A/C update Question (For stock unit)

[TRIPLE-GREEN]

Ok, as many of you already know I have a 1973 Challenger. I have a stock 318 with the original A/C unit. I was told by my parents before taking delivery of the car that the A/C was checked and everything was worked (2 years ago). But it I never used it and when I checked out out blew hot air. I wanted to know what can one do to bring the A/c unit up to working while maintaining as much of the original system as possable. I think there may be a leak. But once I get the leak fixed I worry I can't have it refilled and charged. Due to freon being different now.
   I was told by a local, if I change the dryer and the "trunary" (Not sure how to spell that) switch I can have modern Freon added and get it working again. Any tips?

[quagmire]

Yes, the trinary switch and the dryer will have to be replaced along with installing conversion charge ports.  The refrigerant oil will also have to be changed, R134a and R12 use  different oils that are not compatible with each other.  These would be the absolute bare minimum things required to convert it.  Ideally all of the seals should be changed along with the rubber hoses being replaced with barrier hoses.  A larger condenser would also help, R134a operates at higher pressures so the stock condenser may not be ideal.  This is also the reason the pressure switch needs to be changed. 

[TRIPLE-GREEN]

So i can use the stock  pump and box? That is great. I can easly change the rest. YEA!! 

[quagmire]

Yeah, you should be ok. Just make absolutely sure you drain all of the old oil out and use a PAG or Ester oil. PAG is 134a only, Ester is compatible with both types. If you dont change the seals and gaskets in the compressor too you may develop a leak.  In reality I've seen many people do the bare minimum during conversions and never have any serious issues.  So oil, pressure switch, charge fittings, and a dryer minimum.  Seals, hoses, and the condenser if you are doing it properly.  Also remember that you will charge it with only 80% of the systems capacity when it had R12.

[ShelbyDogg]

I've converted lots of cars over to 134 freon. Get a $30 conversion kit from WalMart. Off season it sometimes sell for $25.  Auto Zone las a  "loan a tool" Vacuum pump.  Vacuum your system for 30 minutes, then close it off and watch the guages an hour later for lost vacuum.  If the vacuum is still there, fill it with the conversion oil first then start it up then start adding the freon.  If your system was sealed up from 2 years ago and still has pressure in it. The drier is probably still good.  For $25, it's worth a try. 

I have my 72 Cuda charged with 134a and all stock stuff.  It's COLD. 

[TRIPLE-GREEN]

I noticed somethng today that might be my problem. I turned the a/c on while I was looking at the compressor. The flat plate at the front of the compresser didn't move. Is it suppost to? How do I know if my A/C compressore clutch is working? Again a mechanic 2-3 years ago said the system worked. Not saying that might be my only problem but I would like to know if I have a working A/C clutch. If the cluch is not kicking on that might be a problem.   

[ShelbyDogg]

I noticed somethng today that might be my problem. I turned the a/c on while I was looking at the compressor. The flat plate at the front of the compresser didn't move. Is it suppost to? How do I know if my A/C compressore clutch is working? Again a mechanic 2-3 years ago said the system worked. Not saying that might be my only problem but I would like to know if I have a working A/C clutch. If the cluch is not kicking on that might be a problem.   

The clutch coil is hooked in series to a low pressure switch on your drier. follow the blue wire to the connector and you'll see the switch. Turn on the a/c again and use a test light on the clutch wire, to the connector, then to the connector on the switch. You'll probably notice 12v on the supply side and not on the clutch side.   Hook up a can of freon and the clutch will start spinning.  Before you do that, you might as well get a set of  those green A/C o-rings from AutoZone and change all of the o-rings at all of the tube junctions because the freon went somewhere. When you charge it up with 134a, get a can of Dye-Check Freon at WalMart and add it too.  Buy a black light bulb at Walmart for $2, Then if your system leaks, the leak will glow green with the light.

[TRIPLE-GREEN]