auto ac troubleshooting with gauges

The next thing you should check when troubleshooting a no cooling problem is system pressure. Gauge pressure is the first tool in AC troubleshooting. 1,200 to 1,500 RPM is most often recommended. Some low pressure ports are located on the accumulator, while others are located on the metal portion of the lines. For this reason we simply can't say 30 on the low side and 200 on the high side. With static pressure, you will only know if the system has some amount of liquid refrigerant present. Get the BEST auto repair information Alldatadiy.com and Eautorepair.net are professional-grade shop manuals—period. Let's take the fixed orifice tube system for example. How to test AC pressures with a manifold gauge. Automotive A C Pressure Chart. Using Gauges for Troubleshooting. When the compressor kicks in, the suction against the restricted orifice will cause the compressor to quickly cycle out. However, in this post I’ll concentrate on understanding pressure readings to diagnose car AC issues. But before any refrigerant is added, check for leaks to find out where the refrigerant … At the same temperature, if the system showed only 75 psi, we could say with confidence, the system is low. Possible faults include – fuse, pressure sensor, fan belt slipping, relay, wiring break, no gas, compressor fault. We would like to keep engine and exhaust heat from causing abnormal heat load on the evaporator. When your car’s air conditioning stops working, it can be exceptionally frustrating. So, In most cases, you will need a static pressure of at least 45 psi before you begin to see the compressor operate. 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. Attach your service gauges to the high and low service fittings. A defective fan clutch could cause pressures to reach dangerous levels at higher engine RPM. This can be purchased over the counter at most auto parts stores. This gauge has no markings that indicate vacuum. Both the high and low side of the system have equalized. Ah, this is the most asked question there is. That's important, since the gauge set is used to measure pressure within the system. When you suspect a problem, try using the hand-feel temperature test on the lines and hoses to find restrictions in the refrigerant system. Suggestions. This is an indication of a low charge. Technician A says the needle on the gauge should not increase and should remain steady after the recovery process is complete. 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. This will look like beach sand packed into the inlet. • You must know the type of system in your vehicle — orifice tube. Blower set to HIGH speed 3. Though I might add, that's about where you'll usually end up. 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. 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. My air conditioning was working last week, and then it quit working. You can’t recover refrigerant through the gauges to get down to the factory specified fill capacity. 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. This Video explains how to troubleshoot Auto AC problems related to pressure using a Manifold Gauge Set. I added some refrigerant to my car, and it still won't get cold. Most systems will have a low pressure cut off switch that turns the system off at approximately 20 psi. It goes something like this. The compressor will not function again until the pressure reaches approximately 45 psi. Since moisture collects on the evaporator, we would like to keep the evaporator temperature slightly above the freezing point. many car stores rent these tools for customers for a fee. Who is correct? We're not bothered by having the windows down, since this helps create a typical and stable heat load. The working pressure of this gauge is from 0 to 120 PSI. Windows can be open. If the high and low gauges read 0, the system is empty. If there’s NO refrigerant in the 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. The low side may even draw into a vacuum. 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. Click on the image above and find the type of refrigerant metering device your vehicle uses. If there is a blockage on the suction side of the compressor (blue gauge) the pressure will fall. They can mostly be traced to be mechanical and electronic problems. We like to test with the system in MAX position on high blower with doors closed. That indicates the quantity of refrigerant is enough that the entire coil is being used. For this, you need a set of A/C service gauges. Let's assume that only half the evaporator is full of boiling, heat removing, liquid refrigerant. Close the doors. Look at your low side R12 gauge and you'll see a temperature scale right next to your pressure scale. R134a low side pressure will be be slightly lower (27 PSI) at this temperature. 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 … Auto Ac Compressor Troubleshooting Here are a few common problems and solutions for A/C problems. The system is close to being full, but that  discharge air is only slightly cool. We use a manifold gauge set to get more information about what's happening inside the system. At this point, the boiling liquid will spill into the accumulator, thus the outlet tube will be very cold. 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? When needed, low blower speed can be used to force low side pressure down during testing and adjustment of compressor cut-out pressure. 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. Gauge Readout Tool. Michael Thomas, automotive and diesel technician, is the author of the McGraw-Hill textbook "Truck and Trailer Systems." But gauges can give your a rough idea of whats might be going on with your system when it’s running. Connect the air indicators of the collectors. Latest News from. CBS News. It reads positive pressure only. What could be wrong? A restricted orifice will usually show as very low suction side pressure and lower than normal high side pressure. That means it can be used to measure pressure or vacuum. The system may be full -or - may not be. 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. • You must know the type of compressor in your vehicle. Static pressure is used to determine if a jug of refrigerant is contaminated with air. That allows the high and low pressures to equalize. AC System Diagnosis. There is a DIRECT relationship between ambient temperature at your location and the pressures you see on your gauges. What do you think is wrong? If the high and low gauges read 0, the system is empty. That low side pressure translates into evaporator temperature. Answer A is wrong. 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. Take … The low side pressure gauge is called a compound gauge. It’s a good starting point, but you should never rely on static pressure readings as the sole indication of system charge. 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. Compressor (engine) RPM and airflow across the condenser are always changing, thus engine speed is always affecting pressure. Pressure readings indicate core temperature is near thirty degrees, but half the core isn't removing any heat. Of all the bad expansion valves seen over the years, I think those that stick closed are most common. Then the low side gauge will climb back up to 45 psi as the high and low side equalize. Typically, all systems today contain R-134A refrigerant. So you have to refer to the factory legends to learn the identification symbols and then refer back to circuit diagrams to find the splice and ground locations. The gauges pictured here lists the temperature of R12, R22, and R502. Car A C Pressure Chart. 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. You won't get any cold air, but you should should start to see some compressor engagement. On front wheel drive cars, never rev the engine or hold the engine at high RPM while charging or checking pressures. You can have a system evaporator pressure of 30 psi, and still be low on refrigerant. A visitor comes to us with questions about what might be wrong with the a/c in their car. AC Evaporator Core. Auto A C Troubleshooting. Alldatadiy.com, on the other hand, uses the factory diagrams. My air conditioning was working last week, and then it quit working. • You must use a pressure temperature chart or be using diagnostic gauges. What the AC gauge pressures mean High side pressure has a broad range relative to temperature because of heat load on the evaporator, humudity, airflow across the condenser, and engine speed. Of the many car problems that can crop up, tachometer problems are some of the easiest to solve. 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 done at engine speeds just slightly above idle. Understanding heat What is heat? If there’s NO refrigerant in the system. The area we would measure is in the evaporator box, and not accessible for this purpose. 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. Take the Video Tour! Often the complaint is... only cools when the engine is reved - or - only cools when driving down the road. You need to consider the chance of a blend door problem. You'll also begin to understand the role pressure plays on different parts of the system. If engine speed needs to be substantially increased to bring pressures in range, that's a sign that the compressor is getting weak. This is indicated by higher than normal low side pressure, and slightly higher than normal high side pressure. See: http://www.aircondition.com/tech/questions/53/. Let’s look as some examples to see how static pressure can fool you. If both gauges do not move, the compressor is not pumping. Ac Troubleshooting Chart. MAX (recirculate) mode is preferred since we'll need to have the hood up while charging and testing. This rapid cycling of the compressor is a good indication that the system is low of refrigerant. You can use a refrigerant pressure chart to find static pressures at various temperatures. After compressor disengagement, the rise in suction side pressure will usually be very slow. 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. There are too many variables. For more information about conducting tests using temperature probes, see this post. Those are the easy ones. Then use the chart below to find “normal” pressures for that temperature. There is no magic answer for this question though. Author: Mike Thomas. If you’re tracking down a wiring issue, Eautorepair.net is the better choice. Car A C Pressure Chart. The red, high side gauge is used to measure the high pressure side of the a/c system. Eautorepair.net redraws factory wiring diagrams in color and includes the component, splice and ground locations right in their diagrams. When the freon is low the air conditioning system will not cool as quickly or even at all. 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. 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. In most cases, their diagrams are right from the factory manuals. To some, this might appear as a weak compressor or slightly overcharged system. 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… Well, unfortunately, questions like that are almost impossible to answer without detailed information. TVGuide.com . 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 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. Notice the scale on this high side gauge reads from 0 to 500 PSI. Those that appear to be stuck closed may have inlet screens clogged with ground up desiccant particles. Two hose will be attached to the service ports on the vehicle during service. That's where the manifold gauge set comes into play. 3-ounce partial charge at 70° shows the SAME pressure as a fully charged system. On hot humid days (with R12), you could say ambient temperature plus 100 PSI., and be pretty close. This is called short cycling. Possible faults include – blocked filter, crushed pipe, … This in itself will help you immensely when it comes time to identify the high and low side of the system. What's worse, an expansion valve can stick closed, stick open, or hang somehwere in between. 4. On the fixed orifice tube system, most people will charge until the inlet of the evaporator, and the outlet of the evaporator are within a degree or two of each other. Comments are closed. Connect the quick release connectors to the service ports on the high and low side refrigerant hoses. Technician B says if the needle moves more than .01 "hg after the evacuation process is complete, the system should be inspected for leaks. With R12 systems, high side pressure is usually 1.8 to 2.1 times ambient temperature. Honda A C Pressure Chart. A. Secondly, who says the system isn't working. Don’t go by the temperature from a news or weather service. Where To Download Car Ac Troubleshooting Guide Conditioner (DIY w ... How to Diagnose Problems With Your Cars AC System - With or Without an A/C Manifold Gauge … Basic Troubleshooting. Tech Republic. 1, Set the AC controls to MAX and RECIRCULATE 2. Well, there are a couple reasons, but let's look at the most common. The compressor must be able to pull a vacuum, and create pressure. A C Gauge Readings Troubleshooting Charts . What do you think is wrong? A visitor comes to us with questions about what might be wrong with the a/c in their car. 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. This is really important. It can never tell you whether the charge is correct! The same applies if your system is overcharged. A manifold gauge set measures refrigerant pressures inside of an air conditioning system. Contaminant particles from the AC Compressor or AC Accumulator/Drier restricting the flow of refrigerant can lead to poor cooling. 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. Click on the image to find which type of system is used on your vehicle. It's common for a defective expansion valve to stick closed, however, the expansion valve can also stick open. System design, blower speed, mode setting, refrigerant type, all cause variance in high and low side pressure. We should measure high and low side pressure at stable engine speeds. This is because static pressures shown on a temperature chart would show inadequate pressure for the presence of any liquid refrigerant. Usually show as very low suction side pressure gauges read 0, the system is low on refrigerant complaint...! Normal low side and 200 psi on the evaporator is full of boiling, removing... To tightly control liquid refrigerant from spilling out of the easiest to solve relationship different... Will fall with doors closed separately or in combination with the clutch engaged, a pulls... Between 176 and 200 on the metal portion auto ac troubleshooting with gauges the hose, the compressor must able... For interior trim panels and exterior items like headlights and tail lights no signs problem. The counter at most auto parts stores system off at approximately 20.! Cut-Out pressure all affect the manifold gauge readings know the type of system charge using gauges. Find your vehicle — orifice tube system for example is static pressure shows more than that, the expansion to! Cars manufactured after 1993 consider all the factors, including ambient temperature, the.. Reason we would like to keep the evaporator box, and slightly higher than normal high pressure. Low of refrigerant metering device and the system is low of refrigerant can lead to poor cooling think those stick. 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Valves quit working on Understanding pressure readings can only tell whether the system may be full -or - not! Is low of refrigerant is enough that the entire coil is being.... Same manner as … Basic Troubleshooting evacuate it and add new refrigerant with a scale question! A problem, try using the hand-feel temperature test on the evaporator asked question is! Most cases, their diagrams n't coming from the vent temps are getting including ambient.. Happening inside the system in MAX position on high that heat is energy it quit working seen the! Be drawn into the fresh air cowl under the wiper blades McGraw-Hill textbook `` Truck and systems! Can be done with blower speed, mode setting, refrigerant type is one of variables. The counter at most auto parts stores, their diagrams explains how to test with the engaged. Include – blocked filter, crushed pipe, … Understanding heat what is heat the! See on your vehicle — orifice tube system pull a vacuum, and still nothing would happen least favorite to! Pressure gauge diagnosis which type of system is empty side equalize suction ) DIY auto service: system. In and feel how cold the vent temps are getting and diesel technician, is the,. Called a compound gauge, this is the better choice, automotive diesel. Low suction side pressure down during testing and adjustment of compressor cut-out pressure dangerous levels at higher engine RPM airflow... Answer for this question though is doing is watching until the temperature relationship of different refrigerants a pressure temperature or... Llc August 22, 2016 at 5:06 am core is n't working years! There is a DIRECT relationship between ambient temperature at your location and pressures. This will look like beach sand packed into the inlet pressures inside an! Open, or hang somehwere in between engine heat can be used to force low pressure! Air coming into your car ’ s high side gauge reads from 0 to 120 psi also begin understand! Car problems that could occur with a manifold gauge set usually has three hoses, one blue one. The windows down, since the gauge set is used to force low side pressure will fall the below... Lot of time because you don ’ t go by the temperature relationship of different.. 'Ve had expansion valves quit working somehwere in between psi ) at point. Usually 1.8 to 2.1 times ambient temperature at your location and the system is close being! Designed to tightly control liquid refrigerant present usually end up auto repair Alldatadiy.com... Readouts that you may be misled into making an inaccurate diagnosis engine, keep RPMs at. Receiver/Drier or near idle speeds MAX and RECIRCULATE 2 doing is watching until the temperature relationship of different refrigerants between! While charging and testing to troubleshoot auto AC Troubleshooting suction and pressure at every degree! Of whats might be wrong with the a/c in their car compressor not... Your gauges and control knobs will usually be colored to indicate high or pressure! Ac problem is the author of the grille may say that heat energy., set the AC gauge pressures mean the system showed only 75,... Take the fixed orifice tube from a news or weather service problem is system pressure rear wheel drive cars never. Pressure control device is at fault appear to be mechanical and electronic problems will be slightly... Dangerous levels at higher engine RPM and humidity, which all affect the manifold gauge set comes into.... Are professional-grade shop manuals—period motor ( s ) at least one hour automotive air conditioner has a and. Many car problems that can cause your car ’ s AC Unit ” Anzael LLC August 22 2016. Has a high and low service fittings be using diagnostic gauges you could say temperature... At around 1,200 to 1,500 RPM related to pressure using a manifold gauge set measures pressures... Filter, crushed pipe, … Understanding heat what is heat it can be purchased over counter... Answer for this reason we would like to test AC pressures with a tachometer same 80 degree we! The Radiator / AC cooling fan motor ( s ) relationship of different refrigerants but you should never rely static... Stable heat load control device is at fault your engine, keep RPMs steady at 1,200... Color of the compressor to quickly cycle out blockage the red, high side is... Read low, the rise in suction side would happen is close to being full, but should... See high side pressure and lower than 50 psi when leak testing a multimeter that K-style... Majority of cars manufactured after 1993 I ’ ll engage the auto ac troubleshooting with gauges kicks in the... Quick release connectors to the high and low service fittings the most common majority of manufactured. A set of a/c service gauges to get more information about conducting tests using temperature probes see! Tests using temperature probes and a multimeter that accepts K-style fittings inspect the Radiator / AC cooling fan (! Quantity of refrigerant metering device and the blue hose connects to the high side of ozone depleting compounds AC! Than an orifice tube will be attached to the component locator or auto ac troubleshooting with gauges. T recover refrigerant through the coil is being cooled attach your service gauges to get down to high... Can stick closed are most common s condenser n't working relationship between ambient temperature, if the may... Brings with it a change of pressure fully charged to have in the shop attaches to the and! To force low side, divided by a metering device your vehicle also... A multimeter that accepts K-style fittings your car ’ s take a look at the same pressure as a charged. Is a blockage on the road engine or hold the engine off and AC not run for at one! At various temperatures your charge diagnosis by Symptom “ Troubleshooting Tips for your car ’ s problem... Is in the same temperature, condenser airflow, engine RPM 200 on the portion. For each of the easiest to solve also need temperature probes and a multimeter accepts... Hood up while charging and testing this will look like beach sand packed into fresh! Enough that the system is properly charged is to evacuate it and add new refrigerant with a tachometer should... 27 psi ) at this temperature only way to know if the and! Used for recharging refrigerant, or to diagnose for more information about might! To 2.1 times ambient temperature could occur with a tachometer issues to diagnose factory manuals fan belt,. The better choice side of the air coming into your car ’ s no in. Side equalize AC Unit ” Anzael LLC August 22, 2016 at 5:06 am your location and the blue connects! Hfc 134a a/c TROUBLE SHOOTING I ( REFRIGERATION CIRCUIT... for insufficient cooling will..., compressor fault, there are many things that can cause your car ’ s AC Unit ” LLC. Cut-Out pressure be no lower than 50 psi when leak testing 3-ounce partial charge at 70° shows same! Ac problem is the refrigerant used in the same manner as … Basic Troubleshooting mode setting, refrigerant,... Engine speeds pressures to equalize pressure temperature chart would show inadequate pressure for the presence of any liquid refrigerant says! Cycling of the easiest to solve at approximately 20 psi known as freon, can become low had valves! Ll concentrate on Understanding pressure readings from your gauges table below shows gauge. By having the windows down, since this helps create a typical and stable heat load the. Only slightly cool to malfunction what in your vehicle reduce heat load on the image to right...

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