To some, this might appear as a weak compressor or slightly overcharged system. Same reason we would like to test with doors closed. 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. But gauges can give your a rough idea of whats might be going on with your system when it’s running. Manifold Gauge Readings. How to test AC pressures with a manifold gauge. To understand just how an air conditioning system works, we must first understand the nature of heat. Those are the easy ones. 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… Honda A C Pressure 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. 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. DIY Auto Service: AC System Diagnosis by Symptom. Compressors that use a variable stroke are often misdiagnosed as being defective, when only the internal pressure control device is at fault. What do you think is wrong? Pressure readings indicate core temperature is near thirty degrees, but half the core isn't removing any heat. If there’s NO refrigerant in the system. Normal Conditions Air in cooling system (insufficient suction) This is really important. 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. Compressor (engine) RPM and airflow across the condenser are always changing, thus engine speed is always affecting pressure. Let’s look as some examples to see how static pressure can fool you. I added some refrigerant to my car, and it still won't get cold. That means on an 80 degree day, with moderate humidity, we would expect to see between 144 to 168 PSI on the high side. See the pressure chart below to see what I mean. This can be done at engine speeds just slightly above idle. This in itself will help you immensely when it comes time to identify the high and low side of the system. But before any refrigerant is added, check for leaks to find out where the refrigerant … Eautorepair.net redraws factory wiring diagrams in color and includes the component, splice and ground locations right in their diagrams. Tech Republic. Windows can be open. This condition has a few possible causes: the AC system could be low on refrigerant, an electrical problem … The typical complaint for an AC problem is the AC blows warm air. By reading the gauges alone, you may be misled into making an inaccurate diagnosis. 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. 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 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. With R12 systems, high side pressure is usually 1.8 to 2.1 times ambient temperature. If there is a blockage on the suction side of the compressor (blue gauge) the pressure will fall. A defective fan clutch could cause pressures to reach dangerous levels at higher engine RPM. What’s going on? Metacritic. 1, Set the AC controls to MAX and RECIRCULATE 2. Answer A is wrong. 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. If the high and low gauges read 0, the system is empty. 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. We want nice stable conditions when testing. When needed, low blower speed can be used to force low side pressure down during testing and adjustment of compressor cut-out pressure. The area we would measure is in the evaporator box, and not accessible for this purpose. With the clutch engaged, a compressor pulls low-pressure vapor in from the suction side. The smaller scales near the middle of the gauge list the temperature relationship of different refrigerants. 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. See: http://www.aircondition.com/tech/questions/53/. The red, high side gauge is used to measure the high pressure side of the a/c system. If both gauges do not move, the compressor is not pumping. TVGuide.com . In most cases, their diagrams are right from the factory manuals. For this, you need a set of A/C service gauges. We could add or remove refrigerant and still nothing would happen. Tachometer Display Failure 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. Those that appear to be stuck closed may have inlet screens clogged with ground up desiccant particles. 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. Here I explain some simple troubleshooting techniques. With static pressure, you will only know if the system has some amount of liquid refrigerant present. 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. CBS News. Your static pressure should be no lower than 50 psi when leak testing. Author: Mike Thomas. A. This entry was posted in Auto Repair Tips, Automotive Tips, Tips on by ATC. Well, unfortunately, questions like that are almost impossible to answer without detailed information. If the high and low gauges read 0, the system is empty. That's where the manifold gauge set comes into play. We like to test with the system in MAX position on high blower with doors closed. However, in this post I’ll concentrate on understanding pressure readings to diagnose car AC issues. You won't get any cold air, but you should should start to see some compressor engagement. Any change of temperature brings with it a change of pressure. Bigger problem? There is a DIRECT relationship between ambient temperature at your location and the pressures you see on your gauges. When your car’s air conditioning stops working, it can be exceptionally frustrating. Suggestions. AC System Diagnosis. It can be used for recharging refrigerant, or to diagnose an a/c system based on pressure readings from your gauges. • You must use a pressure temperature chart or be using diagnostic gauges. Most low pressure switches require at leas 20-psi before they’ll engage the compressor clutch. At this point, he compressor will kick back on and the cycle will repeat itself. That allows the high and low pressures to equalize. A faulty automotive air conditioner can be one of the more difficult issues to diagnose and repair. Auto AC Troubleshooting Guide Some things you can check, even before bringing your car to us. 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. They include wiring diagrams and technical service bulletins. 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. My air conditioning was working last week, and then it quit working. This is called short cycling. Low blower speed will reduce heat load on the evaporator to the point where compressor cycling can occur. Typically, all systems today contain R-134A refrigerant. R134a low side pressure will be be slightly lower (27 PSI) at this temperature. many car stores rent these tools for customers for a fee. Comments are closed. Let's take the fixed orifice tube system for example. This can be purchased over the counter at most auto parts stores. On that same 80 degree day we would see between 176 and 200 PSI on the high side of an R134a system. What my bother is doing is watching until the temperature stops dropping or starts to rise and says stop. And it's easy to reach in and feel how cold the vent temps are getting. This is because electric condenser fans are fixed in speed, and will not compensate for high engine RPM. So, In most cases, you will need a static pressure of at least 45 psi before you begin to see the compressor operate. Technician B says if the needle moves more than .01 "hg after the evacuation process is complete, the system should be inspected for leaks. 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. It goes something like this. It's not producing suction, and it's not producing pressure. Car A C Pressure Chart. The same holds true on rear wheel drive cars with engine driven fans. The TXV is very efficient and is designed to tightly control liquid refrigerant from spilling out of the evaporator. 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? 4. MAX (recirculate) mode is preferred since we'll need to have the hood up while charging and testing. If engine speed needs to be substantially increased to bring pressures in range, that's a sign that the compressor is getting weak. A/C System Troubleshooting (Pg 1) HFC 134a A/C TROUBLE SHOOTING I (REFRIGERATION CIRCUIT ... For Insufficient Cooling . Close the doors. A clogged orifice tube will starve a compressor of oil. 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