Learn how to troubleshoot and repair your furnace.
When your heating system acts up, there are some things you can do to either fix or test it. If these suggestions do not seem to work, or if it sounds too complicated, call a reliable repair man.
Forced air systems
These usually have a fan and limit switch mounted on the supply plenum or on the furnace near the plenum. Temperature makes the switch react turning the blower on and off and shutting down the furnace before it overheats. If the blower short cycles--that is, turns on and off often--adjust the switch's fan control to widen the spread between the blower's start and stop temperatures. Don't set temperatures too low or it may come on during the summer.
Balancing a forced air system
To get each room at the comfort level you want, distribute thermometers throughout your house in the center of each room. Set the thermostat at 68 degrees and start the system. Make sure all registers and dampers are fully
open. After 30 minutes, close registers or dampers as needed until each room is at the desired temperature. This is a trial and error process that might take a day or so. When finished, mark the handle or lever on the registers or dampers.
A burning pilot flame or an electric igniter lights the burner, which is thermostatically controlled. A thermocouple senses heat and only allows gas to flow when enough heat is present for combustion. Ignition problems and clogged burners are usually the reason for furnace troubles. Clean burner tubes yearly. To clean:
a. Remove tube (this can be done in most furnaces).
b. Shut off gas and power.
c. Unscrew tubes from supporting bracket (some are not screwed on).
d. Gently twist and lift tubes free.
e. Brush or vacuum tubes to clean them; avoid damaging burner ports.
f. Carefully clear any clogged ports with a stiff wire.
g. Replace tube.
Pilot and burner flames
If the pilot won't stay lit, make sure the flame is lapping over the end of
the thermocouple. If not, adjust it.
To adjust the pilot flame:
a. Remove any cap covering the pilot adjusting screw on a combination control.
b. Turn screw counterclockwise to increase flame or clockwise to decrease it.
c. Flame should envelop thermocouple bulb by one-half inch and be dark blue with a slight bit of yellow at the tip. If necessary, clean the pilot opening with a toothpick if the flame flickers or won't stay lit.
To burn efficiently, burners may need their air intake adjusted:
a. Loosen any locked scre.w
b. Open air shutter until flame lifts from tube.
c. Close shutter until flame settles back and is correct color.
d. Retighten screw.
To relight the pilot:
a. Turn gas knob and main electric switch off.
b. Lower thermostat.
c. Let gas dissipate.
d. Then turn gas knob to pilot.
e. Depress and hold in reset button and light pilot.
f. Hold button in for one minute, then release.
g. If pilot goes out, repeat, holding button in longer.
h. When pilot stays lit, turn knob on.
i. Turn on current and raise thermostat.
Call a reliable service technician for more serious problems.