Lennox hs21-111. Fan blades are going the wrong direction, sucking air into the unit. How would this happen? Surely this hasn't been going on for the 10 years we have lived here. Wires on capacitor reversed, perhaps? Thank you.

you have a bad capacitor. Shut the power off to the unit, remove the electrical compartment cover, there will be a silver round thing with 3 wires going to it, one goes to the fan, marked fan on the capacitor one goes to C---also marked and the other to the compressor marked "HERM". Be sure to get the wires back in the same place. Before touching the capacitor take a screwdrive and touch the terminals together on each side to discharge the capacitor of any electricity it may be holding. I would wait on taking the old one off until you purchase the new one so that you can just easily switch the wires, once you have the new capacitor replace turn the power on and you should be set!!

Could you tell me the part number for the capacitor? It does not appear to be swollen. Easy to access. Hope I don't shock myself. Thanks.

Be sure to discharge the capacitor by jumping the terminals usually if you shut the power off to the unit and let it sit for awhile it will be ok. On the side of the capacitor there will be some numers like 45-5-370 vac..do you see any numbers like this? send me a message with the numbers and i'll tell you what you need.

There are no numbers visible on the front of the capacitor.

capacitors don't always swell when they are bad, trust me this is the problem. you should be able to purchase it at any hvac company or electrical supply warehouse

you may need to undo the strap, they may be on the back side.

I think I'll do that in the daylight. Thank you for your help. I'll get back on tomorrow.

not a problem, if no numbers are visable, just mark the wires and take it in to a supply company they should be able to figure it out. good luck! and let me know if you need anything else.