[roberco]

Hi,

Recently, the blower on my furnace is acting up weirdly. While the switches on the thermostat are set to ON and COOL, the blower kicks on for a minute or so than it shuts off for about 3 or 4 minutes. The blower then kicks on again and runs for a minute or 2 and then shuts off for 3 or 4 minutes. It keeps repeating this cycle since the last few days. My first thought was that the thermostat was bad. I went and replace the thermostat. No problem was seen for a few days. The blower and A/C worked fine. But the blower came back to the same OFF-ON cycling again. I suspected that I might have wired the thermostat incorrectly and tried to rewire the thermostat again. As I disconnected all the wire from the thermostat, the blower kicked on without the thermostat connected. Please give me some directions to fix this issue. Thanks.

[hvac1000]

Model and brand of furnace?

[roberco]

Thanks for answering my question. The furnace brand and model is: Lenox, C26-31. Just also want to let you know that the blower has been running constantly since yesterday after which I took the thermostat off the wall.

[hvac1000]

You have a stuck fan relay OR the thermostat wiring is shorted somewhere causing the blower to run all the time.

If that furnace has a circuit board that is another possibility.

Check the wiring first. Then look at the wiring diagram on the blower door to see if it has a separate blower relay.

This is another possibility.

If you have run your furnace in the heat mode lately it could be the high limit switch. If that switch trips it can cause the blower to run all the time as a safety measure.

[roberco]

Is there anyway that I can test if the compressor is still working? There are 4 colored wires coming out of the wall. They are red, blue, white, and green.

[hvac1000]

Actually there should be a yellow wire somewhere unless they wired your setup using non standard wiring colors. Try attaching red to green together this should activate the inside blower and the blower should run till the red and green are separated.

As far as the outside unit running the yellow and red (RC) should get the outside running BUT you do not have a yellow so I am hesitant to say.

If you can tell me the model number and brand of the thermostat you are using I can try to look it up to see if I can help with this.

Is this system a heat pump?

[roberco]

You know what, I would expect to see a yellow wire too. But I couldn't find it anywhere. By the way, this system isn't a heat pump. It's just a common central AC system. One thing that I still don't understand is that the blower is still running despite the fact that I already took the thermostat off the wall. IE, the Red and Green wire are not connected.

[hvac1000]

The blower relay is probably stuck. Look on the wiring diagram on the blower door to locate.

[hvac1000]

The blower relay is probably stuck. Look on the wiring diagram on the blower door to locate.