Trane natural gas heater (uplow gas fired, single stage, fan-assisted combustion system)
13 years old
+I have 2 identical systems and one does not work

Furnace does not cut on.

The diagnostic LED on the control unit blinks continuously slowly indicating no call for heat, but I have power to the thermostat and to the control system

Interior circulation fan does run when I cut on the Fan auto to fan on switch.


Any place on the internet I can find a diagnostic procedure?

Mitchell

Try jumping out your t-stat for a call for heat if it starts your t-stat is bad , or maybe the programming isn't set correctly , if that doent work try jumping the heating circuit at the furnace , if it starts the t-stat wiring is faulty , if it still doesn't start , post again

That furnace should have a White Rogers (50A50-... ) PC board. Jumper R to W at the board. Did the light start to flash rapid? Are you sure you have voltage between R and C on the board?