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How To Repair Oil Furnaces

How To Clean the Oil Furnace Stack Control

The stack control of the oil furnace, located in the stack, is a safety device that monitors the operation of the oil burner. If the burner fails to ignite, the stack control shuts off the motor. Frequently, however, a furnace shutdown is caused by a malfunctioning stack control rather than by the burner.

What You'll Need
You'll want to have these tools on hand to check the stack control:
  • Wrench
  • Brush
  • Soapy water
  • Soft cloth
  • Newspaper
  • Refractory cement
If the burner fails to ignite, first check the fuel tank and refill it if necessary. If the tank doesn't need to be refilled, press the reset button on the stack control. If the burner doesn't ignite after you've pressed the button once, clean the control, as detailed below. Then press the reset button again. If the burner still doesn't operate, call a professional service person.

The stack control gradually becomes coated with soot during the heating season. To keep it working properly, clean the control every month or as soon as it becomes soot-covered. Here's how to clean the stack control:

Step 1: Remove bolts that hold control in stack. Pull out sensor and its housing.

Step 2: With brush dipped in soapy water, remove all soot from control. Wipe control dry with soft cloth.

Step 3: Before replacing control, clean stack. Spread newspaper to protect floor, then disassemble stack. As you work, remove soot and debris from each section by tapping them firmly on newspaper-covered floor.

Step 4: After cleaning sections, reassemble them in reverse order. Make sure stack sections are properly aligned and firmly connected.

Step 5: Finally, reposition stack control in stack, and reseal connection to chimney with refractory cement.

To remove the stack control, turn off the power to the furnace, then back out the bolts.
© 2006 Publications International, Ltd.
Clean the stack control every month. To remove the control, turn off
the power to the furnace, then back out the bolts that hold it in the stack.

Some oil furnaces have an electric-eye safety switch instead of a stack control. This switch serves the same function as the stack control. If the burner has an electric-eye safety, remove the access cover over the photocell; it is held by hooks or retaining screws. Wipe the cover clean to remove accumulated soot. Reassemble the switch, replace the cover, and turn the power back on. If the burner still doesn't ignite, call a professional service person.

If the stack control or electric-eye safety switch is especially dirty, the furnace may not be properly set to burn the fuel completely. In this case, call a professional service person for adjustment.
Caution: Do not attempt to replace these controls yourself.

You can, though, set the switches, which must be ON for the furnace to operate. Find out where they are located on the next page.

For more articles on home repair, check out the following links.
  • Furnace Maintenance: Save yourself time and money by learning the steps to keep youor furnace in prime condition.
  • Major Appliance Repair: If the furnace isn't the only thing in your house on the fritz, you can learn how to fix other machines in this article.
  • Small Appliance Repair: Once you've tackled the furnace, a toaster or blender seems like child's play. Find out how to fix them here.
  • Thermostat Maintenance: To make sure there's actually a problem with your heating system, you may want to check the thermostat, too. Learn how to calibrate a thermostat.