Furnace won't light

If it has not been used for a while it will take several attempts to light it to bleed the air out of the propane line. Can you hear it lighting and then going out? it will cycle and try to light 3 times then you will have to turn it off and on again to get another 3 times trying to light. The battery also needs to be charged as low voltage will also cause a problem.

Dig into the unit and snap some photos. Often they are little switches that fail. There can also be sensors (for air flow and thermal cutoffs). It would also help to have the model number.

I have a Suburban SF42-Q and it was doing the same thing you are describing. I took it to a repair shop and they replaced the limit switch. Furnace works good again.

The furnace on mine is right under the fridge. There is a vent there where you can go in, remove a cover and the limit switch is there. They cost around ten bucks. You can even get them through Amazon or even Ebay.

Unfortunately you're going to have to start removing panels then somehow remove the furnace to get to the inner works to find the problem. Normally there should be a louvered panel or something similar for supply or return air that can be removed. Many times the panels are held in place with screws or pin nails.

Based on the description I suspect you have a Suburban Furnace that looks something like this -



Without knowing the specific model can't give much concerning procedures beyond what others have posted.

The fan will continue to blow if there's a lack of propane.
The furnace is usually covered by a large intake grill. It will be down low at floor level.

If the fan comes on, but igniter does not click and propane valve does not open, the first suspect is INADEQUATE AIR FLOW to close the SAIL SWITCH.

Low voltage is the most common issue, leading to slow fan speed.

Closed, restricted or crushed ducts can also cause inadequate air flow.

The furnace will be directly inboard from those two ducts. But, I would verify the above before doing anything with the furnace itself.