I have an older (35+year old) Bryant furnace, it has no apparent model #. Just a unit # 85BA88 H8AJ9732. When I started it up for the season it fails to work off thermostat. I can start it manually and when it heats up to temp level fan starts. There is no power coming to thermostat from the furnace fan control box. Is there a set of scematic prints and or a work manuel available. Or any other info that may help?

I have an older (35+year old) Bryant furnace, it has no apparent model #. Just a unit # 85BA88 H8AJ9732. when I started it up for the season it fails to work off thermostat. I can start it manually and when it heats up to temp level fan starts. There is no power coming to thermostat from the furnace fan control box. is there a set of scematic prints and or a work manuel available. Or any other info that may help?
When you say you can start it manually, what are you doing jumping the wires at the thermostat - if you are check or replace thermostat - if you are putting 24V directly to valve - if you are check wiring to the thermostat ( cut / or loose connection) if this is a powerpile type (because of age) you will have to check the millivolt and the drop across the valve. There are different ways of wiring 24V through controls at that age of furnace but it is basic and you should be able to follow it - just do not bypass safeties or controls and if it is a millivolt system it would be better to get a older tec or replace the unit (furnace) but that is your decisson and the advice of a tec. - the furnace as gone longer than expected and there could be issues cracked heat exchanger that can be proved if there is. Let us know - Hopefully Helpful.

Sorry I missed the part where you said no power coming from the control box ( fan and limit control) the limit switch is either open or the wire is loose. Replace the fan and limit if it is the same control or replace the limit if it is separtate. But you should still get the heat exchanger checked.