Furnace Problems

Just a quick update, I have passed all these suggestions to the new owner. I have yet to hear back from him. I'll update with what he found out when he lets me know. Thanks for the ideas.

on his thermastat if the heat pos. is on the bottom left the hi/low
knob has to be on the top right pos.if it's in the bottom pos.the
blower will come on burner will come on and go right off blower will stay on.

I had my brand new TT do the same thing which wow go figure but it turned out to be the ignitor. or it could be the thermcouple.....

I had a similar issue where the furnace would blow only cold air. I spent hours and hours with a long jumper wire and determined that a wire had to be broken. I followed the bundle from where the wires came from under the wall where the thermostat was and found that the bundle was chewed by mice or squirrels. They only went through one of the many. I fixed the wire and all was well.

Check for obstructions in the burner tube? Maybe spider web or some insect nest there?

Sometimes there is enough residual gas in the lines to operate a burner on the stove for a minute or so even with the gas valve closed. I'd suggest to him to leave the stove top burner burning for a few minutes to be SURE the new LP is flowing from the bottles he just filled. Also help him be certain he OPENS the valve very slowly so it doesn't shut down after sensing a sudden pressure drop. Make sure he also knows how to use the regulator if he has an auto switching system. Might also instruct him in checking the exhaust port on the furnace to be sure it isn't blocked by mud duber or birds nest etc. If all of that checks out it's likely a furnace malfunction. If he's not connected to 120 volt power then it's possible that a little thing like a low battery (causing the blower to NOT produce necessary air flow to operate the sail switch).

You didn't mention the brand of furnace but if it's an Atwood the OFF/ON switch can sometimes be difficult to operate as it's very small and tucked out of the way. Without it being turned to on the thermostat will not start the furnace.

Just a few ideas to consider.