Sorry to ask stupid question, but Mr. Hartwell, how do I find out what vehicle, year, rear A/C or no rear A/C? Am i missing something or should look at Hartwell profile page?
ASE Master since 1978, I have seen a lot of A/C issue like a drinking straw stuck in fresh air blend door or ink pen fell inside defrost vent on top of dash, then caught in "Mode Door" blocking its' movement. Newer models, will attempt 3 times to move back and forth to clear blockage. This system is common now starting in 2000 or so, but not older products.
Some a vacuum actuators while others use dumb motor, feed-back actuators or newer type, the HVAC control module counts the number of current signature signals as it "learns" what is means to be open or closed and anywhere in between. Plus, they typically use a TXV at the rear A/C while using an oriface tube on the front. Years, certain models, engineering put the oriface tube right on the EVAP inlet tube and when shut off, it sounded like hissing noise in glove box as system pressures equalized. They quickly started putting the oriface tube next to the radiator almost 3.5 feet from EVAP on high side of course, but solved noise issue and still worked. R12 or R134a going from high to low pressure makes it boil off creating cold air by condensing cabin moisture, but in the evaporator, it has the room to do this, some in the line, but it takes heat to boil it off. Slow the fan speed down, rev engine a little, the evaporator can flood, but boils off inside accumulator. The refrigerant hits a plastic cone and the dissicant and turns into vapor picking up oil in the bottom of the accumulator before being sucked into the compressor. Vehicles with TXV on the front (Only) evaporator core varies the amount of refrigerant go in. These systems use a high side receiver/dyer with the dissicant is located. If leak occurs, the TXV will adjust to allow more refrigerant in, keeping it cool until the last moment when it is so low, the pressure switch turns off the system to protect the compressor.
But how do I find which vehicle you have?
