Nothing is more annoying than a heater that blows cold air - except maybe one that leaks. So if you're dealing with a heater problem, be it a leaker or one that doesn't seem to put out much warmth, keep reading because this article can help you solve your heater blues.

Before we get into troubleshooting heater problems, let's talk about the heater itself. The heater core is like a mini-radiator. It has inlet and outlet pipes and a finned copper or aluminum core through which hot coolant from the engine circulates. The heater core is located inside the HVAC plenum under the dash and usually on the passenger's side of the box.

When hot coolant from the engine flows through the heater core, the core gets hot and heats the air that's forced through it by the blower motor. Generally speaking, a heater should put out air that's at least 70° hotter than the outside temperature. So if it's 30° outside, your heater should put out at least 100° F.

The hot coolant flows from the engine to the heater core through the "inlet" hose. After circulating through the core, the coolant returns to the water pump through the "outlet" or "return" hose. Both the inlet and outlet return hoses should feel hot when the engine is at normal operating temperature and the heater is on.

In the inlet hose you may find a "heater control valve" that blocks the flow of coolant to the heater when the heater isn't needed (when running your ...