Furnace Burner

The burner section of the furnace exhausts to the exterior of the rig. That is normal.
You said the furnace cycles on and off, how often? This should happen about 6 times per hour. There is an adjustment on some thermostats to change cycling but it also changes the temperature on/off times. It is the Attenuator. This is on mechanical thermostats.
It is possible that the furnace is shutting down via the over heat sensor. Furnace over heats sensor opens then cools off and restarts. Could be caused by restricted air movement with in the furnace or ducting in the rig.

It is always nice to have brand/model so better/direct answers can be provided.


Generic answers.

Furnace is 'limiting' (caused by high limit switch operating due to lack of air flow, high gas pressure or faulty limit switch)

Furnace sail switch is not staying made up due to low 12V DC power.

Furnace has a cracked heat exchanger......

Provide more info....brand/model and what is happening (fan continues to run, burner shuts off/fan stops, burner lights then drops out etc.)
More info provided the better ideas as to problem. Especially when one can not see/hear furnace operate.

Good question that I would also like to hear about, I noticed mine does that too when the heat has to run for a good amount of time, I would say 30+ minutes, like when first heating the trailer up. The fan will run continuously but the burner cycles.

What is a lot of heat? The heat should be venting out of the vent as part of normal operation.