Under dash A/C unit

Cbumpus9398 · Post by **Cbumpus9398** » Fri Mar 13, 2015 8:18 am

I am finally ready to install the unit from making a new heater core and finding and replacing the expansion valve and thermostat switch. It funny how after your first time, you become an expert on that particular model. What I need now is to know what that black wrap is around the expansion valve and connections. The old wrap is brittle and I need a new piece. What is it and why is it needed? Thanks Charlie

Cbumpus9398 · Post by **Cbumpus9398** » Sat Mar 14, 2015 6:52 pm

Does anyone know how the A/C system works? I finally have it all intalled but I can't get the compressor to come on. Heater works great but not I can't get the A/C compressor to come on. This is in my 1972 with add-on under dash unit. Everything is original.

sargentrs · Post by **sargentrs** » Sun Mar 15, 2015 9:07 am

Only got a minute. Verify your wiring first http://www.fordification.com/tech/wirin ... g_69ac.jpg

Cbumpus9398 · Post by **Cbumpus9398** » Sun Mar 15, 2015 9:26 am

Wiring is right. The only thing is I don't think the limit switch is working. Before I removed the unit this switch was bypassed and the compressor came on. I still bypassed but the compressor won't come on. I have replaced the expansion valve bc it was broken. I installed it just like it was. Idk

Mach428 · Post by **Mach428** » Mon Mar 16, 2015 6:51 am

First things first. The wrap around your expansion valve is to insulate against heat. You can buy replacement wrap at most auto parts stores.

Second, you will need to use a 12V test light and see if you have current at the compressor when the AC is on. If so, the clutch is most likely bad. If not, you will need to trace the wires going back to the evaporator assembly switches inside the cab. The "limit" switch that you mention is to insure against the evaporator freezing up. Equally, there is a switch that engergizes the compressor when the control lever on your dash is placed in the AC position and the temperature control is moved to COLD.

This sounds complicated but it really isn't. A test light inside your cab will work wonders to see IF you have power going to all of these switches and if so, which one is not allowing power through.

Hope this helps.

fireguywtc · Post by **fireguywtc** » Sun Mar 22, 2015 10:24 pm

There is a lever switch that pushes a black button on top of the AC unit where the glove box would be. I would check that switch as it gave me some fits on my truck. I had to move the slide control on mine to get it to activate when I would first turn it on. Also the temp/cycle control switch that moves with the temp slider my give you some grief also.

Cbumpus9398 · Post by **Cbumpus9398** » Mon Mar 23, 2015 6:12 am

That lever switch you speak about May be the trouble. When I bought this truck it was unplugged and the two wires were plugged into each other as if thay were trying to bypass the switch. But, even bypassing the switch, it worked before I had to make a heater core replacement. I just don't know, I didn't do anything that would make this not work. All I did was unplug and then plug back up. Thanks

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