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RV Furnace or Water Heater Not Working? Start Here

Disclosure: Some links on this site may be affiliate links; see our disclosure. Safety first: if you smell propane, shut off the LP tank, don't operate switches, get everyone out, and call for service. Always use your carbon monoxide and LP detectors, and test them before each trip.

A cold morning in the mountains is when the furnace quits, and a long weekend is when the water heater won't light. Most failures come from a few simple causes you can check at the campsite.

Part 1: RV furnace

Symptom: Fan runs but no heat (or it blows cold, then shuts down)

Most RV furnaces run the blower first and only light the burner after a sail switch confirms enough airflow. If airflow is weak, the burner won't light.

  1. Check 12-volt battery voltage. This is the most common cause. A weak battery spins the blower too slowly to close the sail switch. Measure at the battery with the furnace running. If it's low, plug in or run the generator to charge and try again. (The Suburban water heater service manual specifies a DC operating range of 10.5–13.5 V for that unit, which gives you an idea of how sensitive these appliances are to voltage; check your furnace manual for its own range: Suburban Master Service Manual.)
  2. Check the return-air grille and ducts. Blankets, a shoe, or a crushed duct can starve airflow.
  3. Is there propane? Light a stove burner. If the stove's weak or dead, check the tank and regulator.
  4. Air in the lines after a tank swap: Run a stove burner for a minute to purge, then try the furnace again. Most furnaces try to light a few times and then lock out. Turn the thermostat off for a minute to reset.

Symptom: Clicking, but never lights

Clicking is the igniter trying. Check propane supply first. After that, a dirty or misaligned electrode or a bad control board needs a tech, because burner and gas-valve work involves the gas train.

Symptom: Nothing at all

Outside exhaust vent

Check for wasp nests or debris in the exterior exhaust and intake. Never block it, and never use the kitchen stove or oven to heat the rig. That's a carbon monoxide risk.

Part 2: RV water heater

The #1 rule: fill it before you power it

Suburban's service manual tells technicians to confirm the tank is full of water before energizing the electric element (Suburban Master Service Manual). Turning on the electric switch with an empty tank (after winterizing, or with the bypass valve still set to bypass) can burn out the element in moments. Open a hot faucet until water, not air, comes out.

Symptom: Not heating on electric (works on gas)

  1. Bypass valves: After winterizing, the water heater is often bypassed. Set the valves back to normal and fill the tank.
  2. Electric switch: It's often a separate switch from the gas switch, sometimes on the outside of the unit.
  3. 120-volt power: Check the breaker and confirm shore power or the generator is on.
  4. Reset button / thermal cutoff: Many units have a high-limit reset on the electric thermostat. Find it in your manual.
  5. Element: If all of the above is fine, the element may have failed. It's a common part, but you must drain the tank before replacing it.

Symptom: Not igniting / won't stay lit on gas

  1. Propane present? Test with the stove.
  2. Air in the line after a refill. Try a few times.
  3. Debris in the burner tube: Spiders love the tube; their webs block gas flow and cause weak, yellow or no flame. Cleaning the burner tube is a classic fix, but only if you're comfortable working on gas appliances. Otherwise call a tech.
  4. DC voltage: The igniter board needs proper 12-volt power. Check the battery.
  5. Flame lights, then goes out: This often points to a sensor or control issue. The Suburban manual covers testing the reigniter and gas valve; that's tech territory for most owners.

Symptom: Water lukewarm, not hot

Anode rod (Suburban-type steel tanks)

Many Suburban water heaters use a sacrificial anode rod to protect the tank, and it wears away over time. Inspect it when you drain the tank. Atwood/Dometic aluminum tanks generally don't use one; check your model.

Tools worth carrying

When to call a pro

Any gas smell, a burner that won't light after the basic checks, control board diagnosis, or anything you're not comfortable doing. A mobile RV tech can often come to your campsite; ask the campground office.

FAQ

Why does my RV furnace blow cold air? The most common reason is low 12-volt battery voltage. The blower turns too slowly to close the sail switch, so the burner never lights.

Why is my RV furnace clicking but not igniting? The igniter is sparking, but there's no gas or the flame isn't being sensed. Check propane first. After that, it's usually a job for a technician.

Why does my RV water heater work on gas but not electric? Check the electric switch, breaker, reset button and bypass valve. The element may have burned out, especially if it was ever turned on with an empty tank.

Can I turn on the water heater with no water in it? No. Suburban's manual says to make sure the tank is full before energizing the electric element. Dry-firing can destroy the element.

Is it safe to sleep with the RV furnace on? RV furnaces are vented outside and designed for overnight use, but only with working, tested carbon monoxide and LP detectors and clear exterior vents. Follow your manual.

Sourced from manufacturer service documentation linked above. Last checked 2026-10-21.