By Derim “Mike” Vinca, Owner of A-1 Milwaukee Heating & Cooling · 17+ years in the trade · Updated October 2026 · More HVAC guides
We would rather you fix a tripped switch yourself than pay us to flip it. A surprising share of the no-heat calls we get turn out to be one of the six items below, so go through them in order. If the furnace is still dead at the end, call or text 414-595-5175 and we can usually be there the same day.
If you smell gas, leave the house and call We Energies at 800-261-5325 or 911 before you call anyone else. If a carbon monoxide alarm is sounding, get everyone outside and call 911.
1. Thermostat
Make sure it is set to Heat, not Off or Cool, and the setpoint is at least 5 degrees above room temperature. If the screen is blank, replace the batteries. Smart thermostats sometimes lose their schedule after a power blip; set a manual temperature and see if the furnace responds within a few minutes.
2. The furnace power switch
There is a light-switch-style toggle on or next to the furnace. It looks exactly like a light switch, and in Milwaukee basements it gets bumped off by laundry baskets, kids and contractors all the time. Make sure it is on.
3. The breaker
Find the furnace breaker in your panel. If it is tripped, push it fully off and then back on. If it trips again, stop and call us; something is shorting.
4. The filter
A filter that is packed solid overheats the furnace and trips the high-limit switch, which shuts the burners off. Pull the filter. If you cannot see light through it, replace it. Then turn the power switch off for 30 seconds and back on to reset the control board.
5. The blower door
The lower panel on the furnace presses a safety switch. If the panel is not fully seated, the furnace will not run at all. Push it firmly in until it clicks.
6. Condensate (high-efficiency furnaces)
If your furnace vents through white PVC pipe, it produces water. If the drain line or condensate pump is clogged or frozen, a float switch shuts the furnace down. Look for standing water in the trap or pump reservoir, and check that the outdoor PVC intake and exhaust are not blocked by snow or ice.
Still nothing? Here is what it probably is
If the furnace tries to start and fails, it is most often a dirty flame sensor, a cracked hot-surface ignitor, a failed inducer motor or a pressure switch problem. If it does absolutely nothing, it is usually the control board, the transformer or a door switch. Most of these are same-day repairs with parts we carry on the truck. Many furnaces also flash a diagnostic code through a small window on the front; count the blinks and tell us when you call. It saves time.
What to expect when you call A-1
Calls ring Mike’s cell at any hour, and you get a real arrival window. On site we test, show you the readings and quote a flat-rate price before touching anything. If the furnace is unsafe or at the end of its life we tell you plainly and explain why; if a part fixes it, that is what we recommend. More on our furnace repair and 24/7 emergency service. We are based in South Milwaukee and work throughout Milwaukee and Waukesha counties. Call or text 414-595-5175.
Frequently asked questions
My furnace clicks but never lights. What is that?
Usually a failed hot-surface ignitor or a flame sensor that is too dirty to prove flame. Both are quick repairs.
The blower runs but the air is cold. Why?
The burners are not lighting or are shutting down early. Check the filter and the thermostat first; if those are fine, it needs a diagnostic.
Is a no-heat call an emergency?
In a Milwaukee winter, yes. Pipes can freeze within a day when it is below 20 degrees. Our emergency line is answered 24/7, nights, weekends and holidays included.