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A/C controls

Posted: Thu Jan 21, 2021 8:32 pm
by ZAKsPop
Hi everyone. I'm new here and a complete novice when it comes to A/C. I know the physics behind how it works but not all of the intricacies of an A/C system. My question is about the controls. I have an aftermarket A/C system built by Classic Auto Air for my classic car. It comes with a control that fits the car perfectly if I were keeping the original dash. However, I am retro rodding this car and the control it comes with isn't up to par with my plans. I am modernizing the interior and I am wondering if I can use an A/C control from a modern car with the kit. Thanks in advanced and thanks for your expertise.

Re: A/C controls

Posted: Fri Jan 22, 2021 7:21 am
by Cusser
I would think that there are modern controls that could work. Some modern systems work by pressures, some might work using electronics. I believe most systems once "on" have the driver "add heat" to make the temperature comfortable.

Systems like in my '88 Mazda truck and '98 and 2004 Frontiers work using a temperature sender in the evaporator fins. When evaporator temperature gets close to freezing temperature of water, it shuts off the compressor, then turns it on again once temperature rises a few degrees.

Re: A/C controls

Posted: Fri Jan 22, 2021 2:46 pm
by Al9
Cusser is right, with fixed displacement compressors automatic temperature control (that kind of AC where you set the interior temperature you want in digits) is accomplished by adding heat and/or regulating blower speed and/or air recirculation percentage. Regulating interior temperature by directly controlling how often the compressor clutch cycles (i.e. cycling it off once the desired cabin temp is met, then cycling it on again shortly after) will likely result in serious compressor/compressor clutch wear, with an auto sized AC system.

I believe there's simply too much engineering behind ATC to be able to adapt a climate control unit recovered from another car without serious issues.

If ATC is what you mean with A/C control from a modern car, then i think a good way to start would be some kind of electronic thermostat that opens and closes a solenoid valve that feeds coolant to the heater core, with enough hysteresis (what Cusser means with the compressor turning back on once the evap fin temperature rises a few degrees; those few degrees are the hysteresis, and they avoid excessive compressor cycling related wear), and a temp sender located somewhere in the interior away from the sun.

Re: A/C controls

Posted: Fri Jan 22, 2021 4:42 pm
by ZAKsPop
Hmmm. I am totally lost reading all of that. I was hoping to put a late model A/C control in but I guess that isn't going to happen. Looks like a custom control from them.

Re: A/C controls

Posted: Sat Jan 23, 2021 6:24 am
by B52bombardier1
I have a system from Classic in my 70 El Camino with the controls in the dashboard. Hide the Classic temperature and operation controls somewhere else. They are not large, don't need vacuum and are stash-able someplace. Think glove box or maybe under the drivers seat.

For money, I bet that Classic would make you a wiring harness of any length that you need.


Re: A/C controls

Posted: Fri Apr 30, 2021 11:20 pm
by chrstopher007
You can follow the below steps
Step 1: Refrigerant in a gas form is compressed by the A/C compressor which runs off a belt, compressing the gas into a high-pressure state
Step 2: This refrigerant then enters a condenser – a heat exchanger normally placed in front of the radiator - where it changes state into a liquid
Step 3: The refrigerant then enters a dryer where most of the moisture is removed from the liquid
Step 4: The liquid is then pumped through an orifice tube which takes the refrigerant from high pressure to low pressure, changing its state into a cold gas
Step 5: The cold refrigerant in its gas state then flows through an evaporator. The evaporator then works as a cross-flow heat exchanger, cooling air that is passed through the heat exchanger fins by an A/C fan and finally blown through and into the cabin