Problem: Furnace Starts Then Shuts Off Quickly

Why Does My Furnace Start Then Shut Off Quickly?

If your RV furnace starts normally but shuts off after only a few seconds or minutes, the problem is usually related to flame sensing, airflow, or overheating protection.

In many cases, the furnace actually ignites successfully — but one of the safety systems immediately shuts the burner back down.

This is a very common issue in both Suburban and Dometic (Atwood) RV furnaces.

The Most Common Cause: Dirty or Weak Igniter Electrode

In most RV furnaces, the igniter electrode performs two jobs:

  • Creates the spark to light the burner
  • Confirms the flame is present

If the furnace lights but shuts off quickly, the control board may not be detecting the flame properly.

Common Symptoms

  • Furnace ignites briefly then shuts down
  • Heat starts for a few seconds before turning cold
  • Furnace retries ignition repeatedly
  • Clicking or cycling noises during startup

Why the Electrode Stops Working Properly

Over time, the electrode can develop:

  • Carbon buildup
  • Corrosion
  • Cracks in the ceramic insulation
  • Improper spark gap or alignment

Even if the burner lights, the furnace may still shut down if the flame signal is weak.

The Next Most Likely Cause: Overheating Limit Switch

If the furnace overheats, the limit switch shuts the burner down while the blower fan may continue running.

Common Causes

  • Restricted airflow
  • Dirty ducts or vents
  • Weak blower motor
  • Blocked furnace exhaust

Symptoms

  • Furnace runs for a minute or two, then shuts off
  • Blower may continue running
  • Furnace restarts later and repeats the cycle

Less Common Causes

Weak Propane Flow

Low gas pressure can cause unstable flame operation.

Check:

  • Propane level
  • Regulator performance
  • Kinked or restricted lines

Failing Control Board

If the board cannot properly read the flame signal, it may shut the furnace down even when ignition is successful.

This is less common than electrode or airflow issues, but still possible.

Recommended Repair Order

For the fastest and most affordable fix:

  1. Clean the igniter electrode
  2. Check electrode alignment
  3. Replace the electrode assembly
  4. Inspect airflow and limit switch
  5. Move to control board diagnosis if needed

Pro Tip

If your furnace is older and you’re already opening it up, many RV owners replace both:

  • Igniter electrode
  • Limit switch

These are common wear items and relatively inexpensive compared to repeated troubleshooting.