Originally Posted by Superstroker1
When hooked to shore power I can hear the sounds your saying and hear the furnace light
When not hooked to shore power just using the battery’s you can here the blower turn on but not the clunk sound of the gas or the click click to ignite
Good, making progress. For safety reasons, there is a fin in the blower air path. If there is sufficient air flow, the fin (called a sail) moves to one side, out of the air path and actuates a switch (sail switch),which allows the gas valve and igniter to actuate.
The blower is a typical DC motor, speed dependent on voltage. That's why everyone was after you to check the battery voltage; if it's too low the blower speed will be low and the sail switch won't actuate.
We haven't asked, but we are guessing you have the common Suburban SF-series (SF-25, SF-35, etc.) furnace. Is that correct?
What we need to do now, just to be sure, is to check the voltage at the furnace. It "should" be the same as at the battery, but let's be sure, if you can do it. An easy way to do this is to remove the thermostat cover and measure between the OFF and HEAT terminals of the switch on the thermostat when the switch is in the OFF position.
A more difficult way would be to measure between the red and yellow wires going to the control board. If you can see the wires going into the furnace but no connections, you could skin a little insulation off the wires, make your measurement, and wrap the bare spot with electrical tape.
If this measurement is above 12 volts, then the control board is suspect.
EDIT: Or there is insufficient airflow at 12.6 volts. Only sufficient airflow when the voltage is even higher. These motors are not supposed to be lubricated and it's rare to hear that one has bound up. But we frequently hear that there's an airflow restriction.
Go to the outside furnace vent and make sure that wasps or spiders have not built a nest in the intake or exhaust port.