First Post!! Help

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JohnHere
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Joined: Sun May 13, 2018 10:20 am
Location: South Carolina Upstate - USA

Re: First Post!! Help

Postby JohnHere » Sun May 24, 2020 7:33 am

A few additional thoughts. Are you the original owner of this vehicle, and do you know whether the system has been serviced previously?

Also, Al9 brought up an interesting point about the state of the charge. If you haven't already done so, I suggest having the refrigerant recovered and weighed to determine what's actually in there now. After 15 years, it's probably low if it has never been serviced, possibly resulting in the issues you're experiencing.
Al9
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Joined: Tue Mar 10, 2020 3:26 am

Re: First Post!! Help

Postby Al9 » Mon May 25, 2020 2:06 am

Proper refrigerant charge is really critical with these compressors. The TXV is set up to keep a stable refrigerant flow through the evaporator even at really low heat loads, at the cost of losing energy efficiency due to letting the compressor pump denser wet (that is, in saturated state) refrigerant; this is meant, among other things, to allow the control mechanism to reliably divert enough refrigerant to the crankcase so to keep the pumping displacement finely tuned, at any heat load. Not enough refrigerant flowing through the system, either due to a TXV "not opening enough" malfunction or due to a low charge, and the compressor displacement control basically goes haywire, even though the control valve is constantly trying to keep it into low displacement due to the really low suction pressures it is sensing.

EDIT: Just ran mine. Cold engine, 72F dry weather, car parked in the shade, new condenser, engine idling at about 800 rpm, cooking thermometer in center front vent, heater door closed, air set to front vents, recirculation door open halfway, driver side door open, hood closed, blower fan speed one notch less than maximum. Turn AC on, the compressor clutch immediately engages and the condenser fan takes 10 seconds to turn on. During these 10 seconds, vent temperature is ambient and you can feel the engine progressively bogging down as the compressor is building pressure up. Then as soon as the condenser fan turns on vent temperature starts going down. About another 10 seconds and vent temperature is a stable 41F. Hand holding the thermometer starts getting numb due to the cold. (as a side note i remember it giving cold air even faster than that in the past and i'm trying to get a replacement TXV, i think the original one likely lost some spring tension over time influencing how fast it pulls suction pressure down)

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