Gas and Oil Home Heating Furnaces - furnace probelms
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11-11-01, 06:58 AM
Janitrol model #gmp075-3
The blower will kick on and stay on but the burners cut on and off. After two cycles of doing this it shuts down. This has been going on for two winters but it does not always continue to do this for weeks. Sometimes it will go on for a day, a week or now a couple weeks. This will happen throughout the winter thou. The thermastat has been changed but both old and new, still the same probelm.
The blower will kick on and stay on but the burners cut on and off. After two cycles of doing this it shuts down. This has been going on for two winters but it does not always continue to do this for weeks. Sometimes it will go on for a day, a week or now a couple weeks. This will happen throughout the winter thou. The thermastat has been changed but both old and new, still the same probelm.
Sharp Advice
11-12-01, 04:33 AM
Hello tweir28. Welcome to the Heating and Cooling Appliance forum and the Do-It-Yourself Web Site.
Based solely upon the limited information you posted, one of the most likely causes is a restricted intake air supply or warm air flow thru the ducting and or to and though the registers in the rooms.
If the air filter is clean, all the registers are opened, it's possible the A/C coils are clogged with lint and dust if the unit has A/C. The ducting may also be collapased, etc. Could be a piece of furniture is too close to the intake air supply, defective blower motor that spins too slowly or any of many other air flow problems.
The above conditions will still allow the fan to run but the restricted air flow causes the furnace to overheat internally which then activates the high limit safety switch which in turns cycles the burners off until the firebox cools down some.
Defective gas valve solenoids may also be the cause.
A bad or poor grounding in the ignition system.
A restricted flue.
Other possible causes:
Defective Glow Coil:
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 Solenoids:
There are two...both are on top of the gas valve.
Solenoids also supply voltage to the glow coil and are part of the electrical loop. 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!
Flame Sensor:
This part is located on the burner or near the pilot assembly. If it's defective, it will cause the glow coil to not function or cause the problem your discribing. You can test this part with a continuity tester or an ohm meter. However, do not soley rely on this test to prove the part is functioning correctly. Cleaning it may solve the problem.
FYI:
The do-it-yourself person can do electrical tests and continuity tests on several of the parts. There are parts such as flame sensors, timers, solenoids, gas valves, etc. when neither of these tests will provide proof positive the part is actually functioning correctly. Therefore, do not rely solely on either test.
TIP:
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 person run the required tests.
Appliance parts dealers carry replacement parts for all appliances and are listed in the phone book under appliances. Refer to the manufacturers online web site for additional product information, problem solving methods, pictorials drawings and schematics, should they be available.
Check the ARCHIVES, within this forum, for other postings on this topic and the replies offered.
Regards & Good Luck
Gas Appliances Forum Moderator
Tom_Bart.... Enterprises
Energy Conservation Consultant & Natural Gas Appliance Problem Diagnostics Technician.
Based solely upon the limited information you posted, one of the most likely causes is a restricted intake air supply or warm air flow thru the ducting and or to and though the registers in the rooms.
If the air filter is clean, all the registers are opened, it's possible the A/C coils are clogged with lint and dust if the unit has A/C. The ducting may also be collapased, etc. Could be a piece of furniture is too close to the intake air supply, defective blower motor that spins too slowly or any of many other air flow problems.
The above conditions will still allow the fan to run but the restricted air flow causes the furnace to overheat internally which then activates the high limit safety switch which in turns cycles the burners off until the firebox cools down some.
Defective gas valve solenoids may also be the cause.
A bad or poor grounding in the ignition system.
A restricted flue.
Other possible causes:
Defective Glow Coil:
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 Solenoids:
There are two...both are on top of the gas valve.
Solenoids also supply voltage to the glow coil and are part of the electrical loop. 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!
Flame Sensor:
This part is located on the burner or near the pilot assembly. If it's defective, it will cause the glow coil to not function or cause the problem your discribing. You can test this part with a continuity tester or an ohm meter. However, do not soley rely on this test to prove the part is functioning correctly. Cleaning it may solve the problem.
FYI:
The do-it-yourself person can do electrical tests and continuity tests on several of the parts. There are parts such as flame sensors, timers, solenoids, gas valves, etc. when neither of these tests will provide proof positive the part is actually functioning correctly. Therefore, do not rely solely on either test.
TIP:
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 person run the required tests.
Appliance parts dealers carry replacement parts for all appliances and are listed in the phone book under appliances. Refer to the manufacturers online web site for additional product information, problem solving methods, pictorials drawings and schematics, should they be available.
Check the ARCHIVES, within this forum, for other postings on this topic and the replies offered.
Regards & Good Luck
Gas Appliances Forum Moderator
Tom_Bart.... Enterprises
Energy Conservation Consultant & Natural Gas Appliance Problem Diagnostics Technician.