AC Repair

Let’s look at how the air conditioning (AC) system works.

The objective of the air conditioning system is to remove the heat from inside the cab of the vehicle. The compressor pumps refrigerant throughout the AC system. This refrigerant is a gas and liquid combination that is compressed and circulated under pressure and is passed through a special valve called an expansion valve that causes the refrigerant to expand.

This expansion makes the refrigerant very cold. This cold gas makes its way via metal lines into the dash area of your vehicle to the evaporator core. This evaporator core is like a small radiator, except it has cold refrigerant circulating inside and not hot antifreeze. A small fan (the AC blower fan which you control from the control panel on the dash) sits in front of the evaporator core and blows air across this cold evaporator and then through the vents inside your vehicle.

The compressor then sucks the warmed refrigerant into the condenser located at front of the vehicle. The condenser will have an electric cooling fan mounted in front or behind it to push or pull air through it to remove the heat from the refrigerant. Some vehicles still use the old fashioned fan blade driven by the engine to pull air across the radiator and the condenser.

A few causes of low air conditioner cooling or no cooling at all at idle are:

• Lack of air flow across the condenser. Make sure the electric cooling fan motor near the condenser is coming on, or in models that are equipped with a fan blade make sure this fan is turning very fast.
• Low refrigerant levels. refrigerant level and pressure should be checked by your certified air conditioning mechanic.
• Overheating. If the engine is overheating, it can have a noticeable negative affect on the air conditioning system. Some cars have two electric cooling fans, one for the air conditioning condenser and the other for the radiator. Make sure they are both working properly. Usually at idle on a hot day with the AC on both fans will be on.

When the vehicle is traveling at freeway speeds, the compressor is pumping the refrigerant throughout the system much faster and harder than at idle. There is a dramatic increase in air flow across the condenser  and the engine is usually operating at a cooler, more efficient temperature as well, thus allowing the air conditioning system to operate efficiently. An air conditioning system that is somewhat low on refrigerant can still feel comfortable at freeway speeds due to the added air flow across the condenser which can overcome the ill effects of slightly low refrigerant. Periodic air conditioning performance checks by your mechanic are the best way to keep the system in great shape.

Cooling System Flushing – We Do It!

Well…not really this kind of flushing, but the concept is the same!

We start by attaching the hoses from the coolant flushing machine to several places in the cooling system and then use the pressure from the machine to shove out the old coolant and crud suspended in it. The flush process takes about 3 hours, including time to allow the hot engine to cool first. A cooling system flush, though, will not usually cure an immediate overheating problem due to plugging.

Most radiators today are small, made of lightweight aluminum, and crammed so tightly in the front of the car you can barely see it. The inside of the radiator is made up of a honey comb maze of tubes that sends the hot antifreeze on a long meandering journey inside the radiator.

The majority of the rust, dirt and sediment will be trapped at the bottom of the radiator, and we will not be able to remove enough of this compacted material to make any real significant difference in cooling ability of the system. A flush will, however, remove suspended sludge before it can settle and become compacted. Calcium and rust build up within the tubes are the main causes of radiator stoppages, and will likely cause over-heating. Also, the additives in the antifreeze deplete and break down with time and mileage and should be replaced with fresh coolant.

At some shops the term “flushing” the cooling system has been replaced with “draining and refilling” the cooling system. Removing the lower radiator hose or radiator drain cock to drain out the old antifreeze and replace with the new fluid is essentially “draining and refilling the cooling system.” This of course will only remove old contaminated fluid, along with any minor surface debris. If the radiator IS stopped up, removal of the radiator from the car for rodding-out and rebuilding, or replacing the radiator are really the only two viable options.

There are many “radiator flush” additives on the market, There are very few cooling system problems that can be solved by the contents of a can.
Flushing your auto radiator and installing new coolant every two to three years WILL help maintain and extend the life of your vehicle, but will probably NOT cure a major over-heating problem.