How To Avoid An Expensive Service Call When Your Gas Heater’s Pilot Light Won’t Stay Lit

In nearly 30 years working in propane gas sales and service, the most frequent service calls that I receive are pilot light outages. Most of these calls take less than 5 minutes to fix, but cost the customer $30 to $50 depending on driving time. The only tools that I have to take in are a screwdriver, flashlight, and a can of electronics duster.

First, it helps to have a basic understanding of how the pilot works. The gas flows through a tiny orifice into the pilot tube. Due to something known as the venturi effect, air is pulled into the tube through holes in its side. This air is mixed with the gas in the tube to produce a mixture for optimal combustion, characterized by a strong blue flame.

This flame strikes a thermocouple mounted in front of the pilot tube. When the thermocouple is heated, it produces a tiny electric current. This current operates the gas valve.

If a small amount of dust is sucked into the pilot tube, it can disrupt the mixing of the air and gas. This may cause the pilot to exhibit a bright yellow tip or to be reduced in size and intensity. This flame will not heat the thermocouple sufficiently, causing the valve to shut off the gas flow, and the pilot to go out.

The system is designed this way to act as a safety. When the thermocouple cools, the heater ‘thinks’ the pilot has gone out, and cuts off all gas going through the valve. This would prevent the possibility of an explosion if it was really out.

In most cases, the dust can be simply blown out of the tube with a can of electronics duster (like you use to dust your keyboard). Just slide the straw to the bottom of the pilot tube, pull it back a bit, and pull the trigger. Slide the straw up and out as you blow.

Fan the spray and allow it to dissipate for a few minutes before relighting the heater, as these dusters will burn. Most also have a bittering agent added to prevent abuse. This produces a very unpleasant smell when it burns.

Understanding how various gas appliances operate can save you hundreds of dollars in unnecessary service calls. The most common calls generally involve cleaning some part of the appliance that could have been done by the homeowner with a little know – how.