Anyone converted 4.0L from R12 to R134a?

It's always a very good idea to throughly pump down a system if you are changing the refrigerant.

Is it possible that your gage is measuring the high side instead of the low side? And you did open the valves right? I don't mean to be insulting but speaking for myself I've had more trouble overlooking the stupidest things that were obvious in retrospect.

I don't recommend this but I installed AC on a vehicle that didn't have it before, and used a factory evaporator designed for R12 with a modern compressor (along with new everything else). This being a new install it was of course full of air at normally air pressure. Not having the proper equipment to pump it down and then put in just the right amount of refrigerant (and just how much R-134a does a non stock AC unit in a Studebaker take anyway?!) I started putting refrigerant in until the unit was blowing cold and the gage was in the green, worked just fine.

Good luck!

Jeff DeWitt

You need to evacuate all the air from the system, using a vacuum pump, like this one.

There should be a valve core inside the original low side port. Perhaps you have the wrong valve core removal tool.

Earle

More than that a necessity. Venturi type pumps will not get them down enough by themselves.

No two A/C installs take exactly the same amount.

Hi Sam,

It would be nice if you can vacuum the system before adding R134a, yet, it is not critical. From my last 2 years' experience, It will still work. The reason that you have a high pressure reading might be due to the compressor is not engaging. This is the case for one of my 93 ZJs. In my case, the compressor side electric cable (factory taped to the positive cable from the battery) was not plugged fully into the compressor.

Good Luck

Paul

P.S. The cable connector might be partially unplugged when one replace/disconnect the battery.

I did not open any valves. I was expecting a needle valve in the low side port fitting, but cannot find it. I noticed the fitting also has a 1/4 inch square type lug coming out at 90 deg angle. Is that the valve you are talking about. I'm a rookie when it comes to AC systems!

Sam

Jeff DeWitt wrote:

You need to pump the system down to get all the R12, moisture and air out of it. You should replace the oil with a R134a compatible oil, either PAG or ester. O-rings designed to handle R12 cannot really handle R134a and the higher pressures and temperatures that come with it. These parts are all cheap, but you have to open the system to the air in order to replace them.

Sure you can do a half-assed job, and the system will work after you charge it up. But if you do a good job it will still be working years down the road.

With regard to the valve, it is possible that you have a manual valve in the low side port, rather than a Schraeder valve. Do you have a digital camera?

Earle

I made some progress today. Turns out that my compressor does not have a Schrader valve in the low pressure fitting. It just has a manual valve. Hopefully by this time tomorrow, I'll have some colder air blowing in my Jeep!

Sam

snipped-for-privacy@hotmail.com wrote:

I just recharged my old grand wagoneer. There were no schrader valves. You have to hook up the freon can, then turn the valve on the compressor fitting (its at 90 degrees) to open the port to the fitting. You only turn the valve so it is in the middlle of its travel. There is also a valve on the high side port on mine. If you turn the valves all the way from where they were, you isolate the compressor. This is needed for something sometimes according to the manual. I had a leak at the sight glass on mine. Freon was coming out as fast as I was putting it in. Tightening the connections around the sight glass fixed that.

Fred

Sam.

There's valves on the compressor for the high and low sides. they're under the thin metal caps. At least on a 89 XJ I converted. It worked for me and was working over a year later when I sold it. The system was empty so I pulled a vacume on it for several hours and filled it.

JoBo