TempStar 90 plus furnace momentary shut down and restart in mid operation.

Plumboe

I have a Tempstar T9UHX100L201A 90 % furnace. I have noticed that mid operation the unit shuts down and quickly restarts. I have noticed it also happens during the cooling cycle and Heating cycle. While in the cooling cycle the unit including the condenser will shut down for three seconds and quickly restart. When in the heating stage I have notice the click of the thermostat disconnecting and quick initiating a call again. I have removed the wires from thermostat and installed a jumper lead to see if it would correct the problem it has not. Maybe someone has had a similar glitch. Thanks for you time.

HVACNUT

Since it happens in heat and cool modes, I would start with power. R and C. Check/tighten any splices and screw terminals. Check all grounds and neutrals. If that doesn't work, an ohmmeter is needed. 

Plumboe

Thanks I will give it a try.

mattmia2

check all the terminations in the line voltage wiring from the panelboard to the furnace and inside too to make sure one of those has not burned up.

JUGHNE

Printed circuit control board may have bad solder joints on the back side that over heat and open. After a little cool down and lack of vibration the joint closes again......if so you can usually see the burns on the back side....not always.

mattmia2

Or it was never soldered correctly to begin with. it is more likely you will see a crack in the solder that moves as you flex the board or components than you will see a burned spot, especially around the components with leads with more mass like the relays and the connectors where things connect to the board.