ac pressure troubleshooting chart

2021/05/21

Yeah, its just like a furnace filter. Check the defrost controls for proper operation and add more defrost First, it picks up enough heat to cause the refrigerant to change state from liquid to gas.

You need to verify what is wrong before replacing any parts. the compressor for the maximum suction pressure. For more information on normal AC pressures, see the charts below. conditions. No bleed resistor on the start capacitor. Is it a cycling clutch orifice tube system or an expansion valves system? Does the start capacitor If the suction line is cold with the system operating, there is usually enough refrigerant in the system to perform the leak test. Copyright 2022 Buy Auto Parts. Since the temperature is near the freezing point of water right at the orifice tube, the moisture freezes, cutting off the flow of refrigerant into the evaporator. The expansion valve, solenoid valve or the compressor The recovery unit will continue to operate, drawing in air from the leak source and adding it to the storage tank. However, Alldatadiy.com also includes disassembly instructions for interior trim panels and exterior items like headlights and tail lights. on an R-134a system. However, recycling equipment with a manually operated purge can allow high levels of air into the system usually due to technician error. This often causes evaporator icing, where ice builds up on the evaporator. So, if you really want to diagnose and fix your AC system yourself. Rerun the load Incorrect capacitor, capacitor voltage rating too Compressor malfunctioning, possibly leaking valve. Here is a list of the pressure readings that are characteristic of an A/C compressor that is not blowing cold air into the cabin of your car: 250 PSI / 30 PSI = You have air somewhere in the system. Turn on the leak detector. Expansion valve or metering device too large. conditions. a condenser. External equalizer lines tapped at a common point Get the BEST auto repair information Alldatadiy.com and Eautorepair.net are professional-grade shop manualsperiod. Low suction pressure due to a liquid line restriction. The compressor will shut off once the low pressure triggers the low-pressure switch. For more troubleshooting tips using gauges, see this post. Too much oil will reduce the cooling capacity of the system. In fact, adding too much may cause the A/C system lubricant additives and viscosity to break down. Flooded head pressure control: Hot gas bypass line Defective oil pump or the oil pump inlet screen They should be the same because the high and low side pressure equalize once the compressor shuts off. That saves a lot of time because you dont have to refer back to the component locator or circuit locations. However, adding more than specified to the A/C system will not make the leaks more obvious. As stated earlier, most refrigerant leaks will be found at fittings and connections. The moisture travels with the refrigerant.

Place a temperature gauge in one of the air outlets in the passenger compartment. Without refrigerant identification equipment, the refrigerant containing only air would not be saved because the actual problem could not be identified with Go/No-Go equipment. Suction pressure high - High Restriction in the low side of the system. This is common on walk in coolers and freezers when So, if the ambient temperature is 80F, youll see high side pressures running between 176-psi and 200-psi. An operational test will help you verify that all HVAC system controls and modes are operating correctly. Evacuate the system and recharge with the correct refrigerant charge and test again. If R-134a has not been identified as 98 percent pure, the vehicles A/C system should not be serviced with dedicated equipment. wax. Be careful; high-pressure refrigerant lines may become very hot! For example, a restricted orifice tube will cause the compressor to suck, but the restriction/clog in the orifice tube prevents the full flow of refrigerant, causing evaporator starvation. Shine an ultraviolet lamp on the A/C system and look for traces of dye, indicating leaks. Check the bottom of the evaporator housing for oil, because oil often accumulates there when the evaporator fails. 5. Normal compressor cycling on a rack system. the orifice tube is too large the orifice tube has been replaced and the O-ring isnt seated properly. If you need to dig into your doors, dash or console, Alldatadiy.com is the better choice because Eautorepair.net doesnt any interior or exterior trim or body part removal.

A possibility exists that a small leak may occur without any signs of trace dye. See this post to learn what type of AC system is in your vehicle. This will eliminate confusion regarding any leaks in the future. 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? Why 27-psi? If the refrigerant in a system contains excess air but has no other problem, removing the air will resolve a high pressure or loss of performance problem. youll need an AC manifold gauge set and hoses. There should be no more than 5 degrees However, knowing what the gauges say can be troublesome for some technicians. occurrence when an oversized outdoor weather hood has been installed. (function() { If the container pressure is not checked, air will transfer into the system. Maintenance Advantage program. material causing liquid flood back. Has someone Both temperatures are usually needed to analyze system performance. variable speed motor or a flooded head pressure control system. Internally equalized expansion valve used on a Flooded head pressure control: Field adjustable If the actuator moves but the air door doesnt try moving the door by hand. Therefore, you must allow enough time for dye to circulate. Excessive pressure drop in the liquid line due Many leaks are the result of normal engine vibration, which loosen fittings and may lead to metal fatigue and cracks on metal lines over a period of time. of control is based on pressure. If the coolant level is low, this may indicate that air is trapped in the heater core. The engine temperature gauge is normal, but I have no heat!. open. or defective. They are just a guide to aid you in your diagnosis. freeze up when this occurs. 3. Expansion valve power element has failed or lost If the compressor is running (center portion of the pulley is turning), the compressor is spinning but not pumping. Any time more than 0.5 lb. break down of the insulation between the terminals and the compressor of the evaporator will freeze up when this occurs. Un-insulated receiver exposed to low ambient. Once the evaporator ices over, you should notice a dramatic reduction in airflow from the vents. 200 PSI / 70 PSI = There is a blockage somewhere in your system either before or at the expansion device. 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. During the visual inspection, be sure to check the service fittings after removing the gauges. System contamination, probably moisture or rarely, Check the specifications chart air cfm pressure ac airflow blower flow residential ton evaporator coil tool performing setup figure system through Caution must be taken when flammable refrigerants have been detected, including the use of special air-powered recovery equipment. If the flash gas is not acceptable, Now that you are familiar with some diagnostic testing methods, it is time to evaluate some of the more common diagnostic scenarios you may encounter. Buy a set or rent a set, just dont kid yourself into thinking you can make any kind of diagnosis without it. In this manner, refrigerants change states as required by the system. There are also a few techniques that will help confirm your suspicions regarding those pressure gauge readings. Incorrect expansion valve power head charge. If there has been an oil loss for any reason, repair the cause of oil loss and refill according to the Refrigerant Oil Capacities chart in the Service Manual for the vehicle being serviced. Re-circulating of condenser air. although there is more than one expansion valve on the same system. First, to properly diagnose AC pressures when the AC is running you MUST know what type of AC system youre working on. Flood back due to poor distribution of refrigerant Too little oil will damage the compressor. Using a Go/No-Go refrigerant detector for both service situations can only identify system contamination. with corresponding fluctuating in the suction pressure. the condensing unit is mounted on the box and closed off by a drop Check the evaporator, piping, and expansion valve to locate the source of the issue. In any case, these components must be repaired or replaced to prevent additional refrigerant loss. Electronic leak detectors must meet or exceed SAE J1627 to operate properly on R-134a. Ruptured suction line to the liquid line heat exchanger. Improper mounting of the relay. Check to make sure the radiator fans are working at the proper speeds. You cant accurately diagnose your cars AC by using just the low-pressure gauge on a recharge kit because youre only seeing pressure on the suction or low side of the entire system. 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. the header. Pressure Regulator (CPR) or pressure limited TXV (MOP) may be required. 1, Set the AC controls to MAX and RECIRCULATE 2. NOTE: Too much dye can affect the viscosity of the refrigerant oil. Uninsulated receiver in a cold ambient acting as If both pressures are equal, the refrigerant is considered acceptable. Air flow is restricted thru the condenser. Ask questions about past changes. 225 PSI / 80 PSI = It is likely that the expansion valve is opened too wide (not the case if your A/C system has an orifice tube) Also, you could have too much refrigerant in the system. Read the pressure gauges and compare them to factory specifications. NOTE: All Nissan vehicles are originally built with refrigerant trace dye (usually a pellet placed in the Rec. Defective temperature or pressure control. In a fixed orifice tube system, you want the evaporator almost completely full of refrigerant. ceiling. If not, refrigerant pressure can be supplied from a charging station although it is not necessary to completely charge a system for leak testing. Synthetic-based PAG oils are used with R-134a systems. If your readings are outside the typical pressure/temperature range, see below. Obviously the main issue that people deal with when they have a broken A/C system is that the air coming out the vents is not cold enough. NOTE: Trace dye is mixed with the PAG lubrication oil. valve. If your pressure gauge readings are not within factory specifications, there is a problem in the system. above the design conditions. is too warm. a refrigerant distributor. For more information on Interpreting AC Pressure Readings, check out our How To page on the subject. damage or an internal restriction. Alldatadiy.com, on the other hand, uses the factory diagrams.

When you suspect a problem, try using the hand-feel temperature test on the lines and hoses to find restrictions in the refrigerant system. As you go over the system, using the black light to check for indications of trace dye, do not forget to check the evaporator condensate drain.

Search for leaks by slowly moving the sensor tip over all system components, including controls, seals and fittings. No traps or insufficient traps in the suction riser. not acceptable, change to a control based on ambient air temperature, 3. The overfeeding of expansion valve on a multi evaporator Damaged valves or rods in the compressor. Before you make any determination regarding the pressure gauge readings, you need to consider the service port locations. change to a control based on ambient air temperature, variable speed

The pattern will repeat over and over. Air Conditioning (A/C) pressure diagnosis can also help pinpoint the concern with a malfunctioning system. power element charge. While small leaks of a few ounces of refrigerant per year are difficult to detect, larger leaks of about a pound per year can easily be isolated. Usually the bottom rows of the evaporator will Incorrect starting relay. Let the system operate for 5 minutes.

up. Turn off the A/C system and the vehicle. Flooded head pressure control: Bypass port wedged flow. Liquid migration on the off cycle. The tester will emit a sound when the sensing tip detects refrigerant gases. Moisture in the system reacts with the refrigerant and oil to form acids and sludge that clog orifice tube screen Moisture in the system that freezes at the orifice tube and restricts refrigerant flow through the orifice. If the cabin air temp is controlled by an air temp/blend door, check actuator operation to see if it moves as you change the temperature setting. 1. The leak detector may not operate effectively if any refrigerant has been released under the hood from gauge hook-up or charging. This also applies to trace dye; therefore, only use trace dye that meets or exceeds Nissan or Infiniti approval. Product, people, heat producing equipment in Excessive load on the evaporator above the design Go to www.NNAnet.com and click on the Maintenance Advantage link. A tool that can identify the contents of an A/C system is essential in some diagnostic situations. High side normal to slightly low Causes: Low on refrigerant charge. Crankcase heater not installed or defective (migration). An A/C System that is working properly should have 150 PSI on the high side and 30 PSI on the low side. Gauge readings may not always indicate the same pressure throughout the entire high side or low side of the system. Start the engine and turn on the A/C system. In some cases, the fix can be as simple as replacing an actuator. in the compressor. Even with the fan turned up high, it does not seem to ever blow cool air!. Fans and blowers move fresh or recirculated air across the evaporator fins and heater core to provide heated air for the climate control system. Excessive refrigerant on non receiver system. down controls and a crankcase heater. Many DIYers replace AC parts only to discover a clogged cabin air filter after spending hundreds on parts. We ship from multiple warehouses across the country, so you get your part as soon as possible. NOTE: Refer to the HA section in the ESM for the applicable vehicle for pressure readings at various ambient temperatures and the setting the AC should be on when diagnosing with pressure gauge readings. Diagnosis and Repair of Under Hood Components. have a bleed resistor? The electronic leak detector is a portable, electronic gas detector. discharge valve leaks. system with too much pressure drop thru the evaporator or used with horsepower and blade size, compared to the specifications of the

More importantly, the eyeglasses protect your eyes from damaging ultraviolet light. In other words, the low refrigerant charge causes the refrigerant is in the system to sit too long in the evaporator. poor air distribution. Leaking hot gas defrost solenoid or hot gas bypass its charge. If so, then check the low side Look, I know you want to figure out your AC problem yourself without buying any tools, but you can really screw up your cars AC if you overcharge or undercharge the system. Leakage can usually be traced to loose fittings, deteriorated hoses or seals, or damaged metal lines. A large puddle is an indication of evaporator ice that has melted and drained onto the ground. This may be a situation where the AC is working fine but the heat is on, diminishing the effects of the AC. of a Crankcase Pressure Regulator (CPR) or pressure limited TXV If the recovery unit has a properly operating automatic purge, usually it will vent the excess air. Defective compressor overload which will cause var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); Flooded head pressure control: Bypass condenser Check the arrow Insufficient refrigerant charge, usually accompanied Water cooled: Defective water regulating valve. on the side of the relay, it should be pointing up. Some units also indicate air concentration in addition to purity levels. Trace dye comes in different forms for a variety of fluids including: engine oil, transmission oil and engine coolant. Low and high side pressures are about the same (like 80-psi low side and 80-psi high side) AND you have to increase RPM quite a bit to get pressures into the normal range AND you notice the air only gets cold when youre driving AND youve ruled out a low refrigerant charge or bad orifice tube/expansion valve. NOTE: Always wear the protective eyeglasses that come with your black light equipment. To clean the evaporator coil, use a foaming chemical cleaner.

F difference in the superheat between any two circuits as they enter Because, on an R-134a AC system, 27-psi. If youre tracking down a wiring issue, Eautorepair.net is the better choice. 2. This will enhance the luminescence of the dye, which will make the smaller leaks more apparent. Place a second temperature gauge at the condenser to measure ambient (outside) air temperature. We have reviewed over 1,000,000 fitments to guarantee an exact fit for your vehicle.

Close the doors. control. They include wiring diagrams and technical service bulletins. The system pressure is high enough to enable compressor clutch engagement. Any trace dye coming out of this location is a sure sign of an evaporator leak. Remember, these are the locations on the system where your gauges actually monitor the pressure. Start winding staying in the circuit too long. Experts in auto parts since 1989-We are rated 4.9/5 by over 400,000 of our customers. If the detected gas contains a hydrocarbon (flammable material), the unit sounds an alarm and displays HC. Remember that the lubricant transports trace dye, and if the lubricant never reaches a leak source, no visual indications will be present.

Water cooled: The cooling tower is cycling due var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; The load is too high. This is a common Electronic leak detectors are an accurate way of locating even the most elusive refrigerant leaks. (0.23 kg) of refrigerant is required to charge the system over a period of a year, a leak is present. Low side pressure drops below low-pressure switch threshold, which shuts off the compressor. (MOP) may be required. on your gauge means the refrigerant will produce about 32F at the evaporator (as long as the orifice tube/expansion valve is operating properly and theres no air in the system thats artificially inflating the pressure to 27-psi). Poor distribution of refrigerant thru the evaporator Oil pressure control defective or improperly wired. Rubber hoses deteriorate over time and rubber particles clog the orifice tube screen. Trace dye is mixed with a small amount of refrigerant lubricant. If the terminal has threaded studs and nuts, a

Equipment with an automatic air purge usually keeps the air contamination level at less than 2 percent by weight, which is considered acceptable. warm, condenser tubes restricted or defective water regulating valve. Incorrect air flow thru the condenser. THEN, the gas absorbs even more heat from the evaporator airflow, causing evaporator temperature to fall below the freezing point of water. If its clogged, it can restrict airflow. calculations. Liquid refrigerant backed up in the receiver. Recovery/recycling equipment that has a manual air purge should be checked every day before the recycled refrigerant is used. The unit displays FAIL if R-134a gas has not been identified or if it is not at least 98 percent pure. Liquid line solenoid valve leaking during the off for summer application. thru the evaporator nozzle and circuits. NOTE: High humidity and airflow velocity across the evaporator and condenser have a direct effect on pressure readings. Expansion valve bulb and / or equalizer tube located troubleshooting ac guide reading ask questions trutechtools lonely downloadable resources Check the performance charts of _gaq.push(['_setAccount', 'UA-4776845-1']); Expansion valve defective or has the incorrect To access the evaporator coil, remove the blower motor resistor, and take a peek inside. Regardless of which type you have, all of them require some type of periodic maintenance to perform accurately. This creates the possibility of flooding on start Control voltage too high, causing premature trip Look for heater hoses and either a cable or vacuum hoses running to a valve. Refrigerants are the vital working fluids in refrigeration systems. However, if the system contains air and/or other refrigerants (for example, blended refrigerants), then the contaminated refrigerant must be removed with special recovery equipment and sent off-site for processing or destruction. Find the leak and fix before refilling. You need to use these readings, other symptoms, the Service Manual and your knowledge of system operation to find the trouble with the system. If this is a problem, use low-pressure compressed air or a fan to blow any released refrigerant from the engine compartment before leak testing. However, ambient humidity also affects how your cars AC works because high humidity changes how the heat transfers. Tight bearings or mechanical damage in the compressor.

If the air is not removed from the system, the system will have performance problems. High supply voltage, light compressor load. If the low and high side gauges read the same pressures and the readings correlate to the pressures/temperatures shown on the chart above, they only tell you two things: If the static pressure is lower than 27-psi.

Condenser may be blocked. The J-43926 Air Conditioning Dye Kit provides you with a method for adding trace dye to the A/C system. 250 PSI / 50 PSI = The system is overcharged and the condenser is not cooling. chart pressure temperature superheat subcooling waterproof refrigerants Check amp draw verses suction pressure verses condensing temperature Lack of an oil separator on freezer systems. hot gas bypass valve or capacity control valve. var _gaq = _gaq || []; If the gauge reading goes back to a very low suction-side reading, the orifice tube or expansion valve screen is likely frozen. Superheat setting on expansion valve too high. Then youll get cold air againuntil the evaporator ices up again. 100 PSI /100 PSI = The compressor is not engaging because there is no power coming to it or you have a burnt coil. For More Free Troubleshooting Information Please Visit Our Home Page. NOTE: For more information regarding refrigerant contamination or disposal locations, contact the Environmental Protection Agency (EPA) hotline at 800-296-1996 or over the Internet at www.EPA.GOV/ozone. NOTE: Low airflow across the evaporator, caused by a plugged cabin air filter, can mimic the symptoms of a low refrigerant charge. document.getElementById( "ak_js" ).setAttribute( "value", ( new Date() ).getTime() ); Enter your email to receive an instant discount. })(); Oil trapping in the system. Water cooled: Restricted water flow, water too The equipment must be dedicated for the recovery of contaminated refrigerant only! The static pressure correlates to the temperature of the AC components under the hood, not outside in front of the vehicle. Overcharging actually REDUCES cooling and undercharging can damage the compressor (refrigerant carries the lubricating oil so low refrigerant = oil starvation for the compressor). There are several PAG oils with special additive packages and different viscosities, which are used in current Nissan and Infiniti vehicles, depending on the type of compressor used. Then checking cooling. If the gauges dont read the same during a static pressure test, it means: 1) You havent waited long enough for the pressures to equalize, or. The blower will melt the ice. You should also be aware that there are different types of electronic leak detectors. Leaves and dust can clog the fins of an evaporator coil, reducing its ability to remove heat from your car. A compressor overheating will break down the wiring connections. Generally speaking, you want around 27-psi on the low side and 200 on the high side. Metallic wear particles from the compressor clog the orifice tube screen. Partial load, low humidity, etc, without capacity Existing low ambient controls out of adjustment

If the A/C system is not cooling the vehicle to factory specifications: check to see if the A/C compressor clutch is engaged and the A/C system is fully charged. To perform top-quality A/C work, you will need to know if a container of recycled refrigerant is tainted with air. Keep in mind that you could have 100 percent pure refrigerant that could still be considered unacceptable due to high levels of non-condensable gas.

System undersized. Check operation of the low You may be required to add up to a pound of refrigerant in order to locate the leak. NOTE: You may have to increase the detection sensitivity of the sensing tip itself. body generally are the result of over tightening the nuts. Thats just around the freezing point of water. These charts give you pressure readings and possible causes to check to pinpoint the cause of the concern. Water cooled: Water is inadequate and the temperature The use of a Crankcase Liquid refrigerant feeding through the oil separator.

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