Intermittent Water Heater Operation

Welcome to another Tech Tip Tuesday from the National RV Training Academy! Today, Todd dives into troubleshooting a Dometic water heater with a unique issue: it starts up fine, but the flame intermittently goes out, causing the system to shut down and attempt re-ignition.

This common problem for RV owners is brought to us by Lori, who’s seeing her water heater start but then kick off randomly. Lori’s question touches on propane water heaters that start well but fail to stay lit, sometimes lasting just 30 seconds before shutting off. Todd breaks down some possible causes and fixes, from faulty wiring to the need for proper cleaning.

The Problem: Intermittent Flame and Shutdown

Lori’s Dometic water heater works fine for a few moments, but then the flame goes out, the system shuts down, and sometimes the reset light (or “no flame” light) comes on. If this happens, she has to turn the water heater off and back on to reset it, which indicates it’s cycling through multiple attempts to ignite before finally giving up. Todd explains that if the system tries to ignite three times but doesn’t sense a flame, it will turn off and trigger the reset light.

Diagnosing the Cause: Check for Obstructions and Damaged Wires

After Lori inspected her heater, she found some charring on the red wire connecting to the ECO (emergency cut-off) fuse. Todd explains that if flames are shooting near the burner area, the wires may be burned or damaged, causing intermittent functionality. Charred wires signal excessive heat buildup or an obstruction in the burner, leading to incomplete combustion.

Here’s what could be happening:

1. Obstruction in the Burner Tube: If debris or soot is blocking the burner, it disrupts airflow and can cause flames to leak out of the burner area, causing heat to accumulate around the wiring.
2. Low-Hanging Wires: In some Dometic models, wires around the burner area can hang too low, making them more vulnerable to heat damage.

Fixing the Problem: Steps for Safe and Effective Repair

1. Inspect for Soot or Blockages: Soot around the burner area indicates a blockage that prevents proper airflow, leading to excess heat and carbon buildup. Todd suggests using an endoscope or a boroscope to inspect the inside of the burner tube.
2. Clear the Burner Tube: If there’s an obstruction, try using an old hanger to gently clean out the tube. The burner tube has a looped design, so a straightened hanger can work to clear minor obstructions.
3. Replace Damaged Wires: Charring is a sign that the wire needs replacement. Burned wiring will have compromised functionality and may cause more shutdowns. Replacing it is essential for safety and reliable performance.

Driving with the Water Heater On: A Possible Cause of Flame Issues

Running your water heater on propane while driving can create another issue. When you’re driving at high speeds, the low-pressure environment outside the vehicle can pull the flame out of the burner, increasing the risk of charring or flame-out issues. Todd recommends turning off your propane appliances, especially the water heater, while driving to avoid this.

Final Tips: Prevention and Maintenance

• Inspect Annually: Regularly inspect your water heater for signs of wear, such as soot, charring, or frayed wires.
• Clear Debris: Clean the burner tube periodically to prevent obstructions from accumulating.
• Switch Off While Driving: Avoid running your propane appliances, especially ones with open flames, while on the road.

By following these tips, you can keep your RV water heater in excellent condition and avoid frustrating shutdowns. For further assistance or questions, reach out to the National RV Training Academy. And as always, don’t forget to like and subscribe for weekly RV tech tips to keep your adventures safe and enjoyable!