Every propane appliance in a coach meters its fuel through one small part. It is a brass orifice, called a burner jet by Dometic, threaded into the outlet of the gas valve ahead of the burner. It is solid except for a single hole drilled through the center, and at a given supply pressure that hole alone sets how much gas reaches the flame. Suburban's on demand manual puts the relationship in one table: the ST-42 is rated at 42,000 BTU per hour on a 0.037 inch orifice, and the ST-60 at 60,000 BTU per hour on a 0.047 inch orifice. Ten thousandths of an inch of diameter is the whole difference between them. Tank water heaters run a smaller hole again, a number 61, supplied as kit 180323 for the 161255 gas valve. Furnace orifices range from a #55 on an SF-20 to a #50 on an SF-42. None of it is a wear part. All of it is calibration.
A correct LP flame on an RV appliance is small, steady and blue, with a defined inner cone sitting close to the burner ports and barely any yellow above it. That appearance means the gas collected most of the air it needed before it ever reached the flame, which is the whole job of the burner venturi. A lazy yellow flame that licks and wanders is reporting a wrong mixture, not simply a dirty appliance. Yellow light is incandescent carbon: fuel burning without enough oxygen in the right place, glowing instead of combusting cleanly. That is why soot is the finding which ends the visit rather than one detail among several. Suburban treats it as urgent in its own words, telling owners to shut the unit down on sight of soot because soot forms whenever combustion is incomplete and is a visual warning the appliance is operating unsafely. The color is the reading. Everything after it is deciding which side of the mixture failed.
Two different faults get described with the same sentence, and telling them apart is most of the diagnosis. A restriction at the orifice sits on the gas side. Less propane passes, and because the gas jet is also what drags primary air into the venturi, the air falls away with it. The ratio therefore stays roughly correct while the flame turns small, weak and slow to establish. On a direct spark unit it usually ends in lockout instead of a bad flame, which is what Suburban describes as flame out protection, shutting the gas off when low propane pressure or a burner fault kills the flame. A restriction in the burner tube, the air shutter or the intake screen sits on the air side. Gas arrives at full rate, air does not, and the mixture goes rich and yellow. Put plainly, a plugged orifice tends to mean no flame at all, while a plugged air path means a bad one.
The classic RV burner blockage is not carbon at all. It is a nest. Mud daubers are solitary wasps that look for a sheltered tube of roughly the right bore, build mud cells inside it, and pack every cell with paralyzed spiders for the larvae to feed on, a habit the Missouri Department of Conservation sets out in its field guide. The black and yellow mud dauber, Sceliphron caementarium, and the organ pipe species are the ones doing it in propane bays. A furnace burner tube, a water heater intake behind the door screen and an absorption refrigerator flue are precisely the cavity they hunt for. They are not following the odorant in the gas. They are following a dry, quiet tube that nothing has used lately. A coach left standing through a hot Gainesville or Clermont summer, furnace idle and water heater switched off, hands them months of undisturbed access to all three.
Manufacturers converge on this instruction, and it is the one owners break most often. Dometic's refrigerator installation manual is blunt: never use a wire or pin to clear obstructions from the burner jet because damage will occur, and do not attempt to adjust the burner jet. Suburban permits no cleaning or adjustment of its on demand burners at all and routes the work to a service center. The reason is arithmetic rather than caution. A drill bit or a torch tip cleaner does not lift a blockage so much as recut the hole, and flow rises with the square of diameter, so a hole opened ten percent passes roughly twenty-one percent more propane. The appliance then overfires into a heat exchanger and a vent sized for its rated input. Scorching, sooting and a cracked exchanger follow in that order. A blocked orifice gets replaced, and Suburban's warranty language already treats cleaning or replacing one as routine maintenance.
Owners call about the symptom, never the part. The usual description is that the refrigerator will not hold on gas, the furnace runs and runs without heating, or there is a scorched smell and a dark streak above the water heater door. Our technicians work from the outside in: door screen and intake, then burner tube and venturi, then the orifice, then electrode gap and flame sense. Gas pressure comes last on purpose. A manifold pressure reading is what separates one sick appliance from a whole coach running low, and a low figure at every appliance points to two-stage regulator replacement rather than burner work. Our service call covers the trip out and the first hour on site at the rate in the pricing table on this page; anything past that first hour is quoted and approved before we carry on. Ignored, a sooting burner consumes its own flue and then the exchanger.
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Call 888-759-1438Small, steady and blue, with a sharp inner cone near the burner ports and barely any yellow above it. It should sound like a low even hiss rather than a flutter. Any lazy orange tongue, any wandering, and any black streak on the flue or the appliance door means combustion is incomplete. Suburban's own guidance is to shut the appliance down when soot appears and have it looked at before running it again.
No, and the manufacturers say so directly. Dometic's installation manual instructs owners never to use a wire or pin to clear an obstruction from the burner jet because damage will occur, and not to attempt to adjust it. A wire burnishes and enlarges the hole rather than clearing it, and the damage stays invisible until the appliance starts sooting. The correct repair is a new orifice, which is a low cost part.
It would produce more heat and an unsafe appliance. Gas flow scales with the square of the hole, so a modest reaming can add a fifth again to the burn rate while the heat exchanger, the vent and the combustion air path all stay sized for the original rating. Suburban's parts manual lists the same burner assembly, 010865, under both the SF-30 and the SF-35 furnace. Only the orifice number separates them.
Because the nesting season here barely closes and the coach sits still through the worst of it. Mud daubers want a sheltered tube of the right bore to fill with mud cells and paralyzed spiders, and an idle furnace burner tube, a water heater intake and a refrigerator flue all qualify. Storage months with the appliances switched off give them uninterrupted access, which is why the fault surfaces on the first cold night.
Clearing a nested burner tube and fitting a new orifice usually fits the first hour. A burner assembly or a gas valve is a parts order, so we confirm the fault before quoting the repair.
Every figure on this page comes from a manufacturer document or a standards body, not from another repair site. Here is where each one comes from.
| Item | Price | What it covers |
|---|---|---|
| Service call | $299 | Includes the trip out to your RV and the first hour on site |
| Work past the first hour | Quoted after diagnosis | We tell you what it will take before we carry on |
| Parts | Quoted per job | Special-order parts may need a deposit before we order them |
| Written estimate | No charge | You approve the estimate before any work starts |
The service call covers the trip out to your RV and the first hour on site. Anything beyond that depends on what we find, and we quote it and get your approval before carrying on.
The price ranges on this page come from our own recent jobs across Florida, not from an industry average. What you pay depends on the rig, the parts it needs and what we find on site, so we give you a written estimate before any work begins and you approve it first.