Suburban furnace blower issue

It can also be caused by impatience.. Many home furnaces when the burner cuts off the blower cuts off.. (Some newer ones it runs a bit longer)

RV furnaces, it runs a bit longer.. If it gets to 2 or 3 minutes you have a problem but at one minute I think you are ok.

IF the furnace has a "Blower only" mode (Which I would like to have) then it could be the T-Stat,, Otherwise it is the relay (or it's driver) on the control board that need attention. (New control board) If you have to put in a new board.

Consider Dinosaur Boards.. I really like the one I put in my Atwood.

There is two styles of time delay relay setups. One has it adjacent to the fanh housing. It is normally black about 1 inch square with four connectors. The other style is on the circuit board.

Here is a link to the service manual; LINK. Page 23 gives the sequence of operation when you turn on your furnace. Looks like Old-Biscuit hit the nail on the head. The module board is part no. 520820.

The model # is NT-20SE and its a 2010 Catalina.

If disconnecting t-stat wire to furnace didn't stop the furnace blower from running then the problem is with a shorted timed delay relay/circuit

What model & year of Suburban furnace?

thanks for quick response. The T-stat is a heat only. There is no fan on/off switch. I disconnected the T-stat wire and blower kept running. The T-stat is a Suburban with 1c20-130 inside the cover.

If your t-stat controls A/C & furnace the FAN position controls only the A/C unit fan.

Furnace blower running continuously is caused by two things.
Bad t-stat....furnace wires/contacts shorted together
Bad timed delay relay. If you have a stand-alone relay it can be replaced...if relay is part of circuit board then board has to be replaced.

Remove your t-stat (front cover) and disconnect furnace wires.
If furnace blower stops running them replace the t-stat----now would be a good time to go digital. Hunter Digital T-stat (one that is battery operated) is a frequent choice for upgrade. $25 at Wlamart

See if your thermostat has a fan switch that says "Auto/on". Turn it to auto.
Make and model of thermostat would be help full.
You could disconnect one of the wires at the thermostat. If it shuts off then it is bad thermostat.