View Full Version : 1982 Model G11E Lennox Heating and Central AIr unit; Blower running slow
jrny42
Jul 9, 2010, 02:25 PM
Air was on working fine, noticed it had stopped, went into furnace room and found water on the floor, (coming from under furnace, in motor compartment) obviously and icing condition. Took care of water let it thaw all night now blower motor is running very slow, capacitor is good on motor, motor about a year old. Did I fry it? Could the capacitor in the outside unit be bad?
Thanks any input would be great
hvac1000
Jul 9, 2010, 03:59 PM
The only capacitor that counts is the one for the motor inside. You said that was good so I guess you have a real motor capacitor checker or you used the calculation tool like this.
Note the test is good for any motor capacitors not just compressors.
Unfortunately, some capacitor checkers we use in the field are ineffective at testing for a bleeding/leaking capacitor because there is no load on the capacitor at the time that it's being tested.
The good news is that there is a fairly reliable way to test a capacitor under load.
While the compressor is running, measure the ac voltage across the run capacitor. You will be reading the voltage that the compressor/motor is generating. The term for this is “back electromotive force.” Measure the amperage being drawn through the start wire between the capacitor and the compressor start terminal.
Be sure to keep your amp meter away from the components in the control box - that could distort your reading. Use the voltage and amperage readings you've obtained in the following formula:
Amps X 2,650 ÷ Voltage = Actual microfarads.
If the solution to your test gives you a microfarad rating that is 5% below the capacitor's labeled rating, be suspicious and replace it. It makes no difference if a capacitor is new or 20 years old since there is no exact time or usage that the capacitor goes bad at.
jrny42
Jul 9, 2010, 04:07 PM
By the way thanks for the reply!
hvac1000
Jul 17, 2010, 04:36 PM
Air was on working fine, noticed it had stopped, went into furnace room and found water on the floor, (coming from under furnace, in motor compartment) obviously and icing condition. Took care of water let it thaw all night now blower motor is running very slow, capacitor is good on motor, motor about a year old. Did I fry it? Could the capacitor in the outside unit be bad?
Thanks any input would be great
Check and make sure the air filter is clean or just replace it. Also make sure all registers are open.
My thoughts are the air flow restriction can also seem to make a motor run slow since it cannot find enough available air to move especially if the filter is plugged up. It is also a possibility that the circuit board if so equipped could have got some water damage and is causing a problem with the motor speed selection.
There are many items besides just the motor or capacitor that can cause a air flow problem. If you unit is older it is also possible that the indoor coil for the A/C unit has a mat of dirt on it on the air entering side. If that gets wet it can really slow down the air movement. Happy Hunting.