honeywell.