Furnace - propane stop/start during its on cycle?

time2roll wrote:
My OEM ducting was inadequate. I added 2x 4" additional ducts and the furnace works so much better with tons more heat and the burner stays on the entire cycle.

I believe OP has had this RV for a while and this IS a recently new "symptom".. If I am correct, that would make the assumption of not enough ducting not much of an issue unless a new blockage has been introduced (like a blanket covering a register?)..

dougrainer wrote:
"Regulator malfunction can result in higher propane pressure to the furnace which affects flame size.. Check the burners on your stove, flame should not be excessively high and should be all blue".

This will not work. The Stoves/Ovens have their own regulator set at 10 inches water column. So if the LP regulator is too high this regulator will fix that for the Oven/Stove. Doug

RV furnace gas valve also has "it's own" regulator same as a home gas furnace and even home gas stove and oven, but those also can be affected by the incoming gas pressure if it is too high or too low..

Cat hair and lint blocking incoming air?
Its just a bunch of slats in the furnace box

My OEM ducting was inadequate. I added 2x 4" additional ducts and the furnace works so much better with tons more heat and the burner stays on the entire cycle.

"Regulator malfunction can result in higher propane pressure to the furnace which affects flame size.. Check the burners on your stove, flame should not be excessively high and should be all blue".

This will not work. The Stoves/Ovens have their own regulator set at 10 inches water column. So if the LP regulator is too high this regulator will fix that for the Oven/Stove. Doug

How long between flame on and off? YES, it is normal for a LOT of RV's. Because the OEM did NOT install the ducting to Furnace install specs. This causes the Hi Limit switch to kick in and out during the cycle. The furnace overheats due to the lack of adequate ducting to remove the heat from the burner chamber. So, as other have suggested, an RV furnace it is NOT a good idea to clock off some duct covers to get more heat to another area. Even blocking just one duct cover will cause this. Most common cause is the round 4 inch flexible duct hose in kinked or smashed somewhere inside the floor or cabinets, if the ducting is installed to furnace specs. Doug

Get the battery charging, low battery voltage for sure can cause the furnace fan to not run fast enough to keep the sail switch on continually (one of the safeties) causing burner to turn on/off intermittently..

Lol..
You guys may be geniuses.

I am not at RV at the moment, but both of your ideas may be correct.

I have a 6 yr old that keeps tossing her blanket down near the back vent.
I keep yelling and picking it up.

Last night I got home to.. no batteries being charged.
(I will post on this too.. GFI breaker in breaker box)

So I turned everything 12v off except furnace last night so furnace would last the night.

Make sure output vents are not closed off, make sure return is not blocked or if someone installed a filter thinking it’s like a home furnace.

JimK-NY wrote:
This topic has come up several times in the past. Some responses have recommended checking the ductwork to be sure there are no restrictions.

I am of the opinion that this is normal operation for some RVs and for some furnaces. My burner definitely cycles on and off numerous times when raising the RV temperature by several degrees. This has always been the case and my rig is almost 20 years old. I have never timed the cycles but I think the burner probably runs for 3 or 4 minutes and then blows air for almost that same period of time before the burner starts again.

I am not sure I would call short burner cycle "normal", none of the RVs I have had have done that.. My current TT I have taken the temp from 40F to 70F and never once had the burner turn off.

Perhaps normal for yours if the RV manufacturer did not follow the furnace manufacturers minimum ducting requirements which would not be unusual..

Furnace manufacturers do list cold air return minimum opening and also minimum hot air outlet requirements in square inches for each BTU size of furnace.. Wouldn't surprise me if the RV manufacturer failed to follow or exceed the minimums..