Oklahoma has a way of skipping fall. One week you're running the A/C, and the next you wake up to a cold camper and a furnace that hums, clicks and gives you nothing but cold air. If that's where you are right now, you're not alone. The first cold snap is when most RV furnaces show the problems they've been hiding all summer.
The good news is that a lot of furnace trouble comes down to a short list of causes. Some of them you can check yourself in a few minutes. Others need someone who works on these systems every day. Here's how to tell the difference.
How an RV furnace lights, in plain terms
Most RV furnaces run on two things at once: propane for the heat and 12-volt power for the fan and the controls. When you turn up the thermostat, the fan starts first. Once it's moving enough air, a small switch inside (often called a sail switch) closes and tells the control board it's safe to light. The board opens the gas valve and makes a spark. If the board senses a flame, the furnace keeps running. If it doesn't, it tries a few times and then locks out.
That chain is why a furnace can fail in so many ways. A problem with the propane, the 12-volt power, the airflow or the controls can all end in the same cold air.
Common reasons an RV furnace won't light
Low or empty propane. It sounds too simple, but it's one of the most common. Gauges on propane tanks aren't always accurate, and in cold weather a nearly empty tank may not push enough gas. If your stove burners are weak or won't light either, start there.
A closed valve. If the RV was stored or just had a tank swapped, a valve may still be closed. Check the tank valve and make sure any shutoff inside the coach is open.
Low 12-volt battery voltage. This one fools a lot of owners. The furnace fan needs good 12-volt power. If your battery is low, the fan may spin, but too slowly to close the sail switch, so the furnace never even tries to light. Cold weather makes weak batteries weaker.
Blocked airflow. Furniture, blankets or storage bins pushed against the return-air vent can starve the furnace of air. Blocked ducts or closed registers can cause it to shut off on its high-limit safety.
Nests and debris. RVs that sat all summer are a favorite spot for insects and small critters. A nest in the burner tube or the outside exhaust can stop the flame or cause it to light poorly.
Worn or failed parts. Sail switches, limit switches, igniters, gas valves and control boards all wear out over time. These need proper testing, not guesswork.
What you can safely check yourself
Before you call, walk through this short list:
- 1Make sure the thermostat is set to heat and turned a few degrees above room temperature.
- 2Confirm you have propane. Light a stove burner to see if gas is flowing.
- 3Check that the propane tank valve is fully open.
- 4Check your battery. If you're plugged into shore power, make sure the converter is charging. If you're not plugged in, a low battery is a strong suspect.
- 5Clear anything blocking the return-air vent and the floor registers.
- 6Look at the outside furnace vent for anything obvious blocking it.
- 7Turn the furnace off, wait a few minutes, and try once more. Many furnaces lock out after a few failed tries.
If it still won't light, stop there. Cycling it over and over doesn't fix the problem and can make it harder to diagnose.
Safety first
- If you smell propane, turn off the gas at the tank, don't flip switches or light anything, open the door, and get out of the coach. Don't use the furnace until it's checked.
- Make sure your carbon monoxide detector and propane detector work. They have expiration dates, and an old detector may not warn you.
- Never use the stove or oven to heat the RV. They aren't vented for it.
- Space heaters can help in a pinch on shore power, but use them carefully, keep them away from bedding and curtains, and don't overload your circuits.
Furnace symptoms and what they usually point to
| What you notice | Common areas to check |
|---|---|
| Fan runs, never lights | Low battery, sail switch, propane supply, board |
| Lights, then shuts off | Airflow, limit switch, flame sensing, gas pressure |
| Clicks but no fan | Power, thermostat, fan motor, board |
| Nothing at all | Fuse, thermostat, wiring, 12-volt power |
| Burning smell on first use | Dust burning off (normal briefly); call if it lasts |
When to call for repair
Call when the simple checks don't fix it, when the furnace lights but won't stay lit, when you smell gas, or when you hear grinding or squealing from the fan. Those are signs of a part that needs to be tested and replaced, not adjusted.
When Frederick looks at a furnace, he checks it in order: power, propane, airflow, then the parts in the lighting sequence. That way you're not paying for a new control board when the real problem was a weak battery. You get the diagnosis, the options and the price before any work starts. Parts are billed at what they cost, with no markup.
Before you head out this winter
If your furnace worked fine, it's still worth running it for a full cycle before your first cold trip. A furnace that struggles on a mild day will usually quit on the coldest night. Running it at home, with your detectors tested and your battery charged, means you find the problem in your driveway, not at a campsite.
Furnace not cooperating? Call Frederick at (405) 429-9795 or send a request. First-time customers get 25% off the entire job.
Questions
Quick answers
Usually the fan is running but the burner isn't lighting. Low battery voltage, a propane supply problem or a failed part in the lighting sequence are the most common causes.
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