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I have a Goodman GMPN 120-5 Furnace that has been in service for 8 yrs. I have been running the blower 24/7 since installation. About a week ago the blower motor started shutting down on its internal over temp protection. After running, the motor is too hot to touch for more than a second. I have replaced the control board, motor and cap, put in new filter, checked A coils for plugging and they are not. Have let the furnace blower run with air venting below the A coil to be sure it was not loading the motor. Voltage checks out at 120V. The motor pulls about 7.3-7.5 amps on high speed and about 5.0 amps on the two slower speeds. The draw is up to 13 amps on start up. I have checked to ensure, when running, the motor only has one set of windings energized. The new motor is heating just like the original was. Don't know what else to check. Any ideas as to cause? The motor is adouble shaft double blower cage 3/4 HP 3sp 1075 rpm by GE. What are chances the new motor was defective out of the box? I am able to continue heating the house by running the blower on auto so that it only runs during the heat cycle and has time to cool down some between runs but the underlying problem still exists. I have checked and the motor is excessively hot after a relatively short run during a heating cycle.
Thanks Don
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Originally Posted by: db55047  I have a Goodman GMPN 120-5 Furnace that has been in service for 8 yrs. I have been running the blower 24/7 since installation. About a week ago the blower motor started shutting down on its internal over temp protection. After running, the motor is too hot to touch for more than a second. I have replaced the control board, motor and cap, put in new filter, checked A coils for plugging and they are not. Have let the furnace blower run with air venting below the A coil to be sure it was not loading the motor. Voltage checks out at 120V. The motor pulls about 7.3-7.5 amps on high speed and about 5.0 amps on the two slower speeds. The draw is up to 13 amps on start up. I have checked to ensure, when running, the motor only has one set of windings energized. The new motor is heating just like the original was. Don't know what else to check. Any ideas as to cause? The motor is adouble shaft double blower cage 3/4 HP 3sp 1075 rpm by GE. What are chances the new motor was defective out of the box? I am able to continue heating the house by running the blower on auto so that it only runs during the heat cycle and has time to cool down some between runs but the underlying problem still exists. I have checked and the motor is excessively hot after a relatively short run during a heating cycle.
Thanks Don Can you give all the numbers from the motor as well as any and all "Goodman" information such as full part numbers,model, serial.
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The furnace is a Goodman GMPN 120-5 serial #9805623032 installed 8-11-98. The blower motor is Goodman part #B13400-22. The motor is a GE Motors 5KCP39MG P876CS 3/4 hp 115 V 9.60 A 1075 rpm 60 hz 1 phase motor with a 15.00 MFD 370 V Cap. The motor is 3 speed.
Don
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Waiting for AM. Some friends work with the local Goodman distributor.
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Some additional questions.
Did you check the fan control center ? Also "Heating" should use a slower speed.
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The control board is new and the blower is on the slowest speed for "Heating". There isn't a really noticable difference between high speed and low speed when the wires are exchanged. What's the procedure to check out an AC CAP to be sure it is good?
Don
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Originally Posted by: db55047 The control board is new and the blower is on the slowest speed for "Heating". There isn't a really noticable difference between high speed and low speed when the wires are exchanged. What's the procedure to check out an AC CAP to be sure it is good?
Don I located the service manual for your unit. The wiring is as follows : Black on motor goes to Cool Terminal on module. Red on motor goes to Heat Terminal on module. Blue on motor goes to M 1 Terminal on module.
Capacitor Testing : Place the selector switch to "Ohms' on a Multi Meter.
Next place Red lead on one terminal and Black lead on the other.
It should rise, and slowly fall.
Rises and stays capacitor is shorted.
Stays on "zero" capacitor is open. :)
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Check the impeller on the combustion blower shaft.
I had similar headaches, blade is a friction fit on shaft, moves until it contacts inside of housing, then either overheats or shuts off completely. This will shut down the furnace or even prevent it from starting.
I took the fan housing apart and put a dab of epoxy on the shaft and impeller (after many other attempts to stop problem) to keep impeller from working its way to side of housing. this solved the problem.
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put an ammeter across the black wire while running on heat. If you get a reading then the motor is running on high speen in heat. You have a bad relay on the board. Check each speed while the motor is runing. It must be running on one speed at a time.
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My blower is duel shaft with a cage on each end the cages are locked to a flat on the shaft with a set bolt. The cages are not draging on the housing. The motor is running on the correct speed and does not have power to more than one winding at a time. I have checked this with a clamp on amp meter and by disconnecting the wires for speeds not in use. Motor still heats. I am currently having the blower cycle rather than run continuously and so far am getting by without thermal overload but this is a bandaid and not a cure for the problem. I may replace the motor under warrenty on the off chance that I got a bad one out of the box.
Don
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