RV Water Heater Pilot Light Won't Stay Lit: Thermocouple Troubleshooting Guide

Tools & Parts Needed

Find these on Amazon: Universal RV Water Heater Thermocouple , Wire Brush Set for Cleaning , Digital Multimeter

What's Going On

Here's what you're dealing with. Your RV water heater pilot light won't stay lit because the thermocouple isn't detecting the flame properly. This safety device shuts off gas flow when it doesn't sense heat from the pilot flame. The fix usually involves cleaning or replacing the thermocouple, which costs $15-30 and takes about 30 minutes.

Why This Happens

Dirty or corroded thermocouple: Over time, the thermocouple tip accumulates soot and corrosion that insulates it from the pilot flame heat. Regular cleaning prevents this issue.

Thermocouple positioned incorrectly: If the thermocouple tip isn't in the pilot flame's path, it won't heat up properly. The flame should wrap around the tip when burning correctly.

Weak or dirty pilot flame: A yellow or weak pilot flame indicates a dirty orifice or insufficient gas pressure. The flame should be blue and steady, about 1/2 inch high.

Faulty gas control valve: Less commonly, the gas control valve itself may be malfunctioning and not responding properly to the thermocouple signal.

Loose connections: Check that all connections between the thermocouple and gas valve are tight and secure.

Getting Ready

Before diving in, gather these items:

• Replacement thermocouple (if needed)
• Adjustable wrench or pliers
• Wire brush or steel wool
• Compressed air or soft brush
• Multimeter (for testing)
• Flashlight or headlamp

Walking Through the Fix

Here's how to tackle this:

1. Turn off the gas supply at the water heater and allow the unit to cool completely before starting any work.
2. Remove the access panel to expose the pilot light assembly and locate the thermocouple - a thin metal rod positioned near the pilot flame.
3. Clean the thermocouple by gently scrubbing the tip with fine steel wool or wire brush to remove any corrosion, soot, or debris that could prevent proper heat detection.
4. Check the thermocouple position - it should be positioned so the pilot flame wraps around the tip. Gently bend it closer if it's too far from the flame path.
5. Clean the pilot orifice using compressed air or a soft brush to remove any spider webs, dirt, or debris that could affect flame quality.
6. Test the thermocouple with a multimeter set to millivolts - it should read 25-30 millivolts when heated by the pilot flame. Readings below 20 millivolts indicate replacement is needed.
7. Replace the thermocouple if cleaning doesn't solve the problem by unscrewing it from the gas control valve and pilot assembly, then installing the new one in reverse order.
8. Relight the pilot following your water heater's lighting instructions, ensuring you hold the button long enough for the new thermocouple to heat up (usually 30-60 seconds).

Beyond DIY Territory

Contact a certified RV technician if you encounter any of these situations:

• You smell gas after completing repairs
• The gas control valve appears damaged or won't operate properly
• You're uncomfortable working with propane appliances
• The problem persists after replacing the thermocouple
• You need to remove or adjust gas lines