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My Moms 93 Eldorado


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Here is the AC info I said I was going to post. It puts it all in a nut shell, after reading it one understands a great deal about the AC system. I hope no one gets mad it's so big.--- I had to learn how to use the OCR in my scanner software, sorry it took a wile........... DESCRIPTION Temperature Control Switch A thermostat switch senses the temperature of the evaporator and engages or disengages the compressor clutch, The control for this switch is located in the cab. Compressor The compressor is designed to compress vapour and can be damaged by non-compressibles such as dirt, moisture, liquid refrigerant (R-134a), etc. The compressor draws vaporized R-134a from the evaporator (which maintains the Idw pressure necessary for proper evaporation) and compresses the vapour to a high pressure, which is necessary for condensation. The high pressure vapour then moves into the condenser where heat can be radiated to change the R-134a back to liquid. Note: R-134a designates the type of refrigerant used in heavy duty vehicle air conditioning systems^

Coniyressor Drive Cljutch The R^34a compressor s^tejris use an electronically actuateff'cluteh to engage and^disengage drive to the compressor. The 'V' belt pujiey is mounted on a bearing and is free to rotate without turning the compressor crankshaft any time electrical power is disconnected. The compressor is not operating when the pulley is freewheeling. The field coil is energized by; supplying electrical current to the exposed wjj^Jg^^ of the coil winding is grounded to^lC^^Wfetessor and equipment frame. Energizing the coil creates a magnetic farce that locks the driven disk to the pulley and drives (e compressor. Condenser The purpose of the condenser is to radiate enough heat energy from the compressed high pressure vaporized R-134a so that the R-134a changes from vapour to liquid. During normal operation all the high pressure section of the system will be warm or hot, but large quantities of heat should be radiating from the condenser. Nothing should be permitted to stop or

SM 2021 6-00



QperatorsCgmpartment • Air Conditioning

Section 260-0130 slow down this radiation of heat. Cooling fins are located on the condenser tubes and fans are used to circulate cool air around the condenser tubes. Keep all 'eaves, paper, dirt, etc. clear from the condenser and condenser filter. The cooling tins should be strasght to permit tree flow of air. The condenser is sometimes located ahead of the engine radiator and blockage ot air flow through the radiator also affects tne condenser. Bent fan blades, slipping fan drive, inoperable condenser fan motors, or any other fault that lessens the amount of cool air circulated through the condenser, should be corrected. The oil, dirt, or antifreeze will act as an insulator that will inhibit the radiation of heat. Since the purpose of the condenser is to radiate heat energy,«anytning that prevents or inhibits this action may affect cooling, but the temperature and pressure of the R-134a raise and lower together. Heat energy that has not been radiated will remain in the R-134a and the result will be pressure that is too high. The condenser, hoses, connections and seals can be damaged by the high pressure. Pressure sensing safety switches may be activated by the high pressure caused by the condenser not radiating enough heat. Receiver Drier The high pressure liquid R-134a moves from the condenser to the receiver drier, where the R-134a is stored and filtered. Moisture ir, the major enemy of the air conditioning system and the desiccant inside the receiver drier will absorb only a small amount. The container of desiccant inside the receiver drier may break open and contaminate the system if any attempt is made to dry the desiccant, or, if more moisture is inside the system than the desiccant can absorb.

Every effort should be made to remove all moisture from the system and install a new receiver drier if its condition is questionable. Installation of a new receiver drier is recommended each time any part of the R-134a system is open to the atmosphere.

Bubbles are observed in the sight glass on top of the receiver drier during the charging procedure.

A filter screen is located in the receiver drier to stop solid contaminates from leaving the unit. Blockage of

the fitter will result in a drop in pressure that will be indicated by a drop in temperature. Connections of the new receiver drier should be securely capped before installation to prevent the entrance of moisture (air) while in storage. Thermostatic Expansion Valve An expansion valve is installed in the system to lower the pressure before the R-134a enters the evaporator. The reduction in pressure is done by passing the R-134a through a small hole (orifice). The size of the orifice must be controlled to compensate for changes in pressure and temperature. The temperature of R-134a leaving the evaporator is sensed by a thermostatic sensor that moves the valve seat via a diaphragm and actuating pin. Evaporator - Heat/Cool The evaporator is the low pressure, low temperature component where liquid R-134a absorbs heat from surrounding air. The expansion valve bleeds high pressure R-134a into the low-pressure evaporator. The R-134a expands rapidly in the evaporator and its temperature is quickly reduced. The R-134a absorbs heat from the air when the blower fan circulates air over the evaporator coil fins. The exchange of heat from the air to the R-134a depends upon the difference in temperature. During high heat load, such as usually encountered when the system is first turned on, the temperature difference is great and the

R-134a will absorb heat quickly. The blower fan can be set at its highest setting to circulate large quantities of warm air around the evaporator. After the cab has cooled, the fan speed should be reduced so that the already cool air will have a longer time to yield heat to the R-134a as it passes the evaporator coils. The heater circuits utilize engine coolant at approximately 82° C (180° F).

High Pressure and Low Pressure Switches

The pressure switches are electric switches that monitor air conditioner operation. The high pressure and low pressure switches are activated at preset pressures and engage and disengage the compressor clutch.

SM 2021 6-00

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I just had a phone call from my folks and they werevery happy with the car. They said it's 93 outside and they were out with two friends in the Eldorado visiting friends this after noon. They say the cars AC was working very good, it was nice and cool in the car. I think that's pretty good since there were four adults in the car and it is so hot and humid out side. I hope it holds up for them. I got lucky getting it to work. I never mentions my cars AC on the ride up yesterday. The trip is part hi way and part slow traffic for a wile on another main road getting to there home. I saw 94 outside temp and my engine was at 218 with the AC on in traffic. On the hi way it was running at 209 with the AC on. I think that is very good. Later Guys....

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