Windows can be open. Connect the quick release connectors to the service ports on the high and low side refrigerant hoses. It's not producing suction, and it's not producing pressure. There are many things that can cause your car’s AC (air conditioning) to malfunction. It reads positive pressure only. At the same temperature, if the system showed only 75 psi, we could say with confidence, the system is low. Static pressure will not be used to determine if a system is fully charged. Your manifold gauge set should have a corresponding gauge and control knob for each of the two service hoses. AC System Diagnosis. Then use the chart below to find “normal” pressures for that temperature. Normal Conditions Air in cooling system (insufficient suction) What’s going on? In most cases, their diagrams are right from the factory manuals. Of all the bad expansion valves seen over the years, I think those that stick closed are most common. Any change of temperature brings with it a change of pressure. Then the low side gauge will climb back up to 45 psi as the high and low side equalize. My air conditioning was working last week, and then it quit working. The low side pressure gauge is called a compound gauge. A manifold gauge set measures refrigerant pressures inside of an air conditioning system. Gauge pressure is the first tool in AC troubleshooting. In most cases, the hose intended for the low pressure service port is blue, and the hose intended for the high pressure service port is red. ZDNet. Comments are closed. If the high and low gauges read 0, the system is empty. One thought on “ Troubleshooting Tips for Your Car’s AC Unit ” Anzael LLC August 22, 2016 at 5:06 am. With the engine running and AC on and an ambient temperature of 75°F, a typical normal reading is around 35/150, AC manifold gauges show system is low on charge, Here the gauges show lower than normal pressures on both the high and low sides. The ONLY way to know if your system is properly charged is to evacuate it and add new refrigerant with a scale. Suggestions. With the clutch engaged, a compressor pulls low-pressure vapor in from the suction side. Ac Troubleshooting Chart. This can be done at engine speeds just slightly above idle. Who is correct? Let’s look as some examples to see how static pressure can fool you. Auto AC Troubleshooting Guide | All Car Specialists Air Conditioning Troubleshooting and Repair Troubleshooting chart for vehicle air conditioning systems Troubleshooting | AutoZone.com How to Troubleshoot & Fix an Air Page 3/28. Just because cold air isn't coming from the vent doesn't mean the system isn't working. With our initial pressure reading, we can tell if the system has enough pressure to satisfy the low pressure switch and enable the compressor to operate. On front wheel drive cars, never rev the engine or hold the engine at high RPM while charging or checking pressures. Though I might add, that's about where you'll usually end up. What is this so important? Using Gauges for Troubleshooting. If the system has a TXV or H block, you will not be able to charge by feeling the evaporator outlet tube like we can on a FOT system. As a prerequisite, anyone interested in learning how to use a gauge set should first take a few moments to learn how the refrigeration cycle works and understand how refrigerant flows through the system. When the compressor kicks in, the suction against the restricted orifice will cause the compressor to quickly cycle out. Contaminant particles from the AC Compressor or AC Accumulator/Drier restricting the flow of refrigerant can lead to poor cooling. For this reason we simply can't say 30 on the low side and 200 on the high side. At this point, he compressor will kick back on and the cycle will repeat itself. Both the high and low side of the system have equalized. This Video explains how to troubleshoot Auto AC problems related to pressure using a Manifold Gauge Set. We could add or remove refrigerant and still nothing would happen. This in itself will help you immensely when it comes time to identify the high and low side of the system. They include wiring diagrams and technical service bulletins. Ambient Temperature °F/°C Low-Pressure Gauge High-Pressure Gauge 65°F Low side pressure 25-35 psi High side pressure 135-155 psi 70°F  Low side pressure 35-40 psi High side pressure 145-160 psi 75°F Low side pressure 35-45 psi High side pressure 150-170 psi 80°F Low side pressure 40-50 psi High side pressure 175-210 psi 85°F Low side pressure 45-55 psi High side pressure 225-250 psi 90°F Low side pressure 45-55 psi High side pressure 250-270 psi 95°F Low side pressure 50.55 psi High side pressure 275.300 psi 100°F Low side pressure 50-55 psi High side pressure 315-325 psi 105°F Low side pressure 50-55 psi High side pressure 330-335 psi 110°F Low side pressure 50.55 psi High side pressure 340.345 psi Ambient temp is the outside atmospheric temperature. Each refrigerant has it's own static pressure at every corresponding degree in temperature. This is because electric condenser fans are fixed in speed, and will not compensate for high engine RPM. Ah, this is the most asked question there is. If you’re tracking down a wiring issue, Eautorepair.net is the better choice. You need to consider the chance of a blend door problem. Let’s get this straight from the get-go, gauges can tell you if the system pressures are in a normal range, over-pressurized, or under-pressurized, but they CANNOT tell you if the system has the correct charge. When the freon is low the air conditioning system will not cool as quickly or even at all. Let's assume that only half the evaporator is full of boiling, heat removing, liquid refrigerant. An automotive air conditioner has a high and low side, divided by a metering device and the A/C compressor. For example: with the engine off and AC not run for at least an hour, a 70° your readings should be 35-40 psi on the blue gauge and around 145-160. It can really save you in emergency situations. Latest News from. What do you think is wrong? We like to test with the system in MAX position on high blower with doors closed. Kozyvacu AUTO AC Repair Complete Tool Kit with 1-Stage 4.5 CFM Vacuum Pump, Manifold Gauge Set, Hoses and its Acccessories … (KZTA35011) (KZTA35011) 4.4 out of 5 stars 1,197 I added some refrigerant to my car, and it still won't get cold. The system is close to being full, but that  discharge air is only slightly cool. The ONLY way to know if your system is properly charged is … Ambient Temperature °F/°C Low-Pressure Gauge High-Pressure Gauge 60°F Low side pressure 7-15 psi High side pressure 120-170 psi 70°F  Low side pressure 7-15 psi High side pressure 150-250 psi 75°F Low side pressure 35-45 psi High side pressure 150-170 psi 80°F Low side pressure 40-50 psi High side pressure 175-210 psi 85°F Low side pressure 45-55 psi High side pressure 225-250 psi 90°F Low side pressure 45-55 psi High side pressure 250-270 psi 95°F Low side pressure 50.55 psi High side pressure 275.300 psi 100°F Low side pressure 50-55 psi High side pressure 315-325 psi 105°F Low side pressure 50-55 psi High side pressure 330-335 psi 110°F Low side pressure 50.55 psi High side pressure 340.345 ps, Unscrew the protective port caps and store in a safe place. • You must know the type of compressor in your vehicle. The red hose attaches to the high pressure valve and the blue hose connects to the low pressure or suction valve. Click on the image to find which type of system is used on your vehicle. To find out what in your vehicle, click on the image to the right and find your vehicle. However, Alldatadiy.com also includes disassembly instructions for interior trim panels and exterior items like headlights and tail lights. We would like to keep engine and exhaust heat from causing abnormal heat load on the evaporator. A/C System Troubleshooting (Pg 1) HFC 134a A/C TROUBLE SHOOTING I (REFRIGERATION CIRCUIT ... For Insufficient Cooling . A C Gauge Readings Troubleshooting Charts . This will look like beach sand packed into the inlet. Alldatadiy.com, on the other hand, uses the factory diagrams. If the low side lines are obviously cold, and pressures are within range, we should think about looking inside the vehicle for the problem. Blower set to HIGH speed 3. A clogged orifice tube will starve a compressor of oil. You can begin testing with only 45 psi. The AC evaporator acts like a huge ice cube with holes in it. The working pressure of this gauge is from 0 to 120 PSI. To understand just how an air conditioning system works, we must first understand the nature of heat. And it's easy to reach in and feel how cold the vent temps are getting. As soon as the compressor engages, it will cycle off rather quickly when the suction side of the compressor draws the pressure on the low side below 20 psi.. You will see the low side gauge at 45 psi, drop quickly to 20 psi, at which point the compressor will cycle off. Using the chart below, if the R-134a system has a static pressure of 88 psi at 80 degrees F., we can then assume the system has some amount of liquid refrigerant.