While it might be the slide switch contacts if the thermostat it could also be the thermostat wiring or entire thermostat also. Remove thermostat cover and remove the 2 screws holding the thermostat to the wall. Carefully pull the wiring out the hole and make sure that the wire nuts are all tight and wiring is all connected. Small wires like that are brittle and can break off. If all is well you can push wiring back in the hole and resecure the thermostat to the wall.
Chris & Maria
2012 36RL, Full Body Paint, Dual Awning, Dual a/c, Splendide Combo, Fisher Paykel dishwasher, 6.5kW Onan, Goodyear G614's. 2015 F550 6.7l, 4X4, Lariat, CC, 176" WB, Long Box, B&W Companion