A high low side reading (with usual high side reading) is often the result of a malfunction in the thermostat switch. 3) Partial blockage of the orifice tube/expansion valve and the evaporator. Overcharged System: The other reason you might be experiencing high pressure is even when the engine is off is that your whole air conditioning system has been overcharged. Pressure Range Low side: 0 to -29.99 psi High side: 71 to 85 psi Indications Low pressure side becomes a vacuum High pressure as listed above Frost or condensation on the front and rear pipe connections of the receiver dryer or expansion valve Causes AC system is blocked by contamination or ice And for a lot of drivers this is something they may let slide for a while since air conditioning is not required for the proper functioning of a vehicle. The system should be about 25 to 30 psi on the low side and 200 to 250 psi on the high side. One of the problems that can pop up with your air conditioning is when the pressure on the low side of the compressor is running high, while the pressure at the high side of the, Determining the pressure in your AC system is not entirely difficult to do. Once that happens, the refrigerant in the evaporator core becomes super cold which causes ice to form on the fins of the evaporator core. A bad check valve on an air conditioner, heat pump or similar HVACR equipment can show up as abnormally low or abnormally high suction line pressures, or as abnormally low or high superheat. Low head pressure may occur simulataneously with high pressure on the suction side of an air conditioner, heat pump or refrigeration system compressor system. However, if there’s a restriction on the high side of the system in the receiver/dryer, a crimped tube in the condenser or crud accumulation in the condenser or the expansion valve or orifice tube, there’s … (very common especially if you’ve tried to add refrigerant yourself). Therefore, you should get this part replaced or checked by an experienced mechanic. But if you see the AC low side high, high side low , such as the low side is 100 and the high side is 150, there might be problems with any of the inner components. The expansion valve controls the flow so that it stays at optimal levels and keeps the evaporator temperature where it needs to be. The pressure reading from the low side should be between 25 and 30 psi and the high side between 200 and 250 psi. If the expansion valve fails then the, What Happens When Your Heater Core Goes Out? This is the second part of a series on AC pressure gauge readings. Fix: Clean condenser fins and check for dented condenser tubes. Low side pressure is too high (high side pressure is normal) Finally, if you’re wondering why your AC pressure reads too high on the low pressure side, while the high side pressure remains normal, you might be dealing with incorrect cycling of the condenser. Fix: None needed. Replace expansion valve, flush and install in-line filter. The reason you have a high pressure side and a low pressure side at all is because the compressor increases the pressure and as it runs through your AC system to the condenser where it changes from a gas to a liquid and it will eventually lose pressure again as the cooling process takes place. The system is overcharged. He said he has not tried to put any refrigerant in it (I initially thought maybe it could be an overcharged system) The warm air eventually melts the ice inside the orifice tube or expansion valve and it begins working again. It's also possible that air has gotten into the coolant system and is raising the pressure as well. . 3) The heater core is leaking warm coolant into the heater box. And for a lot of drivers this is something they may let slide for a while since air conditioning is not required for the proper functioning of a vehicle. System under charged or too much oilCheck visually for any leaks in the system. For example, it is currently 81 degrees outside. The receiver / dryer is part of your air conditioning system that stores and dries the AC refrigerant. l. Defective winding Or 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? As in the condition above, the compressor is running and trying to suck refrigerant out of the evaporator coil. Let us go through the causes and solutions of these vital dilemmas here. That way you can at least tell for yourself that this is the main issue and not one of the other host of issues that could potentially cause problems with your car's air conditioner. Engine Problems Chevy Equinox: Will You Stand Excessive Oil Consumption and Complete Engine Failure? It's possible that you might have a problem with your pressure switch, your expansion valve, or the receiver / dryer also. The expansion valve failing is another thing that can cause the pressure on the low side to go too high and the high side to go too low. Compressor turns off then slowly goes back to about 30 psi. This could be the result of a problem with your thermostat switch or temperature gauge but you're going to need a mechanic to diagnose this one properly for you. 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