Problems with a Vehicle's Cabin Heat
During the winter, you'll probably rely on your vehicle's cabin heat to stay warm and comfortable. Temperatures can quickly drop during the latter part of the year. While some regions get cooler than others, most drivers use their vehicle's cabin heat during the winter. It will project warm air out of the vents, thus raising the cabin temperature.
The cabin heat, of course, should turn on when you adjust the climate control knob to the hot setting. There are instances, however, in which it may fail to produce heat. If your vehicle's cabin heat isn't working, you should investigate the problem so that it doesn't leave you freezing this winter.
One possible reason your vehicle's cabin heat isn't working is that the engine is still cold. Vehicles use different heating systems than residential homes and commercial buildings. When you turn on the cabin heat, a fan will blow air over a small and separate radiator, known as a heater core, to create hot air. Coolant will travel through your vehicle's engine where it picks up heat, after which it will travel to the heater core where this heat is released.
You won't feel hot air coming out of the vents immediately after starting your vehicle. If the engine is still cold, the coolant will be cold as well. As a result, the air coming out of the vents will be cold. Allow your vehicle to idle for five minutes so that the engine has an opportunity to warm up and, thus, produce cabin heat.
Low coolant can prevent your vehicle's cabin heat from working. The main purpose of coolant is to remove heat from your vehicle's engine, but it still plays an important role in heating the cabin. Coolant must flow through the heater core in order for your vehicle's cabin heat to work.
If your vehicle is low on coolant -- or if it's completely out of coolant -- you probably feel little or no hot air coming out of the vents. The fan may still work. With low coolant, though, the air won't be hot. You can check your vehicle's coolant by carefully opening the radiator cap while the engine is completely cold and inspecting the neck.
Even if your vehicle has plenty of coolant, the cabin heat may not work if the thermostat is stuck. The thermostat is an automated valve that rests between your vehicle's radiator and the engine. It's designed to open once the engine has warmed up and close when the engine has cooled down.
If the thermostat is stuck, coolant will remain stuck inside your vehicle's radiator. It won't be able to flow to the engine where it picks up heat, nor will it be able to flow to the heater core.