Heating System Repair

Auto Heater Repair in San Antonio, Auto Service Experts HVAC Services


Auto heating system repair at Auto Service Experts begins with complete diagnostics which allow our ASE certified technicians to pinpoint the source of the problem. When the heater blows cold air or fails to sufficiently warm the passenger area, it could be due to a problem within the engine, cooling system, or may require HVAC (heating, ventilation and air conditioning) system repair. These systems work together to transfer heat generated by the engine to the inside of the vehicle. If your car's heater is not working, have it looked at by a qualified mechanic right away (even if it's not cold outside). A problem in the cooling system can also cause damage to the engine, and severe overheating may result in having to have your motor replaced.


How do automotive heating systems work?

Engine & Cooling System

Heat within internal combustion engines is generated when fuel and oxygen inside the cylinders are ignited by the spark plugs. Once running, moving engine components rub against one another creating friction and more heat. The primary purpose of the cooling system is to prevent engine overheating, but it is also important in heating system operation. The thermostat regulates coolant temperature in order to maintain peak operating temperature in the engine. Once it reaches the proper temperature, the thermostat opens allowing coolant to circulate through the system in order to absorb and transfer excess heat. The water pump pushes hot coolant and water through the radiator which cools the fluid and allows heat to escape the vehicle externally. Coolant is also pumped into the heater core where the excess heat is directed into the passenger compartment through the HVAC vents.


Heating System Components

The heater core is similar in function to the radiator. It helps to reduce the temperature of engine coolant and transfers excess heat into warm air. While the radiator allows heat to escape outside the vehicle, the heater core transfers heat to the inside. The blower motor or fan pushes warm air from the core through the HVAC vents to the inside of the cabin. 


heater control valve replacement

Heater Control Valve Replacement


Some cars and trucks regulate temperature with a heater control valve located in a heater hose. When the driver adjusts the heater controls inside the cabin, the valve opens and closes to allow the proper amount of hot coolant to enter the core. This allows the air inside the core to warm up to the desired temperature before entering the cabin.


Others vehicles regulate temperature using heater doors in the HVAC case. HVAC doors (also known as blend doors) blend hot and cold air to reach the proper temperature and direct it through the necessary air vents. The movement of these doors is controlled by actuators which are operated by vacuum diaphragms or powered by small electric motors.


Car Heating Problems

The following are possible issues which can prevent the heater from properly warming the air inside the passenger compartment:

  • A leaking or clogged heater core
  • Damaged, cracked, or collapsed heater hoses - coolant cannot flow properly through the heater core, therefore heat cannot be directed into the cabin.
  • Air trapped within the core
  • Low coolant
  • Corroded or leaking water pump - If the water pump fins are broken coolant can not circulate through the system. This causes both the heating system and the cooling system to malfunction and can lead to major engine damage.
  • Bad thermostat - Repair this immediately! If the thermostat is stuck open, coolant will be continuously circulated and cooled and will not reach a high enough temperature to heat the cabin air. If it is stuck closed, coolant will not be allowed to circulate causing the engine to overheat and be destroyed.


Some of the most common HVAC repair services include heater core replacements, heater hose replacements, or blend door/heater control valve replacement. Heater core replacement cost can vary greatly between different makes and models of vehicles. In some vehicles, the core is relatively easy to get to, while others are located inside the dash and are much more labor intensive to access.


In some cases, auto cooling system repairs such as a water pump replacement or thermostat replacement are necessary to restore proper heater operation. Proper cooling system maintenance including regular coolant flushes and leak repair will help to prevent common heater problems and, more importantly, protect your engine!

Auto AC Repair

AC Repair on 04 Lamborghini Gallardo


Get your ride ready for the summer (and occasional mid-winter) heat! Auto Service Experts offers FREE AC checks by San Antonio HVAC specialists! Our mechanics are professionally certified in automotive air conditioning system repair & service, and are Experts in Diagnostics - We Save You Time & Money!

HVAC Blend Doors & Cabin Air Filter

This is an excellent illustration of how HVAC blend doors work to regulate the temperature and flow of air into the cabin. It also discusses services to sanitize and deoderize your auto ventilation system. Most vehicles are equipped with a cabin air filter which cleans the air flowing through the air ducts into the passenger compartment. Periodic cabin air filter replacements are necessary to prevent the filter from becoming clogged or contaminated. If the system becomes contaminated with dust, pollen, mold or microbes, it can cause a foul smell, worsen allergies, or even cause you to become sick!

ASE master technician Carlos Rodriguez

(210) 495-6688
Auto Service Experts

13050 San Pedro Ave. San Antonio, TX 78216

Mon-Fri 8:00am - 6:00pm