ac drier question

[dcruz]

Guys, I have a 1978 280z that i'm having trouble charging with r-12, It has all the original components but it won't charge up. The low side won't go pass 15 psi and the high side starts to climb all the way up. Last night I was checking out the system and noticed that the ac drier has a some type of sensor. I don't know what this sensor is and where it should connect to, my drier has the sensor on it but the cables seem to be broken off, Can some one please tell me what this sensor is? Thanks

[sblake01]

That sensor is the pressure swicth. Should be a two wire plug with a yellow wire and a yellow/red stripe wire. One wire goes to the AC relay and the other to the thermostatic switch that senses evaporator temperature. The pressure problem you are describng can be caused by excessive moisture in the system. Sometimes evacuating the sytem and pulling a good vacuum on it will cure it but most of the time, you have to replace the drier.

Edited September 28, 2011 by sblake01

[dcruz]

sblake, thanks for the quick response, well my pressure switch isn't connected to anything, the ac did blow a bit cold but I tried to add some more r-12 and made it worst, now it won't blow cold at all. sblake if the pressure swithc aint working or isn't connected can I still charge the system? Thanks

[Mike W]

dcruz,

I have a 75 260Z that came with factory air but stopped working many years ago due to a leak in the condensor. When I rebuilt my engine the first time (again many years ago) I removed many of the non functional AC components such as the compressor and as much tubing as I could, but left some of the tubing and the dryer in the car as I was unable to get the connections loose. I'm now in the process of doing some work on my engine compartment to clean it up and used some Kroil penetrating oil on those connections and was able to romove all of the left over AC components including the dryer. Mine has not been used for many years and I do not even know if it is the same one as on your 78, but ironically I live in Austin as well and would be willing to let you take this to see if it solves your problem. The one I have does have a 2 pin connector on it and so it may be the same one as in your car.

If you are interested, send me a PM and we can figure out a way to hook up. Might be fun to share some Z stories as well.

Mike.

[ZCurves]

dcruz - adding to what sblake has already mentioned... I believe that you have a blockage at the Drier or at the Expansion Valve. This is why you have 15 Low and pegged out High. The ratio should be 10:1 (H:L), so you should be looking at 150:15, 200:20, etc. If the Pressure Sensor is broken off or non-functioning, then the compressor would not engage and you would have nothing. Follow sblakes advice and replace the Drier with a NEW one. Never reuse a Drier or use one that has been exposed to the atmosphere for an extended period of time because they absorb moisture and loose their effectiveness. Put a real hard vacuum (-30hg) on the system for like a hour.

When you order a Drier, make sure to get a new Pressure Switch, -together these should not be over $65. Be prepared to 'short' the connector for the Pressure Switch until you get the first can of R12 into the system. This should be 'Liquid' or upside down on the tap, the remaining should be gas or right side up on the tap. Be sure to watch your ratios! Good luck.

[Willoughby Z]

See page 2...

http://www.classiczcars.com/forums/showthread.php?39425-AC-Expansion-Valve-Repair-and-Setting