RV furnace not working: what fails, in what order, and what it costs

RV furnaces fail in a strict sequence, which makes them one of the easier systems to diagnose over the phone. The blower runs, then a switch proves the airflow, then the board calls for gas, then the igniter fires, then a sensor confirms the flame. Whatever step it stops at tells you what is wrong, and the great majority of these repairs land between $200 and $800. In Zephyrhills the furnace is a cold-night appliance that sits idle for most of the year, and that idle time is what breaks it.

Check this first (fifteen minutes)

Turn the thermostat up and listen. You should hear the blower start, run for fifteen to thirty seconds, then a click and a whoosh as the burner lights.
Nothing at all? Check the thermostat, the 12V supply, and the furnace fuse. Furnaces need good battery voltage; a bank sitting at 11.5 volts after a summer on the space will not run one properly, and a control board that took a surge in a summer storm will not run at all.
Blower runs, nothing else? The sequence stopped at airflow proving or ignition. That is the sail switch, a blocked intake or exhaust, the igniter, or the board.
Look at the exterior vent. Mud daubers and paper wasps build in the exhaust and intake tubes constantly here, and a blocked tube stops the sequence. This is the most common cause we find on rigs whose owners have just come back for the winter.
Lights then goes out after a few seconds? Flame sensing, or the high limit tripping because airflow is restricted. Check that interior return vents and floor registers are not blocked by furniture or storage. A flame-sense electrode that has corroded over a humid summer is also common.
Confirm propane. Other gas appliances lighting is the quickest test, and a nearly empty tank on a cold night can deliver poor pressure.

What is usually wrong

Where the sequence stops	Likely cause	Fix and cost
Nothing happens	Thermostat, fuse, low battery voltage	$150 to $400
Nothing happens, and it died after a storm	Surge-damaged control board	$250 to $600
Blower runs, no ignition attempt	Sail switch or blocked intake or exhaust	$200 to $500
Blower runs, sparks, no flame	Gas valve, propane pressure, blocked burner	$250 to $600
Lights, then shuts off in seconds	Flame sense or high limit tripping	$200 to $550
Runs, then cycles on limit repeatedly	Restricted airflow, blocked registers or ducts	$200 to $600
Loud, grinding, or squealing blower	Blower motor or bearings, often rust	$300 to $800
Smells of propane at any point	Stop, shut the gas off, call	Diagnose immediately

These sit on the pricing page alongside the $75 to $150 trip fee and $125 to $190 hourly labor.

Wasps, rust, and the empty summer

Almost every furnace call we take in December traces to the same thing: the rig sat from May to October, and something moved into it or rusted in it. Mud daubers build in exhaust and intake tubes. The blower wheel, the burner, and the electrode sit for months in air with a dew point in the 70s and humidity past 90 percent every night, and steel parts that were clean in April are orange in November. Rodents nest in the plenum too, which is both a repair and a fire concern.

The preventable version costs almost nothing: screens over the exterior vents, and a test run before you need it. Fire the furnace up for ten minutes on a warm November afternoon and the worst outcome is that you find a problem on a pleasant day instead of at 2am on the first cold night. We include that test in an arrival check, along with the water heater, which shares the wasp problem.

The other reason it matters here

New arrivals underestimate Florida winter nights. The average January low in Zephyrhills is around 47 degrees, the winter months are the short cool season the whole snowbird calendar is built around, and an RV is a thin aluminum box with single-pane windows. It sheds heat fast. Winter residents who arrive in November, run nothing but the AC through Thanksgiving, then meet the first real cold snap are the classic no-heat call, and they are all calling on the same night.

Duct losses, and the fix that is not a repair

If the furnace runs correctly but the rig never warms up, it may not be a fault at all. Common contributors: ducts that have come loose in the underbelly and are heating the basement rather than the coach, registers blocked by storage bins, a thermostat mounted on an exterior wall reading cold, and simple lack of insulation. Several of those are cheap to correct and none of them are furnace repairs, and we would rather find one than sell you a part.

What to expect on the call

Tell us where the sequence stops, the furnace brand off the exterior panel if you can see it, your battery voltage, and whether it worked last winter. That usually narrows it to one or two parts before anyone drives out. We work on site across Zephyrhills, Dade City, San Antonio, Wesley Chapel, and Land O’ Lakes, and the appliance repair page covers the rest of the gas and 12V side.

Frequently Asked Questions

My RV furnace blows cold air and never lights. What is wrong?

The blower running without ignition points at the sequence after the fan: usually the sail switch that proves airflow, a blocked burner or exhaust, a failed igniter or board, or low propane pressure. Wasp nests in the exhaust and intake tubes after a Florida summer are the single most common cause we find.

How much does RV furnace repair cost in Zephyrhills?

$200 to $800 covers the great majority: sail switches, limit switches, igniter boards, gas valves, and blower motors. Full furnace replacement is a larger conversation and rarely necessary if the blower and heat exchanger are sound.

Do I even need the furnace in Florida?

More than new arrivals expect. January in Zephyrhills averages a low around 47 degrees, and there are colder nights than that most winters. An RV holds almost no heat. Winter residents who arrive in November, run nothing but the AC for a month, and never test the furnace find out about it on the first cold night, which is why a test run on arrival is worth doing.

Why does my furnace run constantly and never reach the setpoint?

Usually duct losses, an undersized furnace for the rig, or a thermostat placed where it reads the wrong temperature. Sometimes it is a partly blocked return. In a poorly insulated rig on a 40-degree night, a furnace running most of the time can be normal.