Static pressure will not be used to determine if a system is fully charged. If we hook the gauges up and see 80 psi on the low side, and 80 psi on the high side, and the compressor hub is spinning, it's likely that compressor is done. Latest News from. Click on the image above and find the type of refrigerant metering device your vehicle uses. Take … Troubleshooting with Gauges FAQ. Comments are closed. Then use the chart below to find “normal” pressures for that temperature. Consider all the factors, including ambient temperature, condenser airflow, engine rpm and humidity, which all affect the manifold gauge readings. Possible faults include – blocked filter, crushed pipe, … Contaminant particles from the AC Compressor or AC Accumulator/Drier restricting the flow of refrigerant can lead to poor cooling. Gauges will show very low suction side pressure along with lower than normal high side pressure. If the high and low gauges read 0, the system is empty. That allows the high and low pressures to equalize. or expansion valve. The TXV is very efficient and is designed to tightly control liquid refrigerant from spilling out of the evaporator. The AC evaporator acts like a huge ice cube with holes in it. Here I explain some simple troubleshooting techniques. Let’s take a look at some scenarios. The red, high side gauge is used to measure the high pressure side of the a/c system. What’s going on? If the low side lines are obviously cold, and pressures are within range, we should think about looking inside the vehicle for the problem. What my bother is doing is watching until the temperature stops dropping or starts to rise and says stop. The area we would measure is in the evaporator box, and not accessible for this purpose. Bigger problem? Car A C Pressure Chart. We use a manifold gauge set to get more information about what's happening inside the system. It goes something like this. This entry was posted in Auto Repair Tips, Automotive Tips, Tips on by ATC. Gamespot. Because expansion valve systems usually show show a lower suction side pressure than an orifice tube system. 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. There are many things that can cause your car’s AC (air conditioning) to malfunction. A manifold gauge set measures refrigerant pressures inside of an air conditioning system. At this point, the boiling liquid will spill into the accumulator, thus the outlet tube will be very cold. When needed, low blower speed can be used to force low side pressure down during testing and adjustment of compressor cut-out pressure. Click on the image to find which type of system is used on your vehicle. We could add or remove refrigerant and still nothing would happen. To some, this might appear as a weak compressor or slightly overcharged system. Regardless of which refrigerant is being used, the scale designated as PSI is the one used to read system pressures when charging and diagnosing an a/c system. The working pressure of this gauge is also much higher than the low side gauge. 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… Ac Troubleshooting Chart. Check the AC pressure with a pressure gauge. Tech Republic. 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. Windows can be open. The working pressure of this gauge is from 0 to 120 PSI. Those that appear to be stuck closed may have inlet screens clogged with ground up desiccant particles. What could be wrong? 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. At 70°F the 3-ounces have boiled and turned into a gas, generating the same amount of pressure as a fully charged system at the same temperature. If you’re tracking down a wiring issue, Eautorepair.net is the better choice. Auto A C Troubleshooting. For this, you need a set of A/C service gauges. Normal Conditions Air in cooling system (insufficient suction) Refer to this chart for AC pressure gauge diagnosis. 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. High pressure ports can be located on the receiver/drier or near the condenser. Car Ac Gauge Reading Chart . The basic manifold gauge set usually has three hoses. ZDNet. Connect the air indicators of the collectors. Over time the refrigerant, also known as freon, can become low. It can never tell you whether the charge is correct! If your static pressure shows more than that, the compressor clutch should engage. TVGuide.com . While checking the AC Condenser, inspect the Radiator / AC cooling fan motor(s). Get the BEST auto repair information Alldatadiy.com and Eautorepair.net are professional-grade shop manuals—period. The important thing to keep in mind is static pressure changes based on temperature. My air conditioning was working last week, and then it quit working. In most cases, their diagrams are right from the factory manuals. The compressor must be able to pull a vacuum, and create pressure. This is indicated by higher than normal low side pressure, and slightly higher than normal high side pressure. Basic Troubleshooting. My air conditioning was working last week, and then it quit working. What the AC gauges can tell you. Most systems will have a low pressure cut off switch that turns the system off at approximately 20 psi. Then the low side gauge will climb back up to 45 psi as the high and low side equalize. Your manifold gauge set should have a corresponding gauge and control knob for each of the two service hoses. Attach your service gauges to the high and low service fittings. 1, Set the AC controls to MAX and RECIRCULATE 2. An automotive air conditioner has a high and low side, divided by a metering device and the A/C compressor. If both the high and low side pressure gauges read low, the system is low on refrigerant and the system needs recharging. It's common for a defective expansion valve to stick closed, however, the expansion valve can also stick open. You won't get any cold air, but you should should start to see some compressor engagement. Ac Gauge Readings And Meanings . Suggestions. R134a Pressure Gauge Chart This chart details how ambient temperature correlates with the system refrigerant charge pressure, and how it affects high and low side psi readings. You need to consider the chance of a blend door problem. And it's easy to reach in and feel how cold the vent temps are getting. A C Pressure Troubleshooting Chart . With R12 systems, high side pressure is usually 1.8 to 2.1 times ambient temperature. 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. The system operates in a specific range based on outside ambient temperature. Honda A C Pressure Chart. You can begin testing with only 45 psi. Automotive Ac Troubleshooting With Gauges. Connect the quick release connectors to the service ports on the high and low side refrigerant hoses. The red hose attaches to the high pressure valve and the blue hose connects to the low pressure or suction valve. What could be wrong? I added some refrigerant to my car, and it still won't get cold. You can’t recover refrigerant through the gauges to get down to the factory specified fill capacity. The gauges pictured here lists the temperature of R12, R22, and R502. The low side pressure gauge is called a compound gauge. The reason 30 psi on the low side is just about right is because that translates into an evaporator temperature somewhere around the freezing point of water. This can be purchased over the counter at most auto parts stores. This Video explains how to troubleshoot Auto AC problems related to pressure using a Manifold Gauge Set. 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. Both the high and low side of the system have equalized. This in itself will help you immensely when it comes time to identify the high and low side of the system. CNET. You can have a system evaporator pressure of 30 psi, and still be low on refrigerant. 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. Automotive A C Pressure Chart. See the pressure chart below to see what I mean. What do you think is wrong? On hot humid days (with R12), you could say ambient temperature plus 100 PSI., and be pretty close. The same holds true on rear wheel drive cars with engine driven fans. Well, R-134a boils at -15.34°F. The smaller scales near the middle of the gauge list the temperature relationship of different refrigerants. You’ll need manifold gauge set if you want to properly diagnose your car AC with gauges. No. Any change of temperature brings with it a change of pressure. Typically, all systems today contain R-134A refrigerant. But gauges can give your a rough idea of whats might be going on with your system when it’s running. 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. In other words, if your system is low on charge, you can’t use your gauge set to add refrigerant to get to factory specified fill capacity. How to test AC pressures with a manifold gauge. When you suspect a problem, try using the hand-feel temperature test on the lines and hoses to find restrictions in the refrigerant system. R-134a is the refrigerant used in the majority of cars manufactured after 1993. But static pressure readings can only tell whether the system is completely empty or has some refrigerant in it. Measure temperature about 1-ft in front of the grille. 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 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. On that same 80 degree day we would see between 176 and 200 PSI on the high side of an R134a system. To understand just how an air conditioning system works, we must first understand the nature of heat. It’s a good starting point, but you should never rely on static pressure readings as the sole indication of system charge. I added some refrigerant to my car, and it still won't get cold. We should measure high and low side pressure at stable engine speeds. After compressor disengagement, the rise in suction side pressure will usually be very slow. We like to test with the system in MAX position on high blower with doors closed. Alldatadiy.com, on the other hand, uses the factory diagrams. 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. Your static pressure should be no lower than 50 psi when leak testing. With the clutch engaged, a compressor pulls low-pressure vapor in from the suction side. CBS News. The low side may even draw into a vacuum. It's not producing suction, and it's not producing pressure. Possible faults include – fuse, pressure sensor, fan belt slipping, relay, wiring break, no gas, compressor fault. 3-ounce partial charge at 70° shows the SAME pressure as a fully charged system. That's where the manifold gauge set comes into play. If you need to dig into your doors, dash or console, Alldatadiy.com is the better choice because Eautorepair.net doesn’t any interior or exterior trim or body part removal. This condition has a few possible causes: the AC system could be low on refrigerant, an electrical problem … • You must know the type of compressor in your vehicle. This will look like beach sand packed into the inlet. Technician A; B. That's important, since the gauge set is used to measure pressure within the system. If the compressor is pumping against a blockage the red gauge will be too high. 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. System design, blower speed, mode setting, refrigerant type, all cause variance in high and low side pressure. A visitor comes to us with questions about what might be wrong with the a/c in their car. A faulty automotive air conditioner can be one of the more difficult issues to diagnose and repair. When the compressor kicks in, the suction against the restricted orifice will cause the compressor to quickly cycle out. Let's assume that only half the evaporator is full of boiling, heat removing, liquid refrigerant. Notice the scale on this high side gauge reads from 0 to 500 PSI. Pricing: ---Eautorepair.net--- 1 month subscription $19.95 per vehicle 1-year subscription $29.95 per vehicle 4-year subscription $44.95 per vehicle ---Alldatadiy.com--- 1-year $29.95 subscription: additional vehicles $19/95 each 5-year $49.95 subscription: additional vehicles $34.95 each Which one should YOU choose? The ONLY way to know if your system is properly charged is … The numbers around the outside of this gauge indicate pressure in pounds per square inch (PSIG), and the numbers near the bottom indicate vacuum in inches of mercury. A. For example, a thirty pound can of refrigerant will show the same pressure whether it has thirty pounds in it or if it only has 1 ounce. A/C System Troubleshooting (Pg 1) HFC 134a A/C TROUBLE SHOOTING I (REFRIGERATION CIRCUIT ... For Insufficient Cooling . A restricted orifice will usually show as very low suction side pressure and lower than normal high side pressure. AC System Diagnosis. Usually the compressor will show the inability to generate enough suction and pressure at or near idle speeds. DIY Auto Service: AC System Diagnosis by Symptom. If the high and low gauges read 0, the system is empty. If there’s NO refrigerant in the system. The next thing you should check when troubleshooting a no cooling problem is system pressure. Troubleshooting Car Ac With Gauges. Two hose will be attached to the service ports on the vehicle during service. By reading the gauges alone, you may be misled into making an inaccurate diagnosis. • You must use a pressure temperature chart or be using diagnostic gauges. All Car wants to offer you some tips and guidance to help you and us determine what is wrong before you bring in your car. Well, there are a couple reasons, but let's look at the most common. Of the many car problems that can crop up, tachometer problems are some of the easiest to solve. Ac Manifold Gauge Readings . 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. At this point, he compressor will kick back on and the cycle will repeat itself. Static pressure is used to determine if a jug of refrigerant is contaminated with air. This is an indication of a low charge. If there’s NO refrigerant in the system. Of all the bad expansion valves seen over the years, I think those that stick closed are most common. The system is close to being full, but that  discharge air is only slightly cool. A visitor comes to us with questions about what might be wrong with the a/c in their car. TV.com. Again, refrigerant type is one of those variables we have to consider. There are too many variables. Same reason we would like to test with doors closed. Take the Video Tour! We would like to keep engine and exhaust heat from causing abnormal heat load on the evaporator. Low blower speed will reduce heat load on the evaporator to the point where compressor cycling can occur. Though I might add, that's about where you'll usually end up. You'll also begin to understand the role pressure plays on different parts of the system. Gauge Readout Tool. many car stores rent these tools for customers for a fee. Ah, this is the most asked question there is. What's worse, an expansion valve can stick closed, stick open, or hang somehwere in between. Ac Troubleshooting Chart. The ONLY thing a static pressure reading can tell you is if there is enough pressure in the system to satisfy the low pressure switch and allow the compressor clutch to engage. That yellow hose will be attached to the refrigerant cylinder while charging or the vacuum pump when the system is being evacuated of air and moisture. Like the color of the hose, the gauges and control knobs will usually be colored to indicate high or low pressure. The greater the temperature, the greater the pressure. One thought on “ Troubleshooting Tips for Your Car’s AC Unit ” Anzael LLC August 22, 2016 at 5:06 am. We want nice stable conditions when testing. Rapid compressor disengagement and slow engagement may indicate a clogged orifice. That means on an 80 degree day, with moderate humidity, we would expect to see between 144 to 168 PSI on the high side. A first aid kit can be another good one to have in the emergency kit. Well, unfortunately, questions like that are almost impossible to answer without detailed information. This is because static pressures shown on a temperature chart would show inadequate pressure for the presence of any liquid refrigerant. The middle hose should be yellow. That indicates the quantity of refrigerant is enough that the entire coil is being used. Let’s look as some examples to see how static pressure can fool you. Car A C Pressure Chart. At the same temperature, if the system showed only 75 psi, we could say with confidence, the system is low. What the AC gauge pressures mean That low side pressure translates into evaporator temperature. We've had expansion valves quit working while on the road and show no signs of problem back in the shop. The same applies if your system is overcharged. You can’t really diagnose with just a low pressure gauge. Most low pressure switches require at leas 20-psi before they’ll engage the compressor clutch. Who is correct? Gauge pressure is the first tool in AC troubleshooting. AC Evaporator Core. 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. Some low pressure ports are located on the accumulator, while others are located on the metal portion of the lines. HVAC-02, Air Conditioning Troubleshooting and Repair Introduction Since I'm constantly receiving questions on 944 air conditioning systems, I figured it's time to come up with come helpful troubleshooting tips. However, in this post I’ll concentrate on understanding pressure readings to diagnose car AC issues. There is no magic answer for this question though. If engine speed needs to be substantially increased to bring pressures in range, that's a sign that the compressor is getting weak. For more information about conducting tests using temperature probes, see this post. Measure static pressure with the engine off and AC not run for at least one hour. This rapid cycling of the compressor is a good indication that the system is low of refrigerant. Compressor (engine) RPM and airflow across the condenser are always changing, thus engine speed is always affecting pressure. The compressor will not function again until the pressure reaches approximately 45 psi. Many sources tell you to start your charge diagnosis by checking static pressure. Answer A is wrong. I've seen cars with sweat rolling off the accumulator and low pressure line to the compressor, and the technician is under the hood scratching his head because no cold air is coming from the vents. This is because electric condenser fans are fixed in speed, and will not compensate for high engine RPM. This is called short cycling. Working on the 944 A/C system is no different than working on any other automotive A/C system. Secondly, who says the system isn't working. Often the complaint is... only cools when the engine is reved - or - only cools when driving down the road. Sometimes it's very simple. See: http://www.aircondition.com/tech/questions/53/. Those are the easy ones. Eautorepair.net redraws factory wiring diagrams in color and includes the component, splice and ground locations right in their diagrams. At higher engine RPM and airflow across the condenser are always changing, thus engine needs... Will climb back up to 45 psi as the high pressure side of hose! 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