By Johnathan Mason, Ace Chimney Service.
The first cold evening, the switch goes on, and nothing happens. It is one of the most common calls of the season, and the cause is usually one of a handful of things at the pilot assembly. Here is what is going on, and where the line is between what you can check and what needs a technician. Relevant to plenty of Lakewood homes with gas logs or sealed units.
How a standing pilot system works
Most older gas fireplaces are millivolt systems, and the clever part is that they generate their own electricity. The pilot flame heats a device called a thermopile, which produces a small voltage — enough to hold the gas valve open and let the wall switch or remote operate the fireplace. No household power required, which is why these units keep working in an outage. It also means that if the thermopile weakens, the whole thing stops responding.
The usual suspects
A pilot that will not stay lit after you release the knob usually points to a weak or failing thermocouple or thermopile, or a pilot flame that is not properly enveloping it. A pilot that lights and holds but a fireplace that ignores the switch points to a thermopile producing voltage but not enough, a failed switch, or wiring. A pilot that will not light at all can be a plugged pilot orifice, a closed shutoff, or an air-in-the-line issue after service.
Dust is the quiet villain
Over a summer, a gas fireplace collects dust, lint, pet hair, and spider webs. Spiders in particular are drawn to gas pilot assemblies, and a web in the pilot orifice will produce a lazy yellow flame that no longer heats the thermopile properly. A good portion of first-cold-night failures are cleaning problems, not part failures. That is exactly what an annual gas fireplace service visit addresses.
What you can safely do
Confirm the gas valve is on and any wall switch is in the on position. Check that a remote’s batteries and the receiver’s batteries are good, since dead batteries mimic a dead fireplace. Follow the lighting instructions printed on the unit exactly. That is the sensible limit. Do not disassemble the valve, do not adjust the pilot yourself, and if you smell gas at any point, leave the house and call the gas utility from outside.
The venting still matters
Gas produces no creosote, which leads people to assume gas fireplaces need nothing. The vent still needs to be clear, intact, and correctly terminated, and a blocked vent on a gas appliance is a carbon monoxide problem. Annual service and an inspection apply to gas as much as to wood.
Ace Chimney Service has 29 years in fireplace work, is insured and bonded, quotes the price up front, and covers Crystal Lake and McHenry County seven days a week from 7 AM to 7 PM. Call (815) 320-0883.
Frequently asked questions
Why will my pilot not stay lit?
Most often a failing thermocouple or thermopile, or a dirty pilot orifice producing a flame that no longer heats the sensor properly.
What is a thermopile?
A device heated by the pilot flame that generates the small voltage holding the gas valve open. It is why millivolt fireplaces work without house power.
The pilot is lit but the switch does nothing — why?
Usually a weak thermopile, a failed wall switch, or a wiring or remote-receiver fault.
Can spiders really stop a gas fireplace?
Yes. Webs in the pilot orifice are a well-known cause of weak pilot flames and are cleared during annual service.
Should the pilot stay on all summer?
Many owners shut it off to save gas and reduce heat. Either is acceptable; follow the manufacturer’s guidance for your unit.
Do gas fireplaces need the chimney swept?
Not for creosote, but the vent must be inspected for blockage, corrosion, and correct termination.
Why does my gas fireplace smell when first used?
Dust burning off the logs and burner. It should clear within a short time; a persistent gas smell is an emergency.
Do I need a carbon monoxide alarm with a gas fireplace?
Yes, and it should be tested at the start of every heating season.
Published September 14, 2026