Salinasjoelr
Active Member
Installing original air on my car that is a factory a/c car. Everything between the service manual and instructions from original air makes sense to me excluding these 2 parts location and how they are installed.
Original Air
- Thread starter Salinasjoelr
- Start date
-
I'll take a stab at the bottom Valve.
The way I understand AC in layman's terms:
The brass valve in your pic is the TXV, (Thermal EXpansion Valve). The curled end is the liquid filled sensor, it is placed externally near the evaporator (wrapped with duct sealer) and the liquid inside the sensor expands/contracts from Temps and opens/closes the Expansion Valve accordingly. It regulates opened and closed to prevent Evaporator Freeze up.
The TXV Provides the psi change which will drop the temperature of the freon.
There is a Temperature/Pressure relationship throughout the rest of the system:
The larger diameter freon lines are the Low PSI. (cool to the touch).
The smaller diameter freon lines are the High PSI side. (Warm to the touch).
Basically the compressor has to pump the freon and create a higher pressure, so the pressure can inevitably be dropped, via the TXV.
Note the larger openings of the Valve, it's placed in line on the low side, near the firewall, the evaporator is just on the other side, inside the car. The evaporator is a small unit that holds the ice cold, it acts like the heater core, waiting for the blower motor to blow the cold air around. When the cold leaves it, the TXV sends more low PSI freon to chill it down again.
The line on the other side of that Valve will be ice cold to the touch, when working properly.
The way I understand AC in layman's terms:
The brass valve in your pic is the TXV, (Thermal EXpansion Valve). The curled end is the liquid filled sensor, it is placed externally near the evaporator (wrapped with duct sealer) and the liquid inside the sensor expands/contracts from Temps and opens/closes the Expansion Valve accordingly. It regulates opened and closed to prevent Evaporator Freeze up.
The TXV Provides the psi change which will drop the temperature of the freon.
There is a Temperature/Pressure relationship throughout the rest of the system:
The larger diameter freon lines are the Low PSI. (cool to the touch).
The smaller diameter freon lines are the High PSI side. (Warm to the touch).
Basically the compressor has to pump the freon and create a higher pressure, so the pressure can inevitably be dropped, via the TXV.
Note the larger openings of the Valve, it's placed in line on the low side, near the firewall, the evaporator is just on the other side, inside the car. The evaporator is a small unit that holds the ice cold, it acts like the heater core, waiting for the blower motor to blow the cold air around. When the cold leaves it, the TXV sends more low PSI freon to chill it down again.
The line on the other side of that Valve will be ice cold to the touch, when working properly.
Last edited:
The top electrical switch looks like a cutoff, which will stop the electric to the compressor clutch, when pressure/Temps get out of range, ultimately stopping the compressor internally.
It also has the Thermal bulb for sensing temps.
Some Fabo member may have pics of an AC setup with locations of these parts.
It also has the Thermal bulb for sensing temps.
Some Fabo member may have pics of an AC setup with locations of these parts.
Last edited:
Demonic
Well-Known Member
Close. As my first instructor said many years ago, there's no such thing as cold, only the absence of heat. The evaporator gets it's name from what happens to the refrigerant inside, just like the condenser. If they called it a boiler, folks would get confused.
Hot air, from the return or outside, ( depending on the box duct ) transfers it's heat to the refrigerant in the evaporator in the heater/ac box ( which boils at a lower pressure, aka, evaporates from a low pressure liquid ). This low pressure vapor, containing heat, goes through the suction line to the compressor, which raised the pressure ( and temperature, and also adds it's own heat of compression ) so that the heat can be rejected, or transferred to the medium you have available, namely the front of the car on a summer day. In the condenser, the hot high pressure vapor is condensed, ideally back to a liquid. This high pressure, medium temp liquid then goes through an orifice/valve/capillary tube/TXV/EEV/float box valve ( some kind of pressure restriction, depending on weather it's a 'fridge, window shaker, Dodge Dart, or 1500 ton chiller ) where the pressure and temperature drops, and the much cooler liquid fills the evaporator ( but not completely, or you'd have flood-back ) then the cycle continues. The vapor compression cycle folks.
Hot air, from the return or outside, ( depending on the box duct ) transfers it's heat to the refrigerant in the evaporator in the heater/ac box ( which boils at a lower pressure, aka, evaporates from a low pressure liquid ). This low pressure vapor, containing heat, goes through the suction line to the compressor, which raised the pressure ( and temperature, and also adds it's own heat of compression ) so that the heat can be rejected, or transferred to the medium you have available, namely the front of the car on a summer day. In the condenser, the hot high pressure vapor is condensed, ideally back to a liquid. This high pressure, medium temp liquid then goes through an orifice/valve/capillary tube/TXV/EEV/float box valve ( some kind of pressure restriction, depending on weather it's a 'fridge, window shaker, Dodge Dart, or 1500 ton chiller ) where the pressure and temperature drops, and the much cooler liquid fills the evaporator ( but not completely, or you'd have flood-back ) then the cycle continues. The vapor compression cycle folks.
Demonic
Well-Known Member
Watch the aluminum threads carefully, a little light oil is your friend, along with new O rings.
67Dart273
Well-Known Member
WHAT YEAR MODEL are you working on?
The sensor on the TXV goes on the suction tube coming out of the evap "I'm not sure where" exactly, look over the evap and the tubing/ connections, look for tape/ insulation that has been removed/ cut.
The sensor tube for the switch is imbedded into the fins so to speak of the evap to sense evap temperature. There should be evidence of where it was.
The 69 Plymouth manual shows some models have a well (tube) into which you insert the TXV sensor tube
The sensor on the TXV goes on the suction tube coming out of the evap "I'm not sure where" exactly, look over the evap and the tubing/ connections, look for tape/ insulation that has been removed/ cut.
The sensor tube for the switch is imbedded into the fins so to speak of the evap to sense evap temperature. There should be evidence of where it was.
The 69 Plymouth manual shows some models have a well (tube) into which you insert the TXV sensor tube
Last edited:
Salinasjoelr
Active Member
All incredibly helpful. This is going on a 69 dart gt
BillGrissom
Well-Known Member
The green switch looks like the anti-ice switch in my 1984 M-B. GM used them too in 1970's. It opens to disable the AC clutch if the evaporator ices up. Rancor made many.
-
