AC & Heating Systems

Car & Truck AC & Heating Systems

A/C Compressors & Systems Repair/Replacement

AC Compressors and their assistive components work together and comprise your vehicles AC system. All the components of the system must be operating correctly to provide you the comfort that we are all accustomed. These are the main components and how they work:

The Compressor

The compressor used to air condition your car works in a similar way to the one in the refrigerator in your kitchen. The job of the compressor is to move liquid refrigerant around in a pipe. The compressor pumps, or forces, the liquid from the evaporator into a condenser and expansion valve, and then back to the evaporator.

The engine drives the compressor with a belt. In action, the compressor takes the low pressure refrigerant from the evaporator and compresses it according to speed and air temperature. The inlet side is known as the low (pressure) side and the outlet side is known as the high (pressure) side. The compressor compresses the refrigerant, and raises its temperature higher than that of the surrounding air. Then, the compressor forces the refrigerant into the condenser.

Compressor Clutch

The air conditioning compressor has an electromagnetic clutch that can engage or disengage the compressor pulley. The compressor pulley always turns when the engine is running, but the compressor only runs when the pulley is engaged to the compressor driving shaft. When this system is activated, current runs through the electromagnetic coil. The current attracts it to the armature plate. The strong magnetic pull draws the armature plate against the side of the turning pulley. This locks the pulley and the armature plate together; the armature plate drives the compressor. When the system is deactivated, and current stops running through the electromagnetic coil, flat springs pull the armature plate away from the pulley.
The magnetic coil does not turn since its magnetism is transmitted through the pulley to the armature. The armature plate and hub assembly are fastened to the compressor drive shaft. When it’s not driving the compressor, the clutch pulley turns on a double row of ball bearings.

AC Compressor Drive Ring

Inside the air conditioner’s refrigerant compressor is a drive ring made of a friction material that is mounted to both sides of the “swash” or “wobble” plate. As the swash plate rotates, the friction material pushes the ball bearings (mounted to the pistons) back and forth.

The Condenser

The condenser is a long tube that goes back and forth through a multitude of cooling fins, quite similar to the evaporator in structure. The condenser is mounted in front of the radiator to take advantage of the forced air provided by the fan and the motion of the car.

As the highly pressurized refrigerant (vapor) flows into the condenser, it gives off heat and warms the condenser. This causes the condenser to be hotter than the forced air coming through the condenser. The condenser hands its heat off to the forced air and turns the refrigerant back into cool liquid in the expansion valve, where it heads back to the evaporator.

The Evaporator

The evaporator is a long tube, or coil, that goes back and forth through a multitude of cooling fins. It is quite similar to the condenser in structure.

The refrigerant is a liquid when it enters the evaporator. A fan blows warm air over the evaporator. The warm air causes the liquid refrigerant to boil. This means that it absorbs the heat from the warm air. Once it has absorbed the heat from the warm air, the warm air isn’t warm anymore. The same blower that blows the warm air (that is now “cool” air) over the evaporator, keeps on blowing it into the interior of your car, and you have — air conditioning! The evaporator also removes the moisture from the air coming through its fins and turns it into water. The water just drains off.
The temperature of the evaporator coil can go from 33 degrees F to 0 degrees F. If it goes below 32 degrees F, the moisture that’s supposed to drain off the coils will freeze. This makes for a very (surprise!) inefficient system, so a thermostatic switch is used to connect and disconnect it to the compressor as necessary.

Expansion Valve

The expansion valve determines the correct amount of refrigerant going into the evaporator, and it lowers the pressure of the refrigerant.
When the compressor starts, the expansion valve opens and the liquid refrigerant flows through a strainer in the high pressure liquid inlet. Once in the expansion valve, the refrigerant is correctly pressurized. As the evaporator calls for more refrigerant, the expansion valve allows the required amount of low pressure liquid refrigerant into the coils.

The expansion valve maintains the delicate balance between the heat load and the cooling efficiency of the evaporator.

Discharge/Suction Service Valves

Discharge and suction service valves allow the air conditioning system to be emptied and filled. These valves also provide places where the system can be checked with pressure gauges.

Note: Some systems use a Schrader valve in place of the discharge and suction valves. This is a spring-loaded valve which looks rather like the valve in a tire.

The Compressor Relay

A capillary tube from a cycling switch lets the switch know what the temperature is in the evaporator. This switch turns the compressor on and off to keep the evaporator temperature at about 32 to 45 degrees F. The relay switch keeps moisture from freezing on the evaporator core.

Electric Air Conditioning Fan

Sometimes an extra electric fan is placed in front of the condenser to provide an extra flow of air during warm weather, or for times when the car has to idle for a long time. You activate and deactivate the air conditioning fan when you turn it on and off at the control panel.
As you can see there are many components working together to keep us cool. AC systems must be evacuated and charged only using appropriate tooling designed to prevent environmental contamination and damage to your system. Only certified technicians should work on your AC system.

A/C Recharge & Leak Diagnostics

A/C Hoses & Lines

Evaporator Cores: The Evaporator

The evaporator is a long tube, or coil, that goes back and forth through a multitude of cooling fins. It is quite similar to the condenser in structure.

The refrigerant is a liquid when it enters the evaporator. A fan blows warm air over the evaporator. The warm air causes the liquid refrigerant to boil. This means that it absorbs the heat from the warm air. Once it has absorbed the heat from the warm air, the warm air isn’t warm anymore. The same blower that blows the warm air (that is now “cool” air) over the evaporator, keeps on blowing it into the interior of your car, and you have — air conditioning! The evaporator also removes the moisture from the air coming through its fins and turns it into water. The water just drains off.
The temperature of the evaporator coil can go from 33 degrees F to 0 degrees F. If it goes below 32 degrees F, the moisture that’s supposed to drain off the coils will freeze. This makes for a very (surprise!) inefficient system, so a thermostatic switch is used to connect and disconnect it to the compressor as necessary.

A/C Condensers

The condenser is a long tube that goes back and forth through a multitude of cooling fins, quite similar to the evaporator in structure. The condenser is mounted in front of the radiator to take advantage of the forced air provided by the fan and the motion of the car.
As the highly pressurized refrigerant (vapor) flows into the condenser, it gives off heat and warms the condenser. This causes the condenser to be hotter than the forced air coming through the condenser. The condenser hands its heat off to the forced air and turns the refrigerant back into cool liquid in the expansion valve, where it heads back to the evaporator.

Expansion Valves

The expansion valve determines the correct amount of refrigerant going into the evaporator, and it lowers the pressure of the refrigerant.
When the compressor starts, the expansion valve opens and the liquid refrigerant flows through a strainer in the high pressure liquid inlet. Once in the expansion valve, the refrigerant is correctly pressurized. As the evaporator calls for more refrigerant, the expansion valve allows the required amount of low pressure liquid refrigerant into the coils.

The expansion valve maintains the delicate balance between the heat load and the cooling efficiency of the evaporator.

Heater Cores

You don’t want your car’s heater core to die before winter. The core is what warms the air when you turn up the temperature. It also keeps the defroster’s air warm so it can keep your windshield and your visibility clear; well, as clear as possible depending on the weather conditions outside. Stringer Auto Repair can inspect your core to make sure it’s okay. Here are five signs it isn’t.

Fog Inside Your Car

Two things could be going on if you have fog inside your car. First, the heater core could be malfunctioning and, as such, the defrosters aren’t working. Second, the core could be blowing fog/smoke into your vehicle’s cabin. Both are bad signs and need to be checked into right away.

Sweet Smells in the Car

The sweet smell in your car might not be your perfume or the donuts you’re taking to work. It could be the heater core. If the heater core is leaking, it will blow the odor of engine coolant through the vents. Coolant smells sweet, almost musty. Many people say it smells like candy, fruit, or maple syrup.

Constant Engine Coolant Loss

Speaking of coolant, another sign your core is going bad is coolant loss. This usually happens because there is a coolant leak in the heater core. You may top off your coolant only to find it low again the next day. Low coolant can overheat and damage the engine, so it’s important to fix the leak ASAP.

Cold Air in the Cabin

The heater core has tubes that circulate hot engine coolant through them before the coolant is returned to the radiator. Air blows over the hot coolant to warm it before it’s blown through your vehicle’s vents. If the air is cold instead of hot, your core might be leaking all of the hot coolant out of the tubes.

Cold Cabin/Hot Engine

Finally, the last sign your heater core is going bad is a combination of the previous two signs. If you’ve got cold air blowing through the vents but your engine is overheating, you’ve got a coolant problem that can likely be traced back to the core. It’s probably leaking and starving the engine or coolant.

Actuator Replacement

The AC actuator moves air distribution doors to two or more positions to direct air flow for heating and A/C vents. The AC actuator is located underneath the dashboard attached to air distribution doors in the HVAC box.

Doors can control warm air/cold air blending, recirculated/fresh air control, or dual zone splitting. The motors can move the doors into many different positions, or just two.

If your vents are not blowing when you command them, or they make a clicking noise when actuated, you probably have an actuator not working or going out. They are very often located in hard to reach locations.

Heater Hoses

During the cold winter months, your heating system must be working properly. One vital part to your vehicle’s heating system is its heater hoses. Before we cover what exactly heater hoses are and what they do, we should understand how your vehicle’s heating system actually works. It may seem surprising, but your vehicle’s heating system actually works off your engine’s cooling system. When your engine is running, it produces tremendous amounts of heat. This heat needs to be transferred away from the engine so the engine doesn’t overheat. Engine coolant, called antifreeze, travels throughout the engine absorbing the excess heat and transports it out of the engine. Then, basically what your heating system does is it uses the excess heat from the engine to heat the inside of your vehicle. Some of the engine’s excess heat will travel to the radiator and will be released into the atmosphere. However, some of the excess heat also travels to the heater core (the heater core, located inside your dashboard, is in charge of heating your vehicle). This is where heater hoses come into play. Heater hoses are used to transfer the excess heat, in the form of engine coolant, from the engine into the heater core. Once the heated engine coolant reaches the heater core, it travels through small tubes inside the heater core. Then, the heater fan blows on the tubes, sending warm air through the heating vents and into your vehicle. The heater hoses will then transfer the heated engine coolant out of the heater core and back to the engine. Heater Hoses are made of rubber and deteriorate with time. Inspection and replacement should be a part of any vehicles maintenance.

Thermostats

The average human body sits at about 98.6°F, if it’s just a few degrees higher, it suggests something is off. A car engine works much the same way, averaging between 195-220°F. One of the main components in charge of regulating how hot or cold it gets is the thermostat.

How does a car thermostat work?

Simply put, it responds to temperature changes in the engine coolant. If it is cold, the thermostat stays closed, keeping it in the engine.
If it gets too hot, the thermostat opens, allowing it to flow to the radiator where it will cool down. The Engine light and or temperature gauge in your vehicle are the best quick indicators that you may have a thermostat issue. It is best not to wait. A thermostat that is not operating properly can overheat your engine and cause permanent damage.

A/C Controls/Controller Replacement & Programming

The AC control module is the brain of the whole system. This electronically controls the interior AC functions such as fan speed, temperature, and which vents the air comes from as well as controlling the AC compressor and mechanical system. It may even take measurements of the outside and cabin air temperatures to regulate the air temperatures in the climate control system. Today’s modern vehicles can get readings from multiple locations throughout the vehicle making troubleshooting and diagnosis even more difficult. AC modules need to be programmed using special tooling and to the manufacture’s latest software updates.