furnace not heating well

Typical response. At this point you will need to open things up and find the issue for them.

May need to remove the furnace and get a small mirror to look into some of the ducting. Open any access panels as needed.

Post some pictures for best guidance.

Thank you all for your responses. Does anyone have a Cougar by Keystone? We have taken the rig into the dealer twice to be worked on under warranty. They say that they have checked all ducting and that everything is connected properly and there are no kinks or problems. However we tested the unit and it still took over 4 hours to increase the temperature from 44 to 70 and this morning the room temperature only increased 6 degrees in one hour. Hoping to find someone with information on Cougar to compare. Thanks again!

Not out of line IMO, depending on the layout/design of the TT. We have a 29' TT and our furnace also takes a long time to heat up and struggles to maintain a decent temp. in the 30s.

If you have an enclosed underbelly, the furnace is blowing a LOT of air into the space below the floor which then ends up directly outside. The furnace needs make-up air so air gets sucked inside from the outdoors via roof vents and cracks & gaps in windows, doors and the floor. It is just not a very efficient setup but is the norm out there. I blanked off the ducts into our underbelly space as an experiment in the first year of our trailer and it kept the inside warmer but the floor felt cold to the feet.

We have one 4" duct that goes down into the underbelly space then comes back up in the kitchen. It loses some heat while passing through the underbelly space. You could check to see if you have something similar. I was planning to insulate our duct.

We did complain about our furnace and the dealer replaced the sail switch under warranty but it made no difference. Since you have a new TT under warranty, I would the dealer to check it out in any event.

TTs are generally not insulated very well, esp. in the ceiling space where there will be gaps and voids and compressed insulation (reduces R-value). In our TT, down each side of the ceiling against the outer wall, there is no insulation about 6" wide the length of the trailer. The manufacturers don't care if it's done right, and they can claim the ceiling is insulated regardless.

We actually don't use our furnace anymore and didn't use it once last year in nearly 60 nights of camping from early to late season. Last year I installed a permanent recessed electric heater in each of 3 rooms/areas totaling 1750 watts and it works great.

Definitely sounds like something's wrong, maybe you have a loose or pinched duct somewhere. Almost sounds like the duct work isn't connected well at the furnace. Make sure you're getting good airflow from each duct. With an interior temperature of 36 degrees, my furnace will get up to 68 in about 30 minutes or so and my trailer's longer.

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Not normal.

Probably restricted or disconnected air distribution.
Can you tell if the burner cycles while the fan continues to run?

My plenum in the floor was collapsed as part of the original build. Eventually I added two additional ducts and the heat comes very fast now.

Read other posts where the tubes are just disconnected and the heat does not go into the living space.

Mine will go 50 to 70 in maybe 20 minutes (guessing).

Suggest you look in the bays where your duct work is probably routed. I found two duct hoses disconnected and the basement was very toasty. Check each heater outlet for somewhat equal air flow between all of them.

My furnaces will heat up the rig in minutes.

When the outside temps are in the 20's, our rig will heat from 40 to 65 in about 45 minutes.

Not normal at all. I'd suspect a blocked or detached duct.