Ok, the blower unit will run on heat and fan on. However when I switch to auto and cool the blower unit doesn't run. When I have the blower in the "on" position it will run until I switch the thermostat to cool. As soon as the unit outside comes on, then the blower shuts off and the outside unit keeps running. The blower will work on the heat setting also. I've never seen this happen like this. It is a Lennox brand outside unit and inside blower unit.

What could be the problem?

  • What model is your inside unit? Also, is this a heat pump system, or a straight air conditioner? Jul 2, 2017 at 3:20
  • The inside unit is Lennox as well as the outside
    – N.jon
    Jul 2, 2017 at 3:32
  • The unit is ac and gas furnace
    – N.jon
    Jul 2, 2017 at 3:34
  • 1
    Did you ever get this resolved? If so, please give a check-mark to the answer that helped you the most, or write up your own answer explaining what you did to get it fixed and give yourself a check mark. That will help others with this kind of problem know that this has a resolution and is a good place to look for their answer.
    – FreeMan
    Aug 20, 2020 at 15:58

2 Answers 2


The blower motor works on heat, That means your problem is in the ac unit or the thermostat

To determine if it's the thermostat you can use a couple bypass methods since the thermostat is just a bunch of hidden switches that eventually go bad, Run a piece of wire from the R terminal to the W terminal, that says you want heat on to the furnace without a switch, Then run that same wire from the RC terminal to the Y terminal, that's the method for your ac unit, if it kicked on then it's your thermostat, if it didn't then make sure you have 24 volts coming to your thermostat from the ac unit, if the ac unit don't have a transformer then you need a jumper wire from RC to R in your thermostat

Look in your ac units panel and make sure the switch is getting 24 volts on the both of the small wires and that there aren't any bugs stuck in the contacts, you should be getting 240 in and 240 out on the switch when it calls for cool air... also make sure to check the run capacitor, shut off the power, disconnecg the wires, touch the terminals with a metal screwdriver and a rubber handle to discharge it, then test it, herm to fan and herm to C for compressor, you do not want any under voltage at all, that would cause a higher amperage call when your fan is running at lower rpms

Also if you notice any bulging or oil on the capacitor unit itself that means it's bad.


The problem is either in the switch on the thermostat or the controls of the furnace unit.

You could try a new thermostat and if that does not work return it to the store for a refund.

Then call a certified Lennox service contractor. Troubleshooting the controls and electronics of an HVAC unit is a very advanced project even for an experienced DIYer. Not a project for novices.

Good luck!


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