AC keeps running after desired temp is reached

Problems related to residential installations.

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AC keeps running after desired temp is reached

Post by BadKaram » Wed Jun 20, 2012 4:22 pm


In advance, thank you for any assistance you can provide.

- My HVAC system hates me...

The long and the short.

Older LUX Natural Gas/Central AC system, LUX 4 wire (Green, Yellow, White, Red)(RedH and RedC are jumper-ed together) Thermostat, this past week the AC (Outside) and the blower (inside) would keep running even after the desired temp has been reached. Thinking that this was an issue with the t-stat, I purchased a new one from (LUX) Lowes, installed, set up and turned on. AC comes on, house starts to cool down. Desired temp is reached in the house and the cooling system keeps on running. If I turn off the unit at the t-stat, AC and Blower both turn off. Assuming that I give the system the t-stat controlled 5 min timeline and turn it back on, system comes back online and runs, and runs, and runs, and runs........ While this keeps the house at a nice penguin temp, for the humans in the home its getting a little chilly.

Any advice as to what to look at next, or what to test to see where the problem may be?

Thank you much

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- AC keeps running after desired temp is reached

Post by heatseeker » Thu Jun 21, 2012 8:09 am

you have a crossed wire at the circuit board, or maybe even a crossed wire and stuck fan relay.

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