Air conditioning questions....

[Rolling_Thunder]

Alright people - I need a brain check on some of my work...         I am by no means a A/C tech...          So here's the deal...   I have a Hot Rod Air kit which uses a set of vac solenoids to control the doors - I am trying to make the stock controls operate this unit...    so I have all the doors figured out - but my problem lies on another problem...             So here it goes...    and yes I have a factory service manual - but there is no clear description of what I need... 

1. The aftermarket kit uses a probe / knob adjustable thermostat to control the temp...     

2. The stock unit uses a probe that seems to attach to the heater control valve...    what the hell does this thing even do ?  I know it is supposed to keep the evap from icing up - but it seems to be non-operator controlled and controls the temp control valve to keep the unit from icing up....       I do not want to use the new knob adjustment

3. Does the heater control "slider" open and close the heater control valve to regulate the temp ?  My new tempo control valve is simply a open or closed valve that is Vac operated...    so this cable has nothing to attach to...       


So I need to know the function and connection points of the "Sensing Unit" - I know it mounts to the Evap box and the other end connects to the temp control valve...    What does this thing do? and how can I adapt this unit to my new box ?   

I have thought that if I purchase a cable operated heater control valve I can use the stock temp "slider" -  the only issue I would then worry about is the manual thermostat - can I somehow adapt the stock sensing unit to take the place of the newer crap ?


If someone can understand what I'm asking I would be much appreciative of some advice....    This is currently the only thing holding up my project.   

[elacruze]

 

I'm very interested. I'll be using a Classic Auto Air kit;

http://www.classicautoair.com/MOPAR_OEM_Parts_Engine.html

I don't have the hands-on with my own stock A/C bits to know where they all attach, but I do know A/C.
IIRC there is no temperature control, that is some control unit that maintains a set temp on the stock unit. Most 'old cars' just bleed in heat from the engine coolant to moderate the temperature you feel. What you're seeing in the evaporator is probably the bulb for the TXV, or thermal expansion valve. The TXV modulates the volume of refrigerant entering the evaporator to keep the evap. temp at a constant temperature, usually about 35*F.
The aftermarket unit, if it has a thermometer probe for cabin temperature, probably just has a thermostat which controls the compressor circuit.

[John_Kunkel]

Many auto A/C systems use the compressor clutch to control the evaporator temperature, it gets too cold and the clutch disengages the compressor. Mopar didn't use this, they placed an Evaporator Pressure Regulator (EPR) in the compressor suction port and the clutch remained engaged unless there is low pressure at the drier. The refrigerant expansion valve has a capillary bulb that inserts into the evaporator fins and senses the evaporator temperature, it then opens/closes to control the evaporator temperature. The A/C heater water valve has a similar capillary inserted into the heater core to sense its temperature, non-A/C cars use a blend door to control the heater temperature.

Most aftermarket A/C units use the capillary in the evaporator hooked to a switch to control the compressor clutch so it can easily be wired into the original wire from the control to the compressor. The A/C diagrams in the FSM might help in trying to hook the original control to the aftermarket unit or...it might not be possible.  

[Rolling_Thunder]

Alright...       So I figured it out - I think...    the Thermostat that uses a capilary tube in my NEW A/C box regulates the temp (adjusts the heat range as well as activates the A/C compressor when the knob is turned to a certain point...       The A/C compressor can be hooked to the factory controls without issue...     and the stock A/C controls can be used to open and close the heater control valve....     So why would I need this adjustable thermostat ?    

This is what comes in the Kit....    it is merely connected to the compressor clutch and a 12V source...   -  so If this function is going to be controlled by my original controls why do I even need this thermostat ?
 
http://www.hotrodair.com/index.cfm/page/ptype=product/product_id=170/category_id=23/home_id=2/mode=prod/prd170.htm  



This is the only thing I have not figured out yet...     I have everything else good to go...        

I also have a question - I was told if I left the temp control to as cold as possible it could potentially ice up the evaperator...   what is the result of this ?  whouldnt the ice just thaw and drain out of the box through the drain tube ?