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Pcflip · 12-23-2008, 08:48 AM

I have a Surburban SF42 furnace that has been giving me problems for the past several years and have ran into a problem I can't seem to fix and need advise. Here is how it started on cold evening the furnace would not fire, you could here the ignitor firing but would not light. I was on my way to Ohio for a job so I stopped into a RV repair shop and the Tech removed the unit, bench fired it, and reinstalled it. It worked fine and he informed me that sometimes the gas orfice gets a piece of trash/rust and will not let the gas pass to fire. So for several years now everytime I relocate the trailer I have to remove the unit, disasemble, and clean the orfice. This has worked fine untill the last time I worked on it and now I have a new problem. If the unit does fire and run it roars loud and backfires/pops.
I have tried several things but the only way I can get it to fire now is to hold my hand over the air inlet on the unit and it will fire and if I leave my hand over the inlet and restrict the air flow by 50% it will run fine with no loud noise and no popping.
I seem to think now its sucking too much air, but from where. Or have I bent/broken something removing and reinstalling it.
Any suggestions.
Please Advise

Fyrzowt · 12-23-2008, 08:52 AM

While I can't help you with your furnace problem, there are many here who will offer ideas for you. Hopefully soon....
I noticed that this is your first post, and wanted to welcome you.
Dave

HowieE · 12-23-2008, 10:25 AM

It sound like you are playing with a BOMB. I am not one that would normally suggest going to a shop, because I have little or no faith in them, but in this case I think you need help. I would look very hard for input before committing to a repair shop.

There is no way the heater could have INCREASED the air it is taking in. For what ever reason your are gas flow is reduced and thus the need to reduce the quantity of air to maintain a flame.