RV Repair: backfiring in Suburban gas furnace Model SF-42, wasp nest, gas furnace

Question
The furnace in my 2004 5th wheel makes a loud rumbling noise which sounds like it's trying to ignite.  I can see a flame in the outside vent when this happens.  I am going through about twice the amount of propane I should be using.  It started out occurring very rarely but now seems to be happening quite often.  It's very loud; my neighbors can hear it.  When the RV was still under warranty the dealer said the noise was normal.  Any ideas?

Answer
Hi Vickie, Its not normal. You may have a wasp nest in the burner chamber. Who is the dealer that said its normal?? And If you had it looked at under warranty and it still is not fixed then call suburban customer care. They will have a record of it by looking up the Serial number. They might arrange for you to have it repaired at a real repair shop for free. Good Luck.