"False Starts" for furnace


Old 12-29-01, 12:21 PM
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Question "False Starts" for furnace

First of all, please forgive my lack of terminologoy. We're having problems with our furnace, and I'll do my best to describe the problems. The local-yokel furnace repairman has been here three times, and nothing is helping!

What happens is: the burner kicks on (I call it the pre-humming). Then, it will suddenly shut off before the furnace starts. Then, the humming starts again, and shuts off before the furnace comes on. This will go on for 2 - 6 times before we finally (Thank God), get heat. So basically, it's "hum, stop. Hum, stop. Hum, stop", and then fan comes on and we get heat.

The furnace repairman has cleaned the furnace, replaced the injector (oil burning furnace), and then replaced the transformer. The third time out here, though, it wouldn't do the shutting-off thing for him. He says "maybe" it's the fan motor switch, but that if it WAS broke, we'd get no heat at all. We're stumped, and inexperienced.

My husband hit the "reset" switch inside the furnace once, but it still does the same darn thing.

Any ideas on what we can do? Keep in mind that the injector and the transformer have already been replaced.

Thank you in advance for your thoughts.
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Old 12-29-01, 01:04 PM
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Arrow ....Several Problem Possibilities

Hello Vixrofo. Welcome to the Heating and Cooling Appliance forum and the Do-It-Yourself Web Site.

The first thing to do is call the "Local-Yokel" get any $$$ already paid returned. Then check your phone book to locate a real service person who knows about oil burners and has experience with these types of units.

There could be 1 or more of several possibilites as listed below:

Defective Glow Coil: {If equipped with one}
The glow coil may glow but just be too weak to allow current to continue to flow to the coils. The solenoid coils are also part of the electrical loop and may effect proper glow coil operation or functioning.

Defective or poorly grounded Spark Igniton Module.

Defective Gas Valve Solenoid:
The gas valves solenoid is internal.
Take the entire gas valve unit to your local appliance parts store and have the entire assembly and parts tested.

Defective Gas Valve:
Remove entire unit as an assembly. Take the entire assembly to your local appliance parts store for testing. Gas valves are not repairable. Replacement is the only option if defective.

CAUTION: Do Not attempt to repair the gas valve! This is a non repairable item!

If the burners are cycling on and off, most likely it's cycling because the flame sensor element is dirty, defective or has a faulty connection.

Possible the fan ON switch is defective.
Could be the high limit switch is defective.
The fan motor itself could be overheating.

The fans squirrel cage bearings could be dragging and causing the fan motor to overheat. Try oiling the motor bearings and the squirrel cage bearings.

The bearings are located on the ends of the motor and the ends of the fan cage and may have oiling caps, which need to be lifted up. Add a few drops of any type of oil that is available.

The do-it-yourself person can do electrical tests and continuity tests on several of the parts mentioned above. There are parts such as solenoids, gas valves, etc. when neither electrical tests and continuity tests will provide proof positive the part is actually functioning correctly. Therefore, do not rely solely on either test.

The only positive proof any part is functioning correctly, is to carefully remove the part or parts you suspect to be the potential problems, and have the local appliance parts store personnel run the required tests.

Appliance parts dealers carry replacement parts for all appliances and are listed in the phone book under appliances. Electric motor repair shops can either fix, rebuild or replace the heaters existing motor. Shops also listed in the phone books.

Read the manufacturers online web site for product information, problem solving methods, disassembly, reassembly methods, repair proceedures and instructions, pictorials and schematics, which may be available online.

Read the RECENT & ARCHIVE postings, within this forum, for other questions on this topic and the replies offered.

Regards & Good Luck
Tom_Bart....TCB4U2B2B.....Company Enterprises
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