Most modern dishwashers will not activate the heating element unless the water going INTO the machine is 120 degrees. In other words, if the water isn’t ALREADY hot, the machine will NOT heat it up! This results in poorly washed dishes, and status lights (especially the “sani” light) flashing in warning.
If the water sitting in the pipes between your water heater and the dishwasher is NOT 120 degrees, it is very likely to cause problems. This means that, in cold weather, you MUST run hot water through the kitchen faucet BEFORE starting the dishwasher, to ensure that the water going into the machine is as hot as possible.
But wait, there’s more! Unfortunately, on some brands, such as Whirlpool, the machine will NOT turn the element back on until the machine is set through a diagnostic cycle. This means that even if you turn the machine on and off, and run hot water in the sink before starting it again, it will NOT WORK PROPERLY.
If your dishwasher isn’t heating up, call the manufacturer or an appliance repair company and tell them you need to run the diagnostic cycle. Do that FIRST, then run hot water in the sink and try it again. If it still doesn’t work, you’ll need to call a professional.