My heating unit will not stay lite. I can here it trying to ignite, but after about three tries it stops. Is there a fix? I just purchased a new thermstat

my heating unit will not stay lite. I can here it trying to ignite, but after about three trys it stops. Is there a fix? I just purchased a new thermstat
U did not mention what type of heating unit u have?.

Does you furnace have a standing pilot or does it use a hot surface ignitor??

Likely the thermostat has nothing to do with it. If the gas goes off only a few seconds after it comes on, it is the flame detector, a flat ceramic doodad near one of the gas jets. It should have a couple of wires going back to the control board. Sand it clean.

If the gas stays on a couple of minutes, and the blower doesn't come on, likely it is the blower relay. It is a little square metal doohicky on the control board. Giving it a rap with a screwdriver handle shortly after the gas comes on may start the blower. The problem will only get worse, meaning replacing the board.