This is because electric condenser fans are fixed in speed, and will not compensate for high engine RPM. 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 use a pressure temperature chart or be using diagnostic gauges. This is called short cycling. However, in this post I’ll concentrate on understanding pressure readings to diagnose car AC issues. Sometimes it's very simple. This Video explains how to troubleshoot Auto AC problems related to pressure using a Manifold Gauge Set. Blower set to HIGH speed 3. The greater the temperature, the greater the pressure. What could be wrong? Alldatadiy.com, on the other hand, uses the factory diagrams. Manifold Gauge Readings. 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. 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. Ac Troubleshooting Chart. We want nice stable conditions when testing. What my bother is doing is watching until the temperature stops dropping or starts to rise and says stop. Tachometer Display Failure Gauge pressure is the first tool in AC troubleshooting. Eautorepair.net redraws factory wiring diagrams in color and includes the component, splice and ground locations right in their diagrams. 3-ounce partial charge at 70° shows the SAME pressure as a fully charged system. The red hose attaches to the high pressure valve and the blue hose connects to the low pressure or suction valve. The table below shows 7 Gauge Readouts that you may encounter. Click on the image above and find the type of refrigerant metering device your vehicle uses. Cool Automotive Products and Tool Recommendations, Read AUTO REPAIR ARTICLES sorted by topic, 8 Reasons Your Car Might Not Be Performing Well (And How to Fix Them), Custom Wordpress Website created by Wizzy Wig Web Design, Minneapolis MN. Ah, this is the most asked question there is. That's where the manifold gauge set comes into play. This entry was posted in Auto Repair Tips, Automotive Tips, Tips on by ATC. If you don’t know which system you have, you can misinterpret the low side readings right off the bat and think your system is undercharged. If engine speed needs to be substantially increased to bring pressures in range, that's a sign that the compressor is getting weak. Usually the compressor will show the inability to generate enough suction and pressure at or near idle speeds. That indicates the quantity of refrigerant is enough that the entire coil is being used. A manifold gauge set measures refrigerant pressures inside of an air conditioning system. But gauges can give your a rough idea of whats might be going on with your system when it’s running. Honda A C Pressure Chart. A clogged orifice tube will starve a compressor of oil. A C Gauge Readings Troubleshooting Charts . Possible faults include – fuse, pressure sensor, fan belt slipping, relay, wiring break, no gas, compressor fault. Ac Gauge Readings And Meanings . 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. Connect the air indicators of the collectors. Static pressure can also be used to determine if a system has enough pressure to begin leak testing. If you want to easily check the pressure readings of your AC system, a simple way to do it is by using a pressure gauge, which you can buy for a cheap price at your local shop or from online stores like Amazon. An automotive air conditioner has a high and low side, divided by a metering device and the A/C compressor. System diagnosis ac pressure gauge readings ricks r 134a system pressure chart ac pro 2008 rabbit ac stopped working automotive air conditioning Troubleshoot Automotive Air Conditioning ProblemsAc Pressure Gauge Readings Ricks Auto Repair Advice Automotive And How ToDiagnose Car Ac With Gauges Ricks Auto Repair Advice Automotive And How ToHow To Recharge Your Car S… Notice the scale on this high side gauge reads from 0 to 500 PSI. Both the high and low side of the system have equalized. Auto A C Troubleshooting. Close the doors. Then the low side gauge will climb back up to 45 psi as the high and low side equalize. For example, you might see a low high side pressure and determine the compressor is bad, when in fact, your vehicle is equipped with a variable displacement compressor. What could be wrong? Take the Video Tour! We might determine if there is liquid refrigerant in the system, but we won't be able to tell how much liquid it contains. For this, you need a set of A/C service gauges. How to test AC pressures with a manifold gauge. or expansion valve. 4. On front wheel drive cars, never rev the engine or hold the engine at high RPM while charging or checking pressures. We should measure high and low side pressure at stable engine speeds. Any change of temperature brings with it a change of pressure. That's important, since the gauge set is used to measure pressure within the system. A C Pressure Troubleshooting Chart . 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. A defective fan clutch could cause pressures to reach dangerous levels at higher engine RPM. When the freon is low the air conditioning system will not cool as quickly or even at all. Basic Troubleshooting. If there’s NO refrigerant in the system. 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. The same holds true on rear wheel drive cars with engine driven fans. 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. Most low pressure switches require at leas 20-psi before they’ll engage the compressor clutch. Two hose will be attached to the service ports on the vehicle during service. Those that appear to be stuck closed may have inlet screens clogged with ground up desiccant particles. Bigger problem? When the pressure in the manifold gauges is around 30 psi away from the chart value, I start to let in less Freon and I wait until my brother says to stop. To understand just how an air conditioning system works, we must first understand the nature of heat. To find out what in your vehicle, click on the image to the right and find your vehicle. One thought on “ Troubleshooting Tips for Your Car’s AC Unit ” Anzael LLC August 22, 2016 at 5:06 am. The system operates in a specific range based on outside ambient temperature. That allows the high and low pressures to equalize. If the compressor is pumping against a blockage the red gauge will be too high. 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. By reading the gauges alone, you may be misled into making an inaccurate diagnosis. Each hose has its own identifying color. And it's easy to reach in and feel how cold the vent temps are getting. While checking the AC Condenser, inspect the Radiator / AC cooling fan motor(s). The basic manifold gauge set usually has three hoses. Measure temperature about 1-ft in front of the grille. This can be purchased over the counter at most auto parts stores. What’s going on? Of all the bad expansion valves seen over the years, I think those that stick closed are most common. We would like to keep engine and exhaust heat from causing abnormal heat load on the evaporator. With static pressure, you will only know if the system has some amount of liquid refrigerant present. Let's take the fixed orifice tube system for example. A faulty automotive air conditioner can be one of the more difficult issues to diagnose and repair. The next thing you should check when troubleshooting a no cooling problem is system pressure. Many sources tell you to start your charge diagnosis by checking static pressure. You can’t recover refrigerant through the gauges to get down to the factory specified fill capacity. Tech Republic. ZDNet. After compressor disengagement, the rise in suction side pressure will usually be very slow. Those are the easy ones. The air gauges consist of two gauges and three hoses, one red, one blue and one yellow. Possible faults include – blocked filter, crushed pipe, … Using Gauges for Troubleshooting. You can begin testing with only 45 psi. On hot humid days (with R12), you could say ambient temperature plus 100 PSI., and be pretty close. Windows can be open. 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. This has to be our least favorite item to diagnose. Author: Mike Thomas. For this reason we simply can't say 30 on the low side and 200 on the high side. The same applies if your system is overcharged. Click on the image to find which type of system is used on your vehicle. A. We created this FAQ to help answer some of the most common questions we receive on using a gauge set and hopefully provide some explanation on pressure readings. Technician B says if the needle moves more than .01 "hg after the evacuation process is complete, the system should be inspected for leaks. 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