Preparing Your Furnace for the First High Desert Cold Snap

The right time to schedule a furnace tune-up is September or early October, before the first cold front arrives. We start running heating tune-up calls in mid-September and the schedule fills up through October. By the first week of November, when the first 28F night usually hits, same-day no-heat calls jump and routine tune-up appointments push out two to three weeks. There are three reasons fall tune-up matters more than spring tune-up. First, the system has been sitting unused for five to six months. Dust accumulates in the burner compartment, mice and bird nests show up in flue pipes, and condensate from summer humidity (yes, even High Desert summers produce some) can corrode metal components. Second, the failure modes that produce carbon monoxide (cracked heat exchanger, blocked flue, failed flame sensor) are not visible from the outside and require a professional inspection. Third, gas pressure and combustion analysis on a working furnace can only be done with the system actually running, and it is much better to find a problem in 70F October weather with the heat off than at 11pm on a 22F night with the family in the house. Tune-up runs $99-$149 standalone or is included annually with the Service Agreement.

Most Hesperia, Apple Valley, and Victorville valley homes are on natural gas through SoCalGas, with parts of Apple Valley served by Liberty Utilities. Phelan, Pinon Hills, Wrightwood, Oak Hills, and Lucerne Valley homes are predominantly on propane, either underground tanks or above-ground tanks fed by a local supplier (AmeriGas, Suburban, Ferrellgas). Propane behaves differently than natural gas in cold weather. Propane is stored as a liquid under pressure in the tank, and it has to vaporize to flow to the furnace. Vapor pressure drops as outdoor temperature drops. Below about 20F ambient, propane vapor pressure starts to fall measurably, and a tank that is below 30 percent full may not be able to deliver enough vapor to fire the furnace at full demand on the coldest nights. The fix is two-part. Keep propane tanks above 30 percent full through the winter, and call the supplier in early November to schedule a refill before peak demand. Natural gas pressure is regulated at the meter and stays consistent, but a partially blocked or rusted gas line at the appliance can drop pressure at the burner and cause ignition failures. Combustion analysis during a tune-up measures both gas pressure and the resulting flame characteristics, which is the only reliable way to verify the burner is getting what it needs.

Modern furnaces use a hot-surface ignitor (a thin silicon nitride or silicon carbide element that glows red when energized) to light the burner. Ignitors are consumable parts that fail on a roughly 5-7 year cycle, and they fail more often on cold-start in November because the ignitor is being asked to work after a long idle period. Symptoms of a failing ignitor include the furnace clicking through its startup sequence (inducer fan starts, then nothing) without the burner lighting. Replacement is straightforward, $150-$250 in parts and labor, and we carry common ignitor types on every truck. The pressure switch is a small safety component that confirms the inducer fan is producing the correct draft before the gas valve opens. A blocked flue, a flue obstruction (bird nest is the most common, especially after summer), or a failing inducer fan all cause the pressure switch to keep the gas valve closed. Both the ignitor and the pressure switch get tested during a fall tune-up under actual operating conditions. Catching a marginal ignitor or a borderline pressure switch in October prevents the 11pm no-heat call when it finally fails on the coldest night.

If the furnace fails during a hard freeze, work through the safe checks first before calling for service. Look at the thermostat, confirm it is set to heat and the temperature setting is above current room temperature. Check the breaker panel for a tripped breaker on the furnace circuit (some furnaces have two breakers, one for the system and one for the blower). Check the filter, a fully clogged filter can trip a high-limit safety. Look at the gas supply, if the range and water heater also are not working, the issue is at the meter or the supplier, not the furnace. For propane homes, check the tank gauge, anything under 20 percent in cold weather is a problem regardless of furnace condition. Once safe checks are done, call us. Same-day dispatch is faster in winter than summer because winter peak demand is shorter and less geographically synchronized. While waiting, set up safe alternative heat. Plug-in electric space heaters work for one or two rooms. Never use a gas oven, charcoal grill, or unvented gas heater to warm a house, all three produce CO. Close off unused rooms to concentrate heat where the family is. If the home gets below 50F overnight, drip cold-water faucets to prevent pipe freeze, especially in homes with exterior-wall plumbing or higher elevations like Phelan and Wrightwood.