does any one know the tread size on the low side of the line. mine is rusted and thought cleaning it up with a die might let me get my guages on it so i can put more freon back in.... its still the r12 system mabe even the thred size for the guages would help....thanks in advance

 

On R12 low and high are the same. I believe it's a standard 5/16" flare with a shrader valve in it.

 

Standard hose sets for R-12 are 1/4" flare.

Automotive fittings will be 1/4" flare on the suction side and most of the later vehicles up to the introduction of R-134a will have 3/16" discharge requiring you to install a 3/16" X 1/4" adapter to use your hose set.

Here is the 1/4" flare on the suction side.



And this is the discharge side, you can see the adapter screwed on to the fitting, there is a valve core inside to actuate the schrader valve.

I leave mine on permanently and secure it using a o-ringed threaded cap

They were installed to protect the untrained person from trying to charge the system through the discharge port and having the can explode in their hands.

You can get these adapters at Auto Zone or on line.



If you have R-134a you can get adapters that convert your 1/4" hose set to the special Acme thread snap on adapters, I have an expensive set for my gauge manifold, but the gauge is still not calibrated for 134a


Jim

 

On my 1990 the suction connection is 1/4", but the discharge connection is 3/16".
I just purchased the 3/16" to 1/4" adapter which was around 23 dollars with tax.