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AC Compressor Pressure Readings & their Meaning
I need some information on what the correct pressure is on the low pressure port for AC in these cars. I am basically trying to see if dealer was trying to scam me Dealer promptly tells wife that she cannot use AC or compressor will make car stall out. In short, I buy pressure gauge at Autozone to check pressure; low port was !!!!
I reduced range down to 45 and now compressor and system is working perfectly. So is 45 PSI max the range for low side? Is is possible the over pressure was done to ruin compressor intentionally or is it an actual compressor problem? What pressures did it show before they added more refrigerant? AC was working fine I am now fairly certain that the system was overcharged, so don't go to Medford Volvo in Dothan, Alabama. Just had to vent my frustration at a job poorly done by that dealer.
Yeah, got to learn to trust yourself, mechanics don't necessarily know your car as well as you do. Bookmarks Bookmarks Facebook Twitter Digg del. All times are GMT The time now is PM.
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Be sure to leave a comment or question on anything that may interest you. You can also send an email to our pro for direct assistance! Knowing what the pressures are in the air conditioning system in your car can tell you almost all you need to know about how your system is functioning.
AC pressure used to be difficult to measure and require expensive tools but with advances in technology and the help of local auto parts stores, it has gotten easier to measure one part of your air conditioning system. AC refill cans are readily available at your local auto parts stores and even at many larger stores.
These gauges are relatively accurate and an inexpensive way to measure the low side pressure in your system. Unfortunately, the low side pressure is just one piece of the puzzle.
Your air conditioning system is split in half when it comes to pressure. Your air conditioning system holds a very high pressure between your AC compressor and condenser up expansion valve, and a relatively low pressure after the expansion valve and evaporator and back to the inlet of the compressor. The can of refrigerant you purchased from the auto parts store is pressurized so it can push the new refrigerant into the system.
To make sure you get as much refrigerant out of the can and into your system, you connect it to the lower pressure side of the system so it is the low side pressure that you see measured on the gauge on your refill can.
To measure the pressure in the high-pressure side of your system, you need a little fancier piece of equipment. The best way to measure the high-pressure side of your system is to get the proper tools for a local auto parts store.
Pressures can vary from car to car based on the system and the pressure in your system will also vary with the ambient temperature. The warmer it is outside, the higher the pressure will be. For a general reference, you can check out this chart of Ra system pressures. A low pressure on the low side could also indicate a clog somewhere in your system.
Most problems with your air conditioning system will require a vacuum, repair, and refill of the system. I installed it, and I saw on internet I have to add oil in it before to fill it with refrigerant, but which oil I have to add, and how many???
My car is a chevrolet Camaro RS 3.Stephen Blog Leave a comment 6, Views. Your AC is not working properly. No matter what you do, your car still feels like an oven. If this is the case, then there might be an issue with the compressor, or the refrigerant may be leaking out. You just need to check the pressure readings. But, what if the readings say that the AC pressure is too high, especially the low side pressure? Well, the pressure readings of your AC system is what indicates whether the AC is functioning properly, or if there are underlying problems, such as leaking refrigerant, system damage, or worse, compressor failure, which can easily cost you a fortune in repairs.
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.
The correct pressure readings depend on what car you have, and you can find the correct numbers out from your car manual.
Low readings mean that there is almost no refrigerant, which may be caused by leakage, while high readings suggest that the system is overcharged. If either of these scenarios is the case, you need to either check for leaks and have any issues repaired before filling up the system with refrigerant to the correct specifications, or have a mechanic safely release pressure off of the AC system.
When the engine is on and the AC is on high, low pressure readings should be around 30 psi and the high pressure side should be about psi depending on your car.
The correct reading will display once the clutch engages and the gauge stops cycling. If there are readings on both the high and low sides but they are not the correct specified pressures, it means that certain parts of the AC system are not functioning properly, such as the expansion valve, compressor, and clutch. I have talked a bit on what the correct AC pressure readings should be, and what are the common issues that you might be encountering if the readings are wrong.
This high pressure is commonly caused by two problems:. First, there might be debris blocking the flow of air from the condenser fan motor, or the motor itself is damaged, leading to little to no airflow through the condenser.
This means that the condenser fan cannot efficiently and quickly cool the AC system. A highly pressurized condenser fan results in distortion of the aluminum in the compressor, as well as leakage from the evaporator coils.
When these things happen, repair costs can easily reach a thousand dollars. The other usual cause of high pressure readings is that the entire AC system may be overcharged, which happens either when there is too much refrigerant or too much oil. In this case, pressure must be released by a certified mechanic. You might get a false high reading if the engine is running or if air enters the system. Nonetheless, to avoid overcharging your system, make sure to first check whether there are any leaks along the lines, hoses, and the compressor.Our Address.
Kings Mills, OH Anyway, I hooked up my manifold gauges and the low side pressure maxed out the gauge! The high side pressure was roughly The car will not turn the AC compressor on, probably because these pressure are out of wack.
He said he has not tried to put any refrigerant in it I initially thought maybe it could be an overcharged system. The compressor was not running and the low side gauge is buried because it only goes to psi. You could have a lp switch issue. Thanks for the reply. Sorry for the delayed response. So my understanding is that the low pressure switch monitors the low side of the AC system and turns OFF the compressor when the pressure is too high.
I am getting no compressor clutch engagement at all. Am I wrong in this???? EDIT: Standing pressure actually makes me go back to the expansion valve being bad.
If it is open all the time, then the compressor is pressurizing the entire system, which would cause the low side to go high until the pressure switch kicks if off. It also fits with the earlier symptoms of the AC randomly not working before it went out completely. So do you have psi without operating the compressor? Is the clutch stuck, and turning the compressor even without the engagement solenoid being energised?
What do my car AC pressures mean?
Low side pressure should be 35 psi, high side around psi. Engine off, both sides will equalize to around 70 psi. And no the clutch is not stuck. I can turn the clutch with my hand independently of the pulley when running. Be careful posting such a statement on a public forum.So you will definitely need a set of pressure gauges to diagnose this symptom.
Refrigerant is a gas that changes states through pressure which is also how it changes temperature. Click on the image to get a detailed description of the gauges needed to check your system.
These pressures will vary depending on ambient temperature temperature of the outside atmospherebut ideally, you will want to see your low side pressure between psi and your high side pressure between psi.
If one or both are out of that spec, see the options below to start looking further into your problem. Check visually for any leaks in the system. If you are low on refrigerant, it leaked out somewhere. Look for oil residue around the hose ferrules, fitting connections at the compressor, condenser, and evaporator or expansion device. If no obvious leak is found, recover the refrigerant and replace the service ports or valves, evacuate and recharge the system, and add dye in case there is another leak.
Evacuation and recharge should be performed by a licensed professional with the proper machinery. Evacuation should be done with a proper vacuum pump that can bring the system down to at least Pulling the system down to a vacuum reduces the boiling point and any moisture in the system is then boiled and turned into a vapor to be removed.
This also ensures that all the air has been removed from the system. Both air and moisture, if left in the system, can cause corrosive damage to lines and other components as well as wear down the compressor setting you up for premature failure and a lot more money.
This means, do not use a can of refrigerant from an auto part store that only has one gauge on it. You need gauges, a vacuum pump, and a scale to do this correctly. If you do not have these things, take your car to a shop. Once the vacuum is complete, let it sit for about 5 minutes to see if you lose vacuum pressure.
This will indicate that you still have a leak somewhere. Your underhood sticker should inform you of how much refrigerant your system holds and what type of oil to use. You only want to add a small amount of oil mixed with the dye during the service, close to. When done, run the vehicle with the gauges still connected and record new pressures.
If it is blowing cold now… go enjoy the cool air! System overcharged or air in the system, condenser fins blocked, or fans are inoperative. Check and make sure the condenser fan is turning on.Static pressure is the pressure with the system at rest compressor off for at least mins.
Attach to the hoses and gauge set to the high and low side ports of your AC system. These are the readings you should see based on ambient temperatures with a system filled with Ra refrigerant.
If the static pressures are close to the numbers shown on the chart, it only tells you two things:. If the static pressure is lower than the threshold for the low-pressure limit switch on your particular vehicle, the AC system will not engage the compressor and you will not get any cooling. If the static pressure is higher than the threshold for the high-pressure limit switch on your particular vehicle, the AC system will not engage the compressor and you will not get any cooling. Plus, venting refrigerant can cause frostbite.
This means the low-pressure switch will be operational and when you turn on the AC, you should see the compressor clutch engage. In other words, you can start the engine and turn on the AC. Once you start the engine and turn on the AC, the compressor should run. If the system is low on refrigerant charge, the clutch will quickly disengage. Since the refrigerant charge is too low, not enough new refrigerant is replacing the suctioned refrigerant and that causes the pressure to fall below the low-pressure switch threshold.
So it turns off the compressor. Generally speaking, you want around psi on the low side and on the high side. Why psi? Because, on an Ra AC system, psi. On the high side, Ra pressures usually run 2. At psi. NOTE: High humidity and airflow velocity effect evaporator and condenser pressure readings. Blower set to HIGH speed 3.
Close the doors. Windows can be open. Is it a cycling clutch orifice tube system or an expansion valves system? See this post to learn what type of AC system is in your vehicle. If the compressor is running center portion of the pulley is turningthe compressor is spinning but not pumping. Check to make sure the radiator fans are working at the proper speeds.
Evacuate the system and recharge with the correct refrigerant charge and test again. Symptom: Low cooling Pressure readings: Low side is low.
High side normal to slightly low Causes: Low on refrigerant charge. In this case, the evaporator is starved for refrigerant. In a fixed orifice tube system, you want the evaporator almost completely full of refrigerant.
When properly charged, a full evaporator will spill some boiling refrigerant into the accumulator where it will continue to vaporize before entering the compressor. However, if the system is low on charge, the evaporator is only partially filled with refrigerant, so half of it will be cold and the other half hot. This often causes evaporator icing, where ice builds up on the evaporator.
The ice blocks airflow and the low pressure triggers the low-pressure switch. Keep in mind that AC works when the refrigerant removes just enough heat from the air to cause the refrigerant to change from a liquid to a vapor.
However, in a partially filled evaporator, the vapor then absorbs heat. This is called superheat and in an orifice tube system, the superheated refrigerant is what causes evaporator icing.For more information about conducting tests using temperature probes, see this post. Many sources tell you to start your charge diagnosis by checking static pressure. Measure static pressure with the engine off and AC not run for at least one hour.
That allows the high and low pressures to equalize. But static pressure readings can only tell whether the system is completely empty or has some refrigerant in it. It can never tell you whether the charge is correct! Well, Ra boils at 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.
If your static pressure shows more than that, the compressor clutch should engage. If the high and low gauges read 0, the system is empty. The ONLY way to know if your system is properly charged is to evacuate it and add new refrigerant with a scale.
What Should my AC Pressure Be?
The same applies if your system is overcharged. Measure temperature about 1-ft in front of the grille. This is really important.Online HVAC Training
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. 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.
Click on the image above and find the type of refrigerant metering device your vehicle uses. What is this so important? Because expansion valve systems usually show show a lower suction side pressure than an orifice tube system. See the pressure chart below to see what I mean. Unscrew the protective port caps and store in a safe place. Connect the quick release connectors to the service ports on the high and low side refrigerant hoses. Some low pressure ports are located on the accumulator, while others are located on the metal portion of the lines.
AC manifold gauges show system is low on charge. Here the gauges show lower than normal pressures on both the high and low sides. This is an indication of a low charge. Unlike the cheaper Haynes and Chilton manuals that cover multiple year models, leaving the exact information you need to fix your car, these professional manuals cover your exact year, make, model.
Plus, they contain full trouble code descriptions and troubleshooting instructions. Pricing: Eautorepair. 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. However, Alldatadiy. If you need to dig into your doors, dash or console, Alldatadiy.
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