During today’s visit, performed inspection and maintenance on one basement furnace unit. The customer expressed a concern that the furnace was not keeping up at night when it was cold outside. While inspecting the furnace, refrigerant could be heard running through the lineset. Upon inspection of the outdoor unit, found the outdoor unit running. There was not 24 V at the contactor. The contactor button was stuck in the closed position. This was allowing high-voltage to go to the compressor and fan, causing the system to run in both heat and cool mode. The system was essentially fighting itself. I was able to pull the contactor button back out to shut off the outdoor unit. Upon inspection of the contactor, it is not original to the outdoor unit and the company has no record of ever replacing it. An estimate has been sent to the customer to replace the contactor. There will be no warranty for replacing the contactor because it was not replaced by the company, therefore, the company canno