This is another reason why you still should use an electronic leak detector. Compressor - Loss of oil, Loss of oil pressure, or Cuts off on oil pressure control. The blower will melt the ice. Place a second temperature gauge at the condenser to measure ambient (outside) air temperature. The J-43926 Air Conditioning Dye Kit provides you with a method for adding trace dye to the A/C system. poor air distribution. down controls and a crankcase heater. If the recovery unit has a properly operating automatic purge, usually it will vent the excess air. Rubber hoses deteriorate over time and rubber particles clog the orifice tube screen. The tool may also be required for A/C service centers according to regulations in your area. 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. to freeze in the open position. Finally, always attach the trace dye identification sticker in the engine compartment close to the A/C decal. Place a temperature gauge in one of the air outlets in the passenger compartment. Electronic leak detectors are an accurate way of locating even the most elusive refrigerant leaks. Search for leaks by slowly moving the sensor tip over all system components, including controls, seals and fittings. variable speed motor or a flooded head pressure control system. Then youll get cold air againuntil the evaporator ices up again. An operational test will help you verify that all HVAC system controls and modes are operating correctly. Fans and blowers move fresh or recirculated air across the evaporator fins and heater core to provide heated air for the climate control system. Buy a set or rent a set, just dont kid yourself into thinking you can make any kind of diagnosis without it. 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. When properly charged, a full evaporator will spill some boiling refrigerant into the accumulator where it will continue to vaporize before entering the compressor. Symptom: Low cooling Pressure readings: Low side is low. For more troubleshooting tips using gauges, see this post. Crankcase heater not installed or defective (migration). In most cases, their diagrams are right from the factory manuals. Therefore, you must allow enough time for dye to circulate. Turn on the leak detector. 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. Smooth coolant flow through the heater core is critical for heat output. If the flash gas is not acceptable, Regardless of which type you have, all of them require some type of periodic maintenance to perform accurately. horsepower and blade size, compared to the specifications of the If your pressure gauge readings are not within factory specifications, there is a problem in the system. 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. The tester will emit a sound when the sensing tip detects refrigerant gases. The ice blocks airflow and the low pressure triggers the low-pressure switch. Restriction in the low side of the system. superheat at evaporator outlet. In fact, adding too much may cause the A/C system lubricant additives and viscosity to break down. wax. Water cooled: The cooling tower is cycling due for a leak. Restriction in the discharge line due to physical This reduces both refrigerant loss and time involved as in the case of trace dye. on the side of the relay, it should be pointing up. Its like trying to diagnose your overall health with only half of your blood pressure reading. Has there been a recent addition All rights reserved. You could have a low-pressure reading on the high-side gauge and still have a restriction on the high-pressure side of the system. Must choose Next Day Shipping at Checkout after entering code. Start the engine and turn on the A/C system. in the low side. 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. Oil pressure control defective or improperly wired. When it comes to refrigerant system problems, you will need to be able to make a diagnosis based on pressure gauge readings. High side normal to slightly low Causes: Low on refrigerant charge. High / low voltage, high amperage on 3 phase supply, Air in the system. Excessive liquid refrigerant returning to the compressor Windows can be open. NOTE: Trace dye is mixed with the PAG lubrication oil. Check the evaporator, piping, and expansion valve to locate the source of the issue. Get the BEST auto repair information Alldatadiy.com and Eautorepair.net are professional-grade shop manualsperiod. Interrupted pump down which will leave refrigerant Find the leak and fix before refilling. thru the evaporator nozzle and circuits. any two circuits as they enter the header. The overfeeding of expansion valve on a multi evaporator 2) The orifice tube, expansion valve, compressor reed valves or stuck or theres a severe restriction somewhere in the system thats preventing the pressure from equalizing. warm, condenser tubes restricted or defective water regulating valve. Experts in auto parts since 1989-We are rated 4.9/5 by over 400,000 of our customers. NOTE: You may have to increase the detection sensitivity of the sensing tip itself. Let the system operate for 5 minutes. This not only enables the system to operate efficiently but also ensures proper lubrication of the compressor. Suction pressure high - High its charge. An A/C System that is working properly should have 150 PSI on the high side and 30 PSI on the low side. or defective. This will eliminate confusion regarding any leaks in the future. Check the rotation, Low outside air temperature on an air cooled system. NOTE: High humidity and airflow velocity across the evaporator and condenser have a direct effect on pressure readings. nozzle and circuits. This is because these large leaks may sometimes leave the system completely empty. Improper mounting of the relay. system with too much pressure drop thru the evaporator or used with In other words, the low refrigerant charge causes the refrigerant is in the system to sit too long in the evaporator. An AC system leak allows moisture into the system. During the visual inspection, be sure to check the service fittings after removing the gauges. Diagnosis and Repair of Under Hood Components. previously installed a new fan motor or blade? The equipment must be dedicated for the recovery of contaminated refrigerant only! 150 PSI / >10 PSI = Your expansion valve might be stuck open, or there could be a leak somewhere you in your system. If youre tracking down a wiring issue, Eautorepair.net is the better choice. Check for hose leaks and porous or worn tubing. 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. However, Alldatadiy.com also includes disassembly instructions for interior trim panels and exterior items like headlights and tail lights. In this manner, refrigerants change states as required by the system. If both pressures are equal, the refrigerant is considered acceptable. In this case, the evaporator is starved for refrigerant. 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. body generally are the result of over tightening the nuts. Air Conditioning (A/C) pressure diagnosis can also help pinpoint the concern with a malfunctioning system. Also, a faulty evaporator temp sensor can prevent the system from shutting down once the evaporator has iced over. Tight bearings or mechanical damage in the compressor. Operate the A/C system for 5-10 minutes to circulate the dye throughout the system. change to a control based on ambient air temperature, variable speed Check amp draw verses suction pressure verses condensing temperature port wedged open due to a foreign material lodged in it. So we will take a look at pressure diagnosis, but we need to start by reviewing refrigerant and how to determine if it may be the cause of the concern. External equalizer lines tapped at a common point Using a Go/No-Go refrigerant detector for both service situations can only identify system contamination. If your readings are outside the typical pressure/temperature range, see below. running continuously. What are my A/C pressure readings telling me about my A/C system. Install pump 4. There should be no more than 5 degrees 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. The recovery unit will continue to operate, drawing in air from the leak source and adding it to the storage tank. break down of the insulation between the terminals and the compressor The use of a Crankcase Compare the pressure readings to the pressure-temperature chart below. Excessive suction pressure beyond the limits of Heat is absorbed into the refrigerant by evaporation and released through condensation. Check the performance charts of However, knowing what the gauges say can be troublesome for some technicians. If the gauge reading is normal when first turned on and stays normal for a few minutes, you get cold air and THEN low side goes low, thats a sign of moisture in the system. To find a leak with an electronic leak detector: 1. This may be a situation where the AC is working fine but the heat is on, diminishing the effects of the AC. a hot area, an attic or drop ceiling for example. External equalizer on the expansion valve plugged Oil, stains or dirt are good indications of a leak. 200 PSI / 70 PSI = There is a blockage somewhere in your system either before or at the expansion device. Relay contacts sticking. On some vehicles, you may be able to view the evaporator surface with the black light by removing the fin probe assembly. voltage out of balance. 2. Has someone Air flow is restricted thru the condenser. Incorrect air flow thru the condenser. cycles. Excessive suction pressure beyond the limits of 250 PSI / 50 PSI = The system is overcharged and the condenser is not cooling. Poor distribution of refrigerant thru the evaporator If the container pressure is not checked, air will transfer into the system. 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. 3. They are just a guide to aid you in your diagnosis. F difference in the superheat between any two circuits as they enter Electronic leak detectors must meet or exceed SAE J1627 to operate properly on R-134a. Thats just around the freezing point of water. In any case, these components must be repaired or replaced to prevent additional refrigerant loss. Water cooled: Water too cold or defective water Water cooled: Water is inadequate and the temperature Has the refrigerated space been increased in size? check the pressure dome settings. Fan cycle control: This is normal if this type 125 PSI / 30 PSI = The system is either not charged enough or you have too much oil in the compressor. line without a liquid injection valve. 1. Many refrigerant leaks can be found through a simple visual inspection. The pattern will repeat over and over. a refrigerant distributor. to defective or dirty components. 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. Uneven or inadequate evaporator loading due to Voltage out of balance on 3 phase systems. System undersized. If so, then check the low side freeze up when this occurs. Alldatadiy.com, on the other hand, uses the factory diagrams. Trace dye comes in different forms for a variety of fluids including: engine oil, transmission oil and engine coolant. The engine temperature gauge is normal, but I have no heat!. although there is more than one expansion valve on the same 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. Excessive accumulation of oil in the evaporator. We have reviewed over 1,000,000 fitments to guarantee an exact fit for your vehicle. 160 PSI / 10 PSI = It is possible that the evaporator is frosted, the low pressure piping is faulty, or the expansion valve might be clogged. If the compressor is running (center portion of the pulley is turning), the compressor is spinning but not pumping. is inconsistent. Flooded head pressure control: Pressure drop thru Chiller systems; frozen or slushed or low water Add minimal amounts of trace dye to the A/C system according to the dye manufacturers directions. Maintenance Advantage program. youll need an AC manifold gauge set and hoses. (MOP) may be required. Compressor malfunctioning, possibly leaking valve. Ruptured suction line to the liquid line heat exchanger. Superheat setting on expansion valve too high. More importantly, the eyeglasses protect your eyes from damaging ultraviolet light. The load is too high. Liquid migration on the off cycle. Usually the bottom rows of the evaporator will First, to properly diagnose AC pressures when the AC is running you MUST know what type of AC system youre working on. One of the benefits of using electronic leak detection is being able to detect leaks at the time of A/C service. Some units also indicate air concentration in addition to purity levels. in the compressor. Unbalanced system, load in excess of the design Check the front of the AC condenser (its in front of the radiator) to make sure the fins arent clogged. The ambient temperature surrounding the condenser Before you make any determination regarding the pressure gauge readings, you need to consider the service port locations. Look for heater hoses and either a cable or vacuum hoses running to a valve. Excessive refrigerant on non receiver system. If the fluctuating pressure is system where all the EPR valves are wide open. of control is based on pressure. 3. open. cycle. The expansion valve, solenoid valve or the compressor To locate the source of a large leak, listen for a hissing sound or spray some soapy water on components and look for bubbles. 4. They include wiring diagrams and technical service bulletins. OR, continue driving the vehicle with the blower on HIGH while monitoring airflow from the vents. Expansion valve bulb and / or equalizer tube located Determine if the vehicle has a heater control valve. controls are set incorrectly. THEN, the gas absorbs even more heat from the evaporator airflow, causing evaporator temperature to fall below the freezing point of water. Flooded head pressure control: Field adjustable If not, refrigerant pressure can be supplied from a charging station although it is not necessary to completely charge a system for leak testing. Control voltage too high, causing premature trip A higher percentage mixture (more than 50 percent) will decrease heater performance. Attach to the hoses and gauge set to the high and low side ports of your AC system. Liquid line solenoid valve leaking during the off It takes a while to equalize, thats why you must wait 30-mins to check static pressure. 2. above the design conditions. Or, if you can access the orifice tube, apply heat to the orifice tube as you watch system pressures. a condenser. the refrigerant entering the condenser will be around 130F. Depending on the symptoms, there are various reasons your customers heater might not be working. 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). Water cooled: Defective water regulating valve. or capped. 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. Internally equalized expansion valve used on a Low side pressure will increase to the point where the low-pressure switch activates the compressor. If the detected gas contains a hydrocarbon (flammable material), the unit sounds an alarm and displays HC. Generally speaking, you want around 27-psi on the low side and 200 on the high side. Incorrect starting relay. Refrigerant analyzers are available that meet or exceed SAE J2912 and can identify gas samples taken directly from the refrigerant system or storage containers. Low and High AC pressures are lower than recommended in an expansion valve system where the valve is located on the evaporator outlet.
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