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Car Forum / Ford / Ford Explorer / August 2007Air Conditioner pressure settings
Hi folk, My 1998 5.0 V-8 AWD is in need of more freon. Could someone please tell me the hi & lo pressure values. Or, where to find the information. Thanks, Steve >Hi folk, >My 1998 5.0 V-8 AWD is in need of more freon. Could someone please tell me >the hi & lo pressure values. Or, where to find the information. >Thanks, >Steve It will vary some depending on the temperature. Usually you shoot for a low side pressure in the 30's and the high side will be somewhere between 150 and 250. You may need to "hot wire" the low pressure cutout switch while you are charging it to get steady pressure readings. >>Hi folk, >>My 1998 5.0 V-8 AWD is in need of more freon. Could someone please tell [quoted text clipped - 8 lines] > cutout switch while you are charging it to get steady pressure > readings. Thanks for your help Ashton. Steve > Hi folk, > My 1998 5.0 V-8 AWD is in need of more freon. Could someone please tell me > the hi & lo pressure values. Or, where to find the information. > Thanks, > Steve Trying to recharge an A/C system using gauges is a poor idea. The correct method is to pull a vacuum on the system and fill the system with the correct amount. The gauges are measuring the evaporator and condensor pressures, which are directly related to the temperature of these items. As long as their is enough refrigerant in the system so that there is liquid present at the orfice for the given external conditions, the gauges are going to reflect an evaporator temperature of 40 degrees, and a condensor temperature related to the outside temperature. All this is telling you is that you have the correct amount of refrigerant for that particuar set of operating parameters (engine speed, evaporator load, condensor load, etc.). You may or may not have enough refrigerant for another set of conditions. You may also over-charge the system. I learned this the hard way..... Ed >> Hi folk, >> My 1998 5.0 V-8 AWD is in need of more freon. Could someone please tell me [quoted text clipped - 17 lines] > >Ed If you look up the appropriate pressures for the ambient temp you can pin it down a little better then that. GM recommends just feeling the temp of the inlet and outlet of the evap to determine amount of charge. >>> Hi folk, >>> My 1998 5.0 V-8 AWD is in need of more freon. Could someone please tell [quoted text clipped - 21 lines] > If you look up the appropriate pressures for the ambient temp you can > pin it down a little better then that. A little better maybe - but the high side pressure is mostly dependent on the condensor temperature, which is heavily influenced by the ambient temperature and the amount of air being pulled through the condensor. Remember, there is a phase change happening in the condensor - the refrigerant is going from a hot gas to a hot liquid. Once you have enough refrigerant in the system to allow this to happen, the gauge readings are not going to tell you much more unless there is a blockage in the lines or unless the compressor is to weak. Once there is enough refrigerant in the system so that liquid is present at the orifice, the low side pressure is almost totally depndednt on the temeprature of the evaporator. > GM recommends just feeling the > temp of the inlet and outlet of the evap to determine amount of > charge. That is a quick test that will tell you that for the current conditions you have enough refrigerant so that liquid is present at the orifice. It tell you nothing about other conditions. Again - the only way to be sure you have the correct charge is to pull down the system and add the correct amount of refrigerant. Here is another GM diagnostic tip - Relative Temperature of High & Low Sides The high side of the system should be uniformly hot to the touch throughout. A difference in temperature will indicate a partial blockage of liquid or gas at this point. The low side of the system should be uniformly cool to the touch with no excessive sweating of the suction line or low side service valve. Excessive sweating or frosting of the low side service valve usually indicates an expansion valve is allowing an excessive amount of refrigerant into the evaporator. Ed |
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