My rear AC system on my 03 Expedition is not blowing cold...the front is fine however. I am thinking that there is a relay or electrical valve of some sort that tells the system to let the coolant into the rear area. Does anyone have a wiring diagram or idea on where to look for that?

Thanks!
DAve

 

I looked in the manual and it has this kind of valve. If this is the problem, you are going to have to get a refrigeration guy to look at it. You could try www.helminc.com for a wiring diagram, but my impression is the electrical just controls the blower and some remote air doors in the rear unit.

Thermostatic Expansion Valve

The thermostatic expansion valve (TXV) restricts the flow of refrigerant from the high pressure side of the refrigerant system and separates the low pressure and high pressure sides of the auxiliary refrigerant system. Refrigerant entering and exiting the auxiliary evaporator core passes through the TXV through two separate flow paths. An internal temperature sensing bulb senses the temperature of the refrigerant flowing out of the evaporator core and adjusts an internal pin-type valve to meter the refrigerant flow into the evaporator core. The internal pin-type valve decreases the amount of refrigerant entering the evaporator core at lower temperatures, and increases the amount of refrigerant entering the evaporator core at higher temperatures.

 

WHere is that valve located?

 

Thermostatic Expansion Valve



Removal and Installation

Recover the refrigerant. For additional information, refer to Section 412-00
.
Remove the RH quarter trim panel. For additional information, refer to Section 501-05
.
Disconnect the fittings and remove the thermostatic expansion valve.

Discard the O-ring seals.

To install, reverse the removal procedure.

Install new O-ring seals lubricated in clean PAG oil.

Lubricate the refrigerant system with the correct amount of clean PAG oil. For additional information, refer to Section 412-00 .

Evacuate, leak test and charge the refrigerant system. For additional information, refer to Section 412-00 .


It's a square looking metal box with 4 refrigerant lines going to it.

 

Thanks, Is it an electrical type valve or mechanical? From the online research and the info you gave it sounds like if the valve is stuck closed it could keep refridgerant from entering the system to cool the air...I wonder if it is stuck and I give it a tap if it will "open" up?


Thanks again!
Dave

 

mechanical Not likely
Most of the time it will lose its charge on its remote sensing device and quit. They are kind of like a thermocouple on furnace. It has bulb full of something and when it loses it, it's kaput.

 

If it has what subford is talking about, it will have a very small tube coming out of the valve, that curls over and disappears behind some insulation. Like he said, it will have a bulb under the insulation, and when the fluid expands and contracts in the bulb, it will move in the small tube and open the valve.

They must control the refrigerant in the front by turning the compressor on and off, and control the rear with this valve. I know enough about refrigeration just to be dangerous.

 

Interesting, well I'll take a look....thanks a lot for all the help!

Dave