It isn’t unusual for a heat pump to ice-up in really cold weather, but it’s defrost cycle should kick on periodically to melt the ice. If the condenser unit of the heat pump is frozen up and the defrost cycle doesn’t melt the ice, turn it off. Make sure none of the return-air registers are blocked, and check the filter to make sure it isn’t clogged. If there doesn’t seem to be a problem with air flow to the unit, see more information at Heat Pump Cold Weather Problems or call an HVAC service professional.
Air conditioners can create a lot of water because they remove moisture from the air. To get rid of this, they have a [usually plastic] drain pipe that comes out of the side of the air handler. Over time, algae can block this pipe and, when it does, the AC won’t work. In fact, some condensate drains have a float switch that won’t let the AC run if water backs-up. Water can also puddle around the unit or flood the area. To deal with condensate problems, please see Air Conditioner Leaks Water, below.
Repair Clinic’s gas furnace troubleshooting guide will walk you through the steps necessary for diagnosing your furnace problem. Start with our list of symptoms. When you find the right one, we’ll show you the common causes. Enter your model number into the search field and you’ll know which part to buy. We can even show you how to install it. Where else can you find online furnace troubleshooting help like this?
In addition to the information below, see these two articles for the general care and maintenance of your air conditioner: Preparing Your Air Conditioner for Summer and How to Replace Furnace & AC Filters. Most noteworthy, you should replace the filters at least twice a year, before the heating and cooling seasons. For information on furnace problems, please see Furnace Not Working.