?flame sensing pilot or bad gas valve


Old 12-17-03, 08:07 AM
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?flame sensing pilot or bad gas valve

My 12 year old Carrier 58GP natural draft upflow 100,000 furnace is not igniting reliably. At first I thought it was the limit switch due to clogged filter, but it is not. The pilot lights immediately and the sparking slowly stops over several seconds. Then nothing happens and I think it goes into lock out due to 5 minutes of not "proving" the pilot. My question is how does the flame sensor work. I moved wires, and the thick orange wire going to the sparker fell out, so I firmly pushed it in. It cycled normally then. But I wonder if the "Proving" part of the pilot is old. There are three wires that go from the pilot light to the gas valve, and I think the pilot light/sensor assmbly may need replacing.
But there is also a time delay gas valve, White Rodgers 36E. It is possible that one time the pilot flame proved, and I think I heard the gas valve click, but no main burner after more than the usual several second delay.
I don't know if it could be the gas valve sticking or the flame sensor, but I'm pretty sure the flame sensor will be a lot cheaper. Is the pilot light/sensor a common reason for lock out? Is the gas valve reliable and seldom a problem?
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Old 12-17-03, 08:35 AM
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Hello: Mitchella

In a 12 year old heating unit with a flame sensor, replacing it first to determine if it is the direct cause of the problem is worthy. Cleaning the sensor often works. But may not if the original part is the same. Meaning never been replaced. Good service from it is the only indication.

Try removing the sensor and cleaning it with light weigth grit sand paper or steel wool. Check the connecting terminals and those the sensor attaches to as well as the sparking modules.

The sensor is the least expensive and easiest part to replace. Also the most likely to be the cause of the problem. Try these suggestions forst, then use the reply button to update the results.

An excellent source for original replacement parts is your local retail appliance parts store, the local heating dealers and agents retail part stores. Bring the make, model and serial numbers. The info will help to determine the possible problem causes.

Heating Agents & Appliance part stores stock replacement parts for almost every heater brand. The locations for the dealers, agents and retail part stores are listed in the phone book.

Be sure the electrical power to the appliance is turned off, the thermostat is turned down and the gas control valve is in the off postion before attempting any repairs. Always check for gas leaks whenever a repair includes any connection of a gas part, gas line or tubing or gas supply.

Retail parts dealers and heating part supplers can also help determine what the possible problem may be. Bring the make, model and serial numbers. Dealers are an excellent source for original replacement parts and are listed in the phone book.

Resident heating professionals replying within this forum, may have alternate solutions, suggestions, opinions and or test and repair methods. Check back on your question several times for additional replies.

Regards & Good Luck. Sharp Advice.
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Old 12-17-03, 01:58 PM
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what you describe is a typical failure of a carrier 3 wire pilot burner. replace it.

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