HVAC-02, Air Conditioning Troubleshooting and Repair Since I'm constantly receiving questions on 944 air conditioning systems, I figured it's time to come up with come helpful troubleshooting tips. Working on the 944 A/C system is no different than working on any other automotive A/C system. They have all the same components which function in the same manner as any other A/C system. First, if you're having a problem with the A/C system on your 944, there are two ways you can approach solving the problem. The first is to just start replacing components and hope you get lucky by replacing the faulty component the first time. The other method involves doing some actual testing to narrow down the cause of the problem. In order to properly test the A/C system and narrow down the possible causes of your problem, you're going to have to invest in a set of A/C gauges. Before we begin with the actual troubleshooting, to properly troubleshoot the A/C system, it's extremely helpful to understand how the automobile A/C cycle works.

So, we'll begin by discussing automotive air conditioning theory of operation. There are two basic types of automotive air conditioning systems. The type of system is determined by the device used to control the expansion of the high pressure, high temperature liquid to a low pressure, low temperature liquid. One system uses and expansion valve while the other uses an orifice tube. 944s use an expansion valve system. We'll discuss the operation of both. The first component in the A/C cycle is the compressor. The compressor takes low temperature refrigerant gas and compresses it into a high pressure, high temperature gas. The refrigerant is then sent to the condenser which sits in front of the radiator. The condenser removes some of the heat from the refrigerant which causes the refrigerant to change phase from a hot gas to a warm liquid. In the expansion valve A/C system, the warm liquid is then passed through a receiver-drier which removes moisture (via a desiccant in the drier) from the refrigerant to maximize the efficiency of the heat exchange capability of the refrigerant.

On 944s, the receiver-drier is a small canister (probably with a sightglass on top) located near behind the driver's side headlight (LHD cars). No phase change occurs as the refrigerant passes through the receiver-drier. From there, the refrigerant is then passed through the expansion valve. The expansion valve has a sensing line that is attached to the suction of the A/C compressor. The expansion valve senses the pressure at the suction of the A/C compressor and modulates to maintain the pressure at the compressor suction. On 944s, the expansion valve is located near in the passenger's footwell (LHD cars) near the center console next to the firewall. In the orifice tube system, the warm liquid refrigerant passes directly from the condenser to the orifice tube. The orifice tube is a fixed expansion device. The pressure drop across the orifice tube is proportional to the pressure into the orifice tube. So, the orifice tube system maintains the pressure at the suction of the A/C compressor by cycling the compressor on and off via a clutch.

This is the type of system typically used by GM vehicles. The expansion of the warm liquid through the expansion valve or orifice tube causes a pressure drop and hence a temperature drop in the refrigerant. So, out of the expansion device we get a low temperature liquid refrigerant. The next component in the A/C system is the evaporator. Air from the passenger's compartment passes across one side of the coils in the evaporator. central ac unit not runningThe low temperature liquid refrigerant passes through the other side of the coils. does ac unit use gasThe refrigerant removes heat from the air in the passenger's compartment and returns to the A/C compressor suction as a low temperature gas (phase change).small ac unit for cars In the orifice tube system, there is an accumulator located between the evaporator and the A/C compressor suction.

The accumulator has moisture removal desiccant just like the receiver-drier used in the expansion valve system. However, it also collects any un-evaporated refrigerant to prevent liquid lock of the compressor. This can occur due to the cycling action of the compressor. The diagrams below show the two different A/C system cycles. The following is an general A/C system troubleshooting guide. Realize that it is generic and many of the things listed here may not apply to the 944. The following table is a general guideline for A/C system pressures and temperatures based on ambient outside temperature. Remember that these are a guideline and your actual temperatures and pressures will vary depending on humidity in the air and the condition of your system. A/C System Pressure ReadingsHomeAbout UsShippingReturnsCheckoutLearningTroubleshooting Your Portable Air ConditionerIf your portable air conditioner isn't working properly you might want to wait before you call a repairman and pay an expensive fee to have it fixed.

Some portable AC problems can easily be repaired at home. This troubleshooting guide will help you identify what is wrong with your portable air conditioning unit and walk you through the steps to fixing it yourself.Below are some common issues with portable air conditioners. Read the list to find which one most closely matches your problem and then follow the steps in order to fix it. Please note if you are experiencing any issues that aren't listed below or that require any electrical wiring, it is strongly recommended that you don't try to fix it yourself but rather contact a professional. My Portable Air Conditioner Won't StartCheck that the water reservoir isn't full. Air conditioners act as dehumidifiers because they remove water from the air, which collects in buckets that need to be emptied periodically. If it's full, a float switch can interrupt power to the unit and halt operation. Make sure that the air conditioning unit is properly plugged into the outlet. If it has an integrated circuit interrupter then make sure it hasn't been tripped.

If so, press the reset button. If the reset button won't stay engaged then there is probably a problem with the wiring and you'll need to have a professional fix it. Also, make sure that the cord itself isn't damaged. You should check the breaker to make sure the power is being supplied to the room air conditioner. If the unit is on its own circuit and a fuse is blown or the breaker is tripped then it is probably a problem with the wiring and a professional will need to fix it.My Portable Air Conditioner Isn't Cooling ProperlyCheck that the air filter has been properly cleaned by removing the grill (it should be cleaned about every two weeks). To clean the filter, remove it from the frame and tap the filter lightly with your hands to remove any dust and dirt particles. Do the same to the carbon filter (if your unit includes one). Then thoroughly rinse the filters with warm water and a mild detergent. Let them dry completely. Make sure that there isn't any furniture or objects blocking the air intake vents on the AC unit, and that there is proper clearance around the unit.

The vents might be dirty and can be easily cleaned by light vacuuming. Make sure there isn't any ice building up on the air conditioner's coils. If so, see the "IceBuildup" section below. Make sure that the portable air conditioner is correctly sized for the room you are using it in. See "Doesn't Stop Running" below.My Portable Air Conditioner Doesn't Stop RunningYou should make sure that the portable air conditioner isn't too small for the area that you are trying to cool. You can determine what size AC unit you need by looking at the BTU (British Thermal Unit) rating. It describes cooling capacity and the higher the BTU, the stronger the portable air conditioner. To get a quick estimate of how many BTUs you need just multiply the square footage of the room by 35 to get a rough estimate. You can also refer to our Air Conditioner BTU chart to easily find the BTU you need for your room. Be sure to account for extra sunny or shady areas, additional people in a room and kitchens. You should make sure that all the doors and windows are closed in the area that you are trying to cool because you want to minimize the heat gain to your home.

Portable ACs need to operate in a "closed" environment with air that is continuously circulated in order to work properly.My Portable Air Conditioner Won't Blow AirThis most likely means that the fan motor is bad. You shouldn't try to fix this yourself. Contact a professional to have it fixed properly.My Portable Air Conditioner is LeakingMake sure that the water reservoir isn't full. In more humid climates water can collect more quickly. So how often you need to drain the water bucket depends on where you live and how much you run the portable air conditioner. Almost all units also include the option for a drain hose and this can become stopped up, preventing the water from draining properly and leaking. So this hose may need to be cleaned or it is not properly installed.My Portable Air Conditioner has Ice Build-upYou should turn the air conditioner off and run the fan on high speed. This will dry out the inside of the unit and remove any ice that has built up on the coils. After about 2 hours it should be completely dry.

When the ice has melted off and it is completely dry, check that the filter has been properly cleaned. For more detailed instructions on how to clean the unit, see the above section "Isn't Cooling Properly".My Portable Air Conditioner is Making a Rattling NoiseRemove the portable air conditioner's cabinet and reposition the fan. Then tighten the screw at the center of the fan. The noise is probably caused by the fan coming in contact with the housing or coils of the unit.After following this troubleshooting guide hopefully your portable air conditioner is running properly. If for some reason it still isn't working or you have a more complicated problem that is not listed above then you should probably contact a professional. Also, it's important to reiterate that if the issue is more complex and requires any type of electrical wiring then you should contact a professional instead of trying to fix it yourself. However, repairmen can be very expensive so you might be better off purchasing a new portable air conditioner altogether if you've had yours a while.