Furnace starts out great & then later not?

smkettner wrote:

Blanco1 wrote:
To be honest these last two post are much more technical than I understand?

Yet appreciate it, in time I 'll start understand your lingo. :)

RV furnaces have a high temperature limit switch to prevent the box around the furnace propane burner from overheating. Generally the normal airflow should keep the burner box cool enough to operate continuously.

Due to general poor engineering and workmanship it seems to be fairly common for RV to not have enough airflow through the furnace. This causes the box around the burner to get too hot. There is a "high limit switch" that turns off the propane burner when this happens. The fan continues to run and cools the burner box. Once the temperature drops to a safe level the burner will come back on.

My furnace does this. Fan runs continuous but the burner flame cycles on for about 2 minutes, off 1 minute, on 2 minutes etc. until the RV gets warm and the thermostat says to quit.

My ducting in the floor was collapsed when built. I discovered this with a mirror looking down into the ducting. Unfortunately mine was long out of warranty when discovered.

You may have a similar issue and eventually the propane burner does not relight so it blows cold air until morning.

What you need to do is sit and focus on the sounds the furnace is making when it fires up. You should first hear the fan and then the burner a few seconds later. Then you need to continue to focus for a least 10 minutes and listen for the burner to cycle off and back on. I find it difficult to notice the burner going off with the fan noise etc. but when it relights the burner the sound is much more obvious.

If the burner does run continuously you just eliminate this issue and we move to the next....

Good luck.

As I stated before My heater high limit switch opens with every duct opening removed and the basement wide open with wind at 50f blowing through it. The opening area is twice of what Suburban says is needed. Every gas cloths dryer made uses the same snap switch to control dryer temperature. As every rv I have ever worked on cycles the hi-temp switch, I wonder if Suburban even knows how their heater is designed. Dinasour says that the 6 time out is designed into the original boards. I will agree most rv,s could use better ducting. -*