The first real cold snap of the fall is when a lot of Western Montana furnaces show their problems. A furnace that sat all summer gets switched on, and it doesn't start, it blows cold air, or it runs for a minute and shuts off. Before you panic, a few simple checks can save you a service call, and they'll also help you tell us what's going on if you do need us.
First, safety
If you smell gas (rotten eggs) or propane, don't troubleshoot. Don't flip switches, and don't light anything. Get everyone out of the house and call your gas utility or propane supplier, or 911, from outside. If a carbon monoxide alarm is going off, get out and call 911. Everything below is only for a furnace that just won't heat, with no smell and no alarm.
1. Check the thermostat
It sounds obvious, but this is where most fall "no heat" calls start. Make sure it's set to Heat, not Cool or Off, and set a few degrees above the room temperature. If the screen is blank, replace the batteries. On a smart thermostat, check that a schedule or eco mode isn't holding the temperature down.
2. Check the power
Most furnaces have a switch that looks like a light switch on or near the unit, and it's easy to bump off during summer storage or cleaning. Make sure it's on. Then check your electrical panel for a tripped breaker. With an electric furnace, look for a tripped breaker especially carefully, since those units draw a lot of power. If a breaker trips again right after you reset it, stop there and call us.
3. Look at the filter
A badly clogged filter can make a furnace overheat and shut itself off, sometimes after only a few minutes of running. If you can't see light through yours, replace it. Fall is a good time to start with a fresh filter anyway.
4. Make sure the door panel is closed
Furnaces have a safety switch that keeps the unit from running when the front panel isn't seated right. If someone changed the filter or looked inside, make sure the panel is fully pushed into place.
5. Check your fuel
On a propane furnace, check the gauge on your tank. Running low or out is a common reason a propane furnace won't light, and after a refill the system may need to be checked and relit safely. On a natural gas furnace, make sure the gas valve to the furnace is in the on position, with the handle in line with the pipe. If other gas appliances in the house are working, gas supply probably isn't the issue.
6. Check the vents and outside pipes
High-efficiency furnaces vent through plastic pipes on an outside wall or the roof. Snow, ice, leaves, or a wasp nest can block those pipes and keep the furnace from running. Make sure they're clear, and keep them clear all winter. Inside, make sure supply vents and return grilles aren't covered by furniture or rugs.
7. Watch the blinking light
Many furnaces have a small window with a status light that blinks a code. You don't need to decode it yourself, but counting the blinks and taking a photo of the code chart on the panel door helps us show up ready.
When to call a pro
Call us if you've done these checks and the furnace still won't heat, if it keeps turning on and off, if a breaker keeps tripping, or if you hear banging, screeching, or grinding. Igniters, flame sensors, pressure switches, blower motors, and control boards all fail, and in a Montana winter you don't want to guess. ProCare Climate repairs gas, propane, and electric furnaces of every brand, and you can learn more on our furnace repair page.
Help across Western Montana, 24/7
ProCare Climate is based in Missoula, and Jeremy has more than 10 years of hands-on HVAC experience in Western Montana. We serve homes and businesses in Missoula, Lolo, Frenchtown, Stevensville, Hamilton, Polson, and the surrounding area, and we answer the phone 24/7, because furnaces don't only quit during business hours.
If your furnace won't start, give us a call at 406-546-1289. And if your old furnace is showing its age, request a free install estimate right here on the site.