What’s Wrong with Your Car’s Heating & Cooling System?

What’s Wrong with Your Car’s Heating & Cooling System?

What’s Wrong with Your Car’s Heating & Cooling System?Do you worry about what’s wrong with your car’s heating & cooling system? If you have any concerns, bring your vehicle to Mountain View Automotive in Thornton. We can pinpoint the problem and get it fixed right away. Here, we’ll discuss a few things that may indicate there is trouble with the heating and cooling system such as blue or green discharge, clicking sounds, water vapor or bad smells, and much more.

When the air conditioning is not blowing cool air and the air from the heater is not warm, you automatically know there’s a problem. But what’s wrong with your car’s heating & cooling system is a bit more complex and may require the help of a professional to get it diagnosed, fixed and blowing the right temperature.

Refrigerant Leak

Many times a lack of coolant makes the air conditioner blow warm air. This means that the Freon or other refrigerants the compressor uses to evaporate heat is gone. It could be it just needs to be filled. If it’s recently been filled and it’s suddenly gone, you may have a leak. If it is a leak, you can’t just recharge the air conditioning system to fix it. 

Another way to tell is if the car AC doesn’t work and there is a colored discharge that looks blue or green, it is probably a leak. The color is from a UV dye which is added to the refrigerant to detect leaks easier.

If the air conditioning system has a leak, it’s called an open system. The leak needs to be repaired quickly or moisture will enter the system and cause damage. When the moisture and the refrigerant mix together, corrosive acids can destroy seals and components and cause a leak. Rubber seals and hoses can also lose their elasticity over time and break down, allowing refrigerant to escape and moisture to enter the air conditioning system. When moisture is present, it can damage the accumulator, receiver or drier because they remove moisture from the air conditioning system and even break if they are exposed to a leak or a crack.

We will need to find the leak, but that’s not always easy. The leak could be in the compressor, the evaporator, or the condenser. There is also a small metal can containing the desiccant, that needs to be changed if the system is opened. These parts of the car are not located near each other, so we can’t really just replace the whole air conditioner, like in one piece.

There are often several feet of hard and flexible lines that could be damaged and might be the cause of the leak. These lines can be evacuated and recharged. Then we can add dye to help us find the leak.

If it is a leak, we will make sure there are no electrical problems because a leak in the engine or electrical system could be dangerous and cause bigger troubles.

Heater Coil

If your heater doesn’t work, it could be a problem with the heating coil, even if it’s been flushed out. When you turn on the heater, it actually removes heat from the cooling system, so it cools the engine. It may need to be flushed again.

Some additional problems with a car heater and cooler could also be the compressor, the thermostat, the drain tube, the evaporator or heater core, the resistor stack or the climate control head. 


If you hear a clicking sound when the air conditioning is on, it may be a sign the compressor is not working. The air conditioning cools and dries the air, absorbing the moisture as it blows over the glass to clear the windshield. The clicking sound is made by a magnetic clutch turning the compressor on and off. The high or low limit switches may cause the compressor to cycle and temporarily shut off the compressor so it won’t be damaged. If you also hear the clicking when you use the defroster it may be low pressure in the compressor.


If your vehicle is not heating up it could be a malfunctioning thermostat. If it’s a cold day and the vehicle’s temperature display on your dashboard says the motor isn’t at its operating temperature and the air blows heat when the vehicle is idling but not when it’s moving, it probably means that the thermostat is stuck open.

Here’s what happens, the thermostat opens and closes, keeping the engine at the right temperature. If it breaks it will be stuck open or closed. When it is stuck open, the engine is slow to warm up and keep at the right operating temperature. When it is stuck closed, the engine can overheat because the coolant can’t get to the radiator. If the thermostat is the problem, it is cheap and easy to locate and fix.

Drain Tube

If there is a white mist or water vapor coming from your car’s vents and when you turn off the car there is no water dripping from the undercarriage, your drain tube is probably clogged and condensation is accumulating in the heating and air box. We need to unclog the tube.

Evaporator or Heater Core

If there is a bad smell of syrup or hot antifreeze and the windows fog up when you drive at night, there could be mildew on the evaporator or something wrong with the vehicle’s heater core.

Resistor Stack

If the car’s HVAC control speeds aren’t working or it won’t cycle between the settings, you may have a bad resistor stack which is located under the dashboard.

Climate Control Head

If the system is still working and blowing cool air, but there is a problem switching the air from vent to defrost, we may need to reset the climate control head.

There are many things to look at when we’re trying to find out what’s wrong with your car’s heating & cooling system, but our automotive experts at Mountain View Automotive in Thornton know what to look for. Our experienced ASE-certified technicians can fix all of your vehicle’s heating and air conditioning system problems. Our strange Colorado weather often requires using both heat and air conditioning during the same season. Let us help you get your heating and cooling systems working properly so you can enjoy a comfortable ride.