How Air Conditioners Work & When They Don't Work


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Are you sweating and want to fix or at least learn about air conditioning, either home or car then you are at the right place.

If your looking for AUTO air conditioning help go here.

A/C trouble shooting tips

How to read and understand A/C gauges

If you know that the problem is electrial ie. fan motor not running or everything isnt running then go here to my a/c electric page.

The main thing to remember is that all freon(refrigerants) work the same way no matter what is cooled, as in ice machines,de-humidifiers,freezers,coolers for flowers,ect.

They all have a compressor, evaporator(cold coil), condensor(hot coil), expansion valve, and some way to remove the heat such as fans,water,buried underground,ect.

They may use different refrigerants such as R-11,R-12,R-502,R-111,even ammonia

Ammonia is somewhat different and dangerous so do not attempt to service these !!!!!

"Freon" is also dangerous and you should take great care not to get any liquid freon on you as it will freeze your skin on contact, The vapors are not as dangerous though make sure your in a well ventalated area because it displaces the air in the room, meaning it collects in clouds you cannot see.

Also when freon is burned (passes through a flame) it becomes toxic, when you smell something like an ammonia & bleach type smell its been burned and do not breath it.

"Freon is also under pressure some systems it can be as high as 300 or more psi.


Central Air Conditioning

First of all check the power to each unit (condenser*outside unit) Air handler (inside unit) for power, check the breakers or fuses on the inside of the house and there should be a breaker on or near the outside unit.

Check and make sure that the fans (both) outside and inside are running

If you have a package unit. The type that are on house trailers. The unit is all contained in one box with the duct work (2 duct hookups, in and out)the blower for the inside air is inside the box so just feel if any air is blowing out the ducts and the outside fan is running....P.S.-- if the cold coil is frozen than you won't feel any air blowing from the vents but the motor will still be running--. If you want to check to see if your inside air motor is running than turn your thermostat off, then click the fan switch to ON from the auto setting if its wired correctly you will hear the fan running inside the box..

The compresser must be running, it can be hard to hear if its running but they do have a buzzy type sound.

Look for any ice on any of copper tubing, if you see ice then your a/c is frozen up (cold coil).

One thing that is important is that the air coming out of the outside unit should be very warm unless you have a high efficient unit.

w If you have a split system (unit outside & a air handler inside) then while your central air is running feel the temperature of the bigger of the two copper tubes that come out of the unit. The bigger tube should be cold like a cold soda can, and the little tube should be warmish.

Pressures on gauges...

The readings on gauges are in pressure psi. If you look at the inside of the gauge there is a pressure temprature chart printed on the gauges for r-12, r-22, r-502. High and low side. Newer gauges have different charts.

Lets look at a few examples.

R-12 on the gauge.

If the pressure on an r-12 system on the low side, while the unit is running is 35 psi.(the outer black colored chart) then look at the smaller circles for the R-12 circle. The needle pointing to 35 psi. also crosses the R-12 circle, look at the corresponding number on it to determine what temperature the coil is operating at. It will be about 38 degrees F'.

If your hi side on r-12 is at 160 psi. then look on the inner part of the gauge on the high side it will read about 120 degrees f.

Lets look at r-22 on the gauge.

If you have a low side of 68 psi. reading on your gauge then look at the inner chart for r-22 at 68 psi. it is about 38 degrees f.

If you have a high side reading at 220 psi. then on your chart the gauge will read about 110 degrees f.

The evaporator (cold coil) on any air conditioning system should never be below 32 degrees f. Why because the condensate (water) on the coil will freeze, freezing up the system.

Freezers and refrigerators keep the temperature of the evaporator (cold coil) below freezing to keep the freezer cold enough to freeze. The coil operates at about 0 degrees f. So with the coil being that cold the condensate will turn to ice which will clog up the coil with ice. This will shut down the cooling. Refrigeraters have a defrost timer that turns on the heaters and shuts off the compressor. The timer keeps the defrost on for about 30-40 minutes. The thawing ice will drain down to the water pan under the frig to evaporate.

If your system runs low on refrigerant it will freeze up because the lack of pressure means the evaporator (cold coil) will be under the 32 degree mark, thus freezing the water.

It seems weird that if you loose refrigerant you would think that the system would warm up but thats not how it works. Think about it.



Auto air conditioning works the same way as all Freon systems.

They have a compressor, condensor (hot coil), evaperator (cold coil), and fans.

Under the hood is the compressor, condensor (hot coil), a shiny can (receiver with a dryer bag inside), a bunch of black tubing, and access valves.

To see more about auto air conditioning go here...

***under construction***

Other Useful Places To Go

For information on -Fuel Injection- basics
For information on -Air Conditioner electrical wiring-

For questions or comments:

The diagram below shows the "freon" (refrigerant) flow from the compressor thru the condenser (hot coil), then thru the expansion valve into the evaporator (cold coil), then back to the compressor to start all over again.

Other A/C Jbab Sites

Lets go over what happens in the diagram above.

We will begin at the compressor. The compressor is the heart of the system. It compresses the freon. While it compresses it also pumps the freon around and around the system like your heart. The compressor has 2 tubes connected to it. One tube is the outlet from the compressor. This tube is the smaller of the two. This smaller tube connects to the inlet of the condenser.

"Condenser" is the outside coil (unit) that has a fan on it. The condenser receives the freon in a gas state from the compressor. The pressure is high and so is the freon temperature. As the compressor keeps pumping, the freon is forced to go thru the coil. As the hot freon moves thru the coil it must be cooled down so the gas will turn into "liquid". Here is where the fan comes in. The fan draws air thru the coils. This takes the heat out of the freon to allow it to turn to a "liquid"

Liquid freon (refrigerant) is the KEY to cooling. Now that the freon has traveled thru the outside condensing unit and the freon has cooled and turned from a gasous state to a liquid state the freon then leaves the condenser (hot coil).

The liquid line tube is the smaller diameter tubing of the 2 lines that are connected to the unit. Also you can tell the liquid line from the gasous line by the black insulation. The smaller tubing has no black insulation covering it.

The liquid line runs from the condenser outlet up to the air handler (inside unit). Inside the air handler is where the expansion valve or capillary tubes are. The "evaporator" cold coil is inside the air handler. The liquid line is connected to either the Xvalve or capillary tube whichever you have. These valves are like a restriction. This is the point where the low side and high side are seperated.

*High Side* The tubing from the compressor thru the condenser and up to the Xvalve (restriction) in the air handler is the high side.

Now we are at the point where the cooling takes place. ***As I stated above*** the liquid is the KEY to cooling. When the liquid freon goes thru the Xvalve it enters the "evaporator" (cold coil. The evaporator is at a lower pressure (low side).

"Low Side" The copper tubing from the Xvalve thru the evaporator and back to the compressors inlet is the low side. The compressor pulls the freon in. This suction by the compressor along with the Xvalve (restriction) is how the lower pressure is created. If there was not any restriction in the system the freon would just go around and around without any cooling. With the Xvalve in the system there will be a high and low side.

Back to the *evaporator* cold coil. As the high pressure liquid in the small tubing enters the evaporator the freon will "boil" because the evaporators pressure is much lower. Its like putting alcohol on your skin, the alcohol feels cold because it is evaporating. Thats what the freon does inside the evap.

Since the compressor is sucking in all the time it keeps the freon changing from the liquid to a gas. As freon changes its state back to a gas the freon absorbs heat. So thats where the fan comes in. While the freon is absorbing heat the fan draws the air thru the cold coil to have the heat taken out of the air that circulates in the house. The evaporator does not cool the air, the freon takes the heat out of the air.

Now that the freon has passed thru the evaporator (cold coil) and absorbed the heat, the heat needs to be removed from the freon. This is done by the compressors suction where the freon with the heat is sucked in to the compressor from the large tubing with the black insulation. The compressor compresses the gas and starts all over again.

As stated above the compressor compresses the hot gas and sends it to the condenser (hot coil) to have the outside fan take the heat out of the freon and turn it back into a liquid to start the whole process over again.

Below are a few things to remember

The compressor can only compress a gas not a liquid.

The temperature of the Freon is different through out the system.

The temperature and pressure go hand in hand inside the system, when the tubing or coil is hot then the pressure will be high.

Coming out of the compressor is high pressure, so that means the Freon and the copper tubing will be hot!!

"The High and Low Side"

The low pressure (low side) starts on the exit out of the x-valve, into the evaporator (cold coil), then to the compressor.

The high pressure side is from the outlet of the compressor through the condenser (hot coil), then to the expansion valve.

To go to my webpage on electric wiring click at Jbabs electric page for general air conditioning wiring.

o If you think your system is leaking one thing to remember is that where ever the Freon is leaking there is going to be oil leaking out the same hole, so look for any oily spots on all the tubing,coils,compressor ect.

Most of the time ac problems are electrical, like a fan motor burning out or a switch goes bad. If you think you can deal with an electrical problem then visit my Jbabs electrical a/c help page here..

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