Slow or failed starts. A gas ducted heater runs through a fixed start-up routine: the combustion fan purges the burner, the igniter sparks or glows, the gas valve opens and a sensor confirms there is a flame. When a Braemar clicks away and gives up, one link in that chain has failed. Typical culprits are a worn igniter, a flame sensor coated in residue, a pressure switch or a gas valve, and each is tested separately rather than swapped on a hunch.
Cool air after a warm start. The heater has protection that shuts the burner off if the heat exchanger gets too hot. A clogged return air filter, a blocked grille or a duct that has come apart starves it of air, it overheats, and the fan keeps blowing while the burner rests. Our guide to short cycling walks through the checks.
New noises. A whine that rises with speed is usually fan bearings; a rattle can be a loose panel or a duct touching a rafter; a deep rumble on ignition should be looked at quickly.