Why Is The Heat Not Working In My Commercial Vehicle?
It’s the issue no one wants: You get into your vehicle on a cold day, you turn on the heater for a comfortable blast of hot air, but only cold air comes out. Here’s what might be wrong and how to fix it, along with maintenance tips to help prevent this from happening.
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Why Isn’t My Vehicle’s Heater Working?
There can be several reasons why your vehicle isn’t sending warm air into the cabin. These can include a plugged heater core, a bad control valve, a malfunctioning thermostat, low coolant level, air in the cooling system, blend door actuator issues, dash control issues, or a faulty blower fan. Just when you need it most, a broken heating system can be one of the worst winter maintenance issues for trucks, and hopefully something that can be resolved right away.
How Does the Heater System Work?
It’s helpful to know exactly how your heater works. Coolant circulates through the engine to keep it from overheating. That fluid comes out of the engine at a high temperature and then travels to the radiator, where it cools down before it heads back into the engine. On its way from the engine to the radiator, it goes through the heater core, which looks like a miniature version of the radiator. The hot coolant heats the heater core, while a fan blows air over the hot core. That air heats up and is routed into the cabin to warm it up.
What Problem Can the Heater Core Cause?
Just like the radiator, the heater core can leak or clog up with deposits, and that reduces its ability to warm the air blowing over it. Cold air coming out of the vents can indicate a clogged heater core. If it’s leaking, you’ll likely smell coolant, or it will drip on the floor or the windows will stay fogged up. Replacing a core can be expensive because it’s often positioned deep in the dash, and the time and labor required to get to it makes it pricey. Flushing the vehicle’s coolant regularly, as per the scheduled maintenance, helps to protect the heater core.
What Problem Can the Heater Control Valve Cause?
Some vehicles use a heater control valve, which opens or closes to regulate coolant flowing into the heater core. If it’s stuck closed, coolant won’t get into the core and you won’t get warm air. A technician can check to see if this is the case, and if necessary, replace the valve.
What Problem Can the Thermostat Cause?
It’s important for an engine to come to its ideal operating temperature quickly so it runs at peak efficiency. The thermostat is closed when you first start your vehicle, preventing coolant from circulating into the engine so it warms up faster. Once the engine reaches operating temperature, the thermostat opens to allow coolant into it. If the thermostat fails and stays open, the engine won’t sufficiently warm up and the coolant won’t either. Therefore, the heater core won’t retain heat to keep you warm. If it sticks shut, the engine can overheat, which can damage it.
What Problem Can the Coolant Level Cause?
If the vehicle’s coolant level is too low, the heater core won’t get hot enough to warm the cabin. That lack of coolant can also cause the engine to overheat. Check the coolant level regularly and top it up as needed. If it’s frequently low, have the system checked for leaks. Maintaining the vehicle with scheduled coolant flushes and inspecting the hoses can help prevent this.
What Problem Can Air in the Cooling System Cause?
Air can get into the cooling system through a faulty radiator cap, any breaks or leaks, or if you run the engine when it’s low on coolant. It can also happen if the system wasn’t bled after a coolant flush by filling it, running the engine, and then topping it up once the air is out. The air bubbles can prevent the coolant from maintaining the proper temperature, including in the heater core. Have a technician inspect the system to find the issue and hire a trustworthy commercial vehicle mechanic to make a repair.
What Problem Can the Blend Door Actuator Cause?
The blend doors control airflow, including over the heater core, along with an inlet door that controls fresh or recirculated air flow, and a mode door that sends air to specific vents. If the actuator controlling these is faulty, air won’t warm up from the heater core or come out of the dash. Have the actuator checked and replaced if necessary.
What Problem Can the Dash Controls Cause?
While it’s relatively rare, the dash controls can sometimes fail, leaving you unable to control the temperature, the vent mode, or the fan speed. Have a technician diagnose and repair the issue.
What Problem Can the Blower Fan Cause?
Even if the heater is heating, it won’t do you much good if the blower fan isn’t blowing that hot air into the cabin. It could be that its motor has burned out, that there’s something wrong with its electrical connectors, or with some vehicles, the case could be a blown fuse. A technician will be able to pinpoint the problem.
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You need to be comfortable in your vehicle, so follow its maintenance schedule to help keep its heater in top condition. Pinpoint the problem with these common causes mentioned above and go with a trusted professional to make a fix.
Jil McIntosh
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