This is an ancient thread and I know a BUNCH more about converted a/c's now than I did then.

There is no way I would attempt to charge an R12 system converted to 134 without monitoring the high side gauges. Also you should never attempt to charge liquid on anything. You can get by with it sometimes, but it is a risky practice due to potential compressor damage.

Have a great day,

I did my charging with the can upright, so as to charge in gaseous form, and kept it in a bowl of warm water to keep the can from getting cold. I did buy a full set of gauges, I just didn't know where the high-side port was at first. Later yesterday I found it and hooked it up (after the car had cooled down). I turned it on and set the AC to full blast, with both high- and low-side gauges hooked up. At idle, and with the AC on, I read about 25psi low side and about 205 high side, and they fluctuated a little. The engine shook like crazy while the AC was on, and it blew hot air. I noticed that the low pressure tube going to the compressor (with the low-side port on it) had condensation on it, and it was very cold to the touch. When I turn the AC off the engine resumes its smooth idle.

When I started this job yesterday morning, the low side pressure was 0 psi and I put in 24oz of r-134a. I did not add any oil (the retrofit sticker indicates ester oil was used). If it means anything, the high-side port didn't have a new fitting installed - I had to put one on myself.

I did some more research and found a few clues:
shaking engine suggests broken compressor blade or stuck clutch
hot air suggests broken evaporator
Are these right? If so, I'm going to just use my windows for air conditioning.

Arash

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'82 300TD
'77 6.9
'75 280S
'74 280
'87 Porsche 944 turbo

With 25 low side and 205 high side, plus a cold return line to the compressor, I'd say your charge is okay, the evaporator is okay, and the a/c system is functioning. The question remains why you don't get cold air from the vents. I believe the problem lies in the dashboard. I can't comment more specifically than that.

Lack of a proper r134 service port on the high side suggests a poor backyard retrofit. One can only wonder what other shortcuts were taken.

It would be wise to have UV dye added to the system at this point. We don't know for how long the charge will last. If it does leak out, the UV dye will tell you where the leak is. If it's the evaporator, you'll find dye in the evaporator condensate (water puddle on the floor).

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95 E320 Cabriolet, 159K

Kestas is correct about the a/c portion running okay, or at least refrigerating. You need to check your monovalve. It is on the firewall near the battery and has four screws on top. With engine cold, remove the four screws and lift up the top. If it is flooded with coolant above the diaphragm, get a rebuild kit and replace the diaphragm and plunger portion of the monovalve.

Good luck,

What kind of fitting did you put on?

The reason I ask is that the high side port on my 1991 300TE did not have one installed either; I put on one made by Interdynamics, the kind Wal-Mart sells with the pink "permanent glue" to hold the thing onto the existing R12 service port threads.
I have had no luck getting a good tight connection to this port.
I've used both an Interdyamics and a US General (Harbor Freight Tools) connector to the high side guage set.
I know these aren't high end guage sets but I'm thinking that I should be able to at least get a gas-tight seal in order to read the high side pressure.
I just tried to get my current guage set (the US General /Harbor Freight Tools) to seat on the high side fitting with no luck, and now I have a partially exposed o-ring on the guage set's quick connect
Needless to say I'm not super happy with Interdynamics retro fittings.
I really want to be able to read the high side; I'm tempted to try to remove the Interdynamics fitting and see if I get a seal using the old R12 port to my guage set without the adapter, and next summer switching the system back to R12...

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Bob Roe
Lehigh Valley PA USA
1973 Olds 88, 1972 MB 280SE, 1978 Datsun 280Z, 1971 Ford T-Bird, 1972 Olds 88, 1983 Nissan Sentra, 1985 Sentra, 1973 230.6, 1990 Acura Integra, 1991 Volvo 940GLE wagon, 1983 300SD, 1984 300SD, 1995 Subaru Legacy L wagon, 2002 Mountaineer, 1991 300TE wagon, 2008 Murano, 2007 R320CDI 4Matic 52K, some Hyundai, 2008 BMW 535xi wagon, all gone... currently
2007 Honda Odyssey Touring, 2014 E350 4matic