HVAC Service Tips

Carbon Monoxide and gas detection saves lives The following information will help you understand the importance of your heating and air conditioning system and how we can help you maintain it:


If you have a furnace or air conditioner that is not working, here are a few tips that you can do before giving us a call.

Furnace Not Working

There are many things that you, the home owner, can do before calling us out to fix your furnace. Most of these things are fairly easy to perform.

  1. Be sure that the filters are clean.
  2. Check thermostat program settings for proper temperature, etc.
  3. Check thermostat to see that it is in the heat mode and the fan is on auto.
  4. Check/change batteries in thermostat.
  5. Check to see if the gas valve is on. (One inside the furnace and one outside)
  6. Check electrical panel box for tripped or partially tripped breaker.
  7. Check fuse on furnace circuit board.
  8. Furnace cover panel on the blower door "Blower Door Safety Switch" depressed by cover panel.
  9. Depress limits/safety switches applicable to your furnace.
  10. Unplug furnace for several minutes and plug back in (this often resets a furnace with a problem).
  11. Be sure all floor and/or ceiling supply registers are open.
  12. Restrictions in furnace vent pipe (local birds haven’t made a nest there).

Below are a few different diagrams that will help you locate some of the items we just mentioned.


  1. Relief Box
  2. Rating Plate
  3. Gas Valve Control Knob or Electric Switch (On/Off)
  4. Gas Valve
  5. Gas Burner
  6. Flame Sensor
  7. Air Filter Retainer
  8. Air Filter
  9. Blower and Blower Motor
  10. Draft Safeguard Tube and Switch
  11. Gas Manifold
  12. Manual Reset Limit Switch
  13. Hot Surface Ignitor
  14. Blower Door Safety Switch
upflow furnance


  1. Manual-Reset Auxiliary Limit Switch
  2. Blower and Blower Motor
  3. Relief Box
  4. Gas Valve Control Knob or Electric Switch (On/Off)
  5. Gas Valve
  6. Gas Burner
  7. Rating Plate
  8. Blower Door Safety Switch
  9. Draft Safeguard Tube and Switch
  10. Gas Manifold
  11. Manual Reset Limit Switch
  12. Hot Surface Ignitor
  13. Flame Sensor
downflow furnace

Gas Valve On/Off

Knob Type:

Switch Type switch type
Outside of Furnace outside of furnace
Limit / Safety Switch limit / safety switch
3 Amp Fuse 3 amp fuse