February 21, 2008
Posted by bgkentucky

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You didn’t mention the manufacturer or size of your furnace. What you are describing is that your fan motor is running, however you have no ignition. There are many things that can cause this situation. In order to give you a quick overview of furnace operation, you must remember: The 4 Always Remember that you are working on a heating system and not just a furnace. A majority of furnace problems lie outside of the product itself. Therefore, when trouble-shooting a furnace problem, always check the following items before testing or replacing components. #1 - GAS PRESSURE The gas pressure should be set at a minimum of 11? W.C. with a minimum of 50% and ideally 100% of the gas fired appliances operating. You should test this pressure with a Utube Manometer only. If you choose to use a dial-type manometer, calibrate it often with a U-tube manometer. #2 - VOLTAGE Voltage to the furnace should be between 10.5 and 13.5 VDC during operation with the interior lights ON and OFF. This check should be made with the battery, converter or generator when applicable. Use a digital or analog multimeter when taking voltage readings. Do not use a test light. It does not provide enough useful information for proper diagnosis. #3 - DUCTING Always make sure that the furnace has at least the minimum number of ducts (not including closeable outlets) called out in the installation instructions. Check for proper duct connections at the furnace and heat registers, collapsed ducts and holes in the ducting. The duct runs must be as straight and tight as possible. The heat ducts must also be clean and clear of obstructions. #4 - RETURN AIR The return air passage should meet the minimum square inches as specified for the particular model of furnace in the installation instructions. This air passage should also be clean and clear of obstructions. Do not put air filters in this passage way. Also make sure that combustibles are not stored in the furnace compartment. ...I hope this helps..Giovanni

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February 21, 2008
Posted by bgkentucky

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Here's troubleshooting your problem...BLOWER RUNS - BUT FAILS TO IGNITE Low Voltage/High Voltage…Correct Power Supply (Battery) Gas pressure incorrect…Set pressure to a minimum of 11? W.C. with all appliances running. (Replace LP regulator if not obtainable). Furnace grounding wires not secure…Clean and secure grounds established Air intake restricted…Clean air intake. 12 volt polarity reversed..Correct polarity Motor running slow…Check voltage first. If 12 VDC while running, replace motor. Exhaust blocked…Clean exhaust. Combustion air wheel loose…Reposition and tighten. Sail switch defective or wire off…Reconnect wire or replace. Limit switch defective or wire off…Reconnect wire or replace. Edge connector on circuit board dirty…Clean with pencil eraser Circuit Board defective…Clean plug contacts. If still defective, replace. (check on board tester when possible). Gas valve defective…Replace valve or valve coil, depending on problem encountered. Main burner orifice blocked…Clean main burner orifice or replace. High tension lead wire defective…Replace wire Electrode out of adjustment…Adjust electrode (take care not to damage porcelain). Electrode defective…Replace Obstructed burner head…Clean burner head... Hope this helps... Giovanni

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February 21, 2008
Posted by BillAdams

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Can you hear the "sparker" trying to ignite the gas when you first power up the furnace? If not then find and check your sail switch. This is a switch with a arm that extends into the air box to ensure that air is blowing before the heater kicks in. If this switch fails it won't even try to spark. If the sail switch appears to work properly (test for showing open and closed condition) but there is no spark then it is more likely something related to the circuit board. If it's sparking but not igniting then look to propane problems or air flow first as the circuit board it trying to get things going. Are you out of propane?

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March 18, 2008
Posted by stevesandidge

( 0 ratings )

how about purging the tanks? it may be ya have a problem with your tank as well...if it is sparking that is

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May 09, 2008
Posted by coloradopete

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All of the previous posted solutions are good advice. I had your problem and found the high heat limit switch to be defective. This switch, on my furnace, is easy to access from the front of the unit, without removing the unit. I disconnected the wires from both sides of this switch and used a small piece of wire to jump the connectors, then tried the system. It fired immediately, which told me the switch was defective. I replaced the switch for about $20 and the unit has worked fine ever since.

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