Nothing can be more disappointing than rushing into your car on a very cold weather only to find out that you have a malfunctioning heater. The vehicle's heating system diverts the heated coolant into the core, and a fan or blower blows through the core to deliver hot air into the engine compartment. Oftentimes, you don't realize how important this system is until the winter comes and you badly need the heating system to give you warm temperature inside the vehicle's cabin.
It's a good thing that problems with auto heaters don't always necessitate replacement. Sometimes, the issue can be easily resolved by topping up the radiator coolant. If you think your heating system has been acting up, you'd better diagnose the problem as soon as possible to prevent more serious troubles. Here are some ways to do that:
Look at the level of coolant in the radiator.
Park the vehicle on a level surface and while the engine is lukewarm, check the coolant level by removing the radiator cap. Since the engine is still a bit warm, you have to wrap a rag over the cap before grasping and loosening it to keep from being scalded. If the heater problems you are experiencing are caused by low coolant level, add the right amount of coolant. But if there's enough coolant in the radiator, proceed to the next step to troubleshoot further.
Inspect the system for leaks.
Now that you're sure that you have the right amount of coolant in the system and that it is running under correct pressure, check the system for leaks. Look at the heater's upper and inner hoses and inspect them for leaks and splits. There should also be no leak around the hose clamps as well as around the radiator.
Check for a blown fuse.
Start the engine and let it warm up. Turn on the heater and put it on the highest setting. Listen for the fan or blower to engage once you press the switch. If it doesn't work, you might have a blown fuse in there.
To inspect the fuse, locate the fuse box that's usually situated beneath the steering column. Check with the fuse diagram on the box to know which one is the fuse for the heating system. Take out the fuse and check if it's burned out or broken. Replace if necessary with a unit that's of the same amperage.
If the blower works, it's also possible that the hot air is just being misdirected. Perhaps, the heating system's small gates, which open and close to channel air, aren't working. Check these gates first before proceeding to the next step.
Check the heater core.
Raise the hood and look for the hoses connected to the core. These black or red hoses are usually positioned at the firewall. Place your hand above the hoses (do not touch them directly). They should be both hot enough to touch. If they aren't, it's possible that the coolant isn't circulating properly and it could be high time for you to replace the heater core.
Another way to check the core's condition is to get inside the vehicle and check the floor on the passenger side. If you noticed that it is wet and/or has a strong odor, you may have a leaking core that necessitates replacement.