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Discussion Starter #1
I have a 67 Mustang 289 auto base model.
Previous owner had after market under dash AC installed and it is from Old Air Products. All parts are from Old Air. Have owned it since November and just finished some repairs.
The AC ran cold when I purchased it but did not use it through the winter. Yesterday I turned the AC on and heard the compressor click on. AC air was in the mid 70's and outside air 90. Guessing there is a small leak and it leaked down over the 6 months I did not use it.
Today the compressor will not turn on. Blower works fine. Looked for fuses and found a 30 map. Pulled it and blower shut off so I know the fuse is good. High pressure line get hot but low pressure runs cool and not cold.
I had a 134a charge cylinder with hose that fit the low pressure line on my Impala but that same connection will not fit on the Mustang. The connection port on the low pressure hose AC line does not fit the charge cylinder connection. Pushed as hard as I could but will not seal. Seems that the AC line charge port ribs may be further back and will not connect to the charge cylinder.
Any ideas? Are there adapters I can use?
 

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I assume the A/C system that was installed in your car is a 134a system. The High and Low pressure ports are different sizes to prevent anybody from connecting a charge hose to the High pressure side. And those fittings have a standard size. Are you trying to connect your charge hose to the High pressure side?
 

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It might be worthwhile investing in a refrigeration kit that comes with a vacuum pump and leak detector. Are you sure the system is 134a rather than R12? it is my understanding that the two refrigerants have different sized service port fittings. Does your system have a trinary or binary switch? I would first investigate why the compressor isn't engaging. I would check all fittings and use a refrigerant leak detector. If you find the source of the leak and fix, I would recommend using a vacuum pump prior to charging. Let the system sit overnight to confirm all connections are good prior to charging. I would definitely contact Old Air for any recommendations as you might need to re oil your compressor. They might even recommend replacing the drier if the closed system has been contaminated.

Refrigeration Kit with Vacuum
 

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I have an Old Air Products set-up. A few comments:
-Like said upthread, the high and low side of my 134A system are different sizes, and they are "standard". I borrowed manifold gauges from O'Reilly's and all of them fit the ports. The stems are not standard, though. So while the connection is standard, the design is special. (As I recall, there are some things like o-rings on the stems that aid in sealing.)

-There is a low pressure safety switch that should be wired in between the compressor wire and the thermostat wire. This prevents the clutch from engaging, preventing the compressor from turning if your system is low on pressure. If your system is sufficiently charged, make sure that it is wired-in. If disconnected, the clutch won't engage.

-It's a holiday weekend, but on Tuesday, give OAP a call. I've found them to be very responsive and helpful. I suggest you grab what identification items that you can before calling. My compressor has stamped numbers. I think they can trace this back to what system/vintage that you might have.
 

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Discussion Starter #5 (Edited)
Compressor says it is 134a

Possible that the connector on the Freon charge kit,plastic, is damaged and won't snap on. High and low pressure charge ports have different sizes.
I have binary a switch and I have made sure it is seated. Disconnected and reinstalled it with no results. Tested connector with a light and power is going to the switch mounted on the AC line.
I am aware that R12 has different ports. They screw directly to hoses.. 134a has snap on connectors and threaded internals.
I have ordered manifold gauge and hoses and leak detector.
 

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Discussion Starter #6 (Edited)
Mystery solved. The charge port is horizontal and hard to see. I found a piece of black broken plastic screwed into it. With a small screwdriver I was able to unscrew it and the Freon cylinder snapped onto it and the gauge showed a full charge. That piece broke of the black screw on cover. Compressor will still not engage. Will call manufacturer to see what they say.
I jumpered the female end that goes to the binary switch and also ran wire from battery to AC wire to compressor. Both times it started and blew cold air. Ordered to binary switch from EBay
 
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