Why Is My Furnace Not Heating? A Michigan Troubleshooting Guide
The most common reasons a furnace will not heat are a thermostat setting, a clogged filter, a tripped breaker or switch, a pilot or igniter problem, or a safety limit shutting the burner down. Check the simple things first, and if the furnace still will not heat, call for service before the house gets cold.
When the heat quits in a Michigan winter, a few quick checks can sometimes save you a service call, and knowing the signs helps you describe the problem when you do call. This guide covers what you can safely check yourself and what needs a licensed technician.
One rule first: if you ever smell gas or a carbon monoxide alarm sounds, leave the house and call for help. Everything else below is safe to check.
Start with the simple things
Before you call anyone, confirm the thermostat is set to heat and a few degrees above room temperature, check that the furnace filter is not clogged (a dirty filter is one of the most common causes of furnace problems), make sure the furnace power switch is on and the breaker has not tripped, and check that supply vents are open. These free checks solve a surprising number of no-heat calls.
- Thermostat set to heat, above room temperature, with fresh batteries
- A clean furnace filter, replace it if it is gray and clogged
- Furnace power switch on and breaker not tripped
- Supply and return vents open and unblocked
| You can safely check | Call a technician for |
|---|---|
| Thermostat set to heat | No ignition or repeated lockouts |
| Furnace filter (replace if dirty) | Cracked heat exchanger / CO alarm |
| Breaker and furnace switch | Gas valve or control board faults |
| Vents open and unblocked | Blower motor failure |
| Batteries in the thermostat | Anything involving the gas line |
What needs a licensed technician
If the simple checks do not restore heat, the cause is usually inside the furnace: a failed igniter or flame sensor, a bad blower motor, a gas valve or control board fault, or a safety limit shutting things down. These need a licensed technician with the tools to diagnose safely. Guessing at gas appliance parts is not worth the risk.
| Symptom | Likely cause |
|---|---|
| Blowing cold air | Thermostat on fan, clogged filter, or failed igniter |
| No air at all | Breaker, switch, or blower motor |
| Short cycling | Dirty filter, overheating limit, or oversized furnace |
| Clicks but no ignition | Igniter, flame sensor, or gas supply |
| Burner lights then quits | Dirty flame sensor or limit switch |
If you smell gas, or a carbon monoxide detector goes off, leave the house and call from outside. Do not try to diagnose a gas leak or a suspected cracked heat exchanger yourself. Then call Oak Grove.
When to just call the OG
If it is bitterly cold, the house is dropping, or you have checked the basics and still have no heat, do not wait. Oak Grove handles emergency calls across Livingston and Oakland counties. Call (517) 618-7100 and we will get your heat back.
Why Is My Furnace Not Heating? A Michigan Troubleshooting Guide FAQ
Why is my furnace blowing cold air?
Common causes are the thermostat set to fan instead of auto, a clogged filter, a failed igniter or flame sensor, or a safety limit shutting the burner down. Check the thermostat and filter first, then call if it persists.
Why does my furnace keep shutting off?
Short cycling is often a clogged filter, an overheating limit switch, a dirty flame sensor, or an oversized furnace. We diagnose the exact cause rather than guessing at parts.
What should I check before calling for furnace repair?
Confirm the thermostat is set to heat and above room temperature, replace a dirty filter, check the furnace switch and breaker, and make sure vents are open. If it still will not heat, call for service.
Is it safe to keep restarting my furnace?
If it locks out repeatedly, stop and call, because it is shutting down for a reason. And if you smell gas or a CO alarm sounds, leave and call from outside immediately.