Chicago Heating and Furnace Components Part 1 | Furnace Repair Tips

This is going to be the first part in a two-part article that will describe the main components of a furnace and some tips to resolve problems that can be associated with the furnace. In this part one article I will be speaking about furnaces that are made within the past 15 years, give or take. The type of furnace problems will be associated with furnaces that have draft induction rather than older furnaces with natural draft. Some of the components are the same on both, yet this type of draft induction system furnace is more complex and complicated.

The following is for informational use only and is not intended as a “How to Guide”.  Gremillion Mechanical always recommends that if there is a problem with any complex appliance in your home to call a professional service technician trained in the repair of that equipment.  Remember to always “stay in your comfort zone” when trying to perform any task related to your furnace and if you feel unsafe, call for professional help!

The main components of a furnace that I will be speaking about are: inducer motor, pressure switches, limits, main gas valve, circuit board, blower motor, and main burners. Some of these components like the limits, main gas valve, blower motor, and main burners will be the same on most furnaces so some of the tips in this article will be relevant in most units.

One of the first things that needs to be checked to see why your furnace is not operating properly is power. You need to check to make sure you have both low voltage and high voltage to the unit. A very easy way to check this is by turning your fan to the on position on the thermostat. If the fan comes on then you know that you have the low voltage to the thermostat and the high voltage to the furnace. If the fan does not turn on you can check the batteries in the thermostat and the circuit breaker labeled furnace in the breaker panel. If you still have no power to the unit and you do not have a meter to check for power you need to contact a heating and air conditioning professional to diagnose.

Next, if you have power and the fan in the furnace is blowing you need to set the thermostat fan to auto and turn the thermostat to heat. Go to the furnace and look in the top door and see if the inducer fan in the upper cabinet is spinning. If it is possible to take the door, do so to get a better look at the components. If the inducer motor is not spinning see if you can spin the black wheel in it by hand to see if it spins freely. If it seems hard to spin and the motor itself seems hot the motor can be in question. If you have a multi meter you can check if you have 120 volts to the motor and it is not working that is the problem.

If the motor is not spinning try to look in the bottom compartment through a little looking-glass hole and locate the circuit board. On this board you should be able to see a little red flashing light. If you can locate the red flashing light determine the number of times and the sequence that it flashes. This will correspond to a code that you can normally find on the inside of the bottom furnace door that will help to diagnose the problem much faster. If no code you need to determine why the motor is not spinning which might be a job for a professional heating and cooling contractor.

If the motor is spinning the next thing that should be seen is some sort of igniter that will light the gases from the gas valve to the burners. Most newer models will have an igniter or a spark to light the burners. The hot surface igniter is a coil that lights red-hot much like an electric stove or a hot plate. The spark type is more like an igniter on a gas grill. If the igniter is burning red-hot or sparking then you know that you have the part working that will light the flame and that all of the pressure switches and limits are both working properly. If the igniter source is not working there could be a couple of problems going on. The first is the pressure switch that is pulled in when the inducer motor turns on. This will be connected to the inducer motor by a little black hose. if you turn off the unit and pull the hose of the inducer you can suck into the hose and see if you can hear it pulling in. If this seems like it pulls in easily and there is no blockage in the hose then you can go to this next step. Also, you can test the pressure switch with a multimeter and checking for continuity in the circuit. If pressure switch seems good, check for any little buttons on switches called disc limits. Press any button in the unit and see if a limit has been popped. If so retry the heating cycle and see if it turns on. At this point to check any further without a meter is not possible and you need to contact a heating repair company.

If the igniter is lighting the next thing that needs to happen is the gas valve turns on. If you can hear the valve turn on and there is gas coming out but not lighting the burners need to be cleaned. This is best left to a heating and cooling contractor due to the fact of possibly breaking the igniter and costing more in repairs in the future.

This is just a guide on things to check, so that you do not have a terrible sleep on the first cold nights of the year. However, we do not recommend do-it-yourself approach when the problem is serious.

I am a professional heating and air conditioning contractor in Chicago Illinois. This is an article for someone who has at least some experience with repairs to look through. If you feel that you can not handle the things that have been described please call a heating and air conditioning contractor to diagnose your system properly.

Chicago Heating Repair
3526 S. Paulina St. ChicagoIL60609 USA 
 • 773-234-4575

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