r-134 converted 190 16 valve.

I have a 1986 190e 2.3-16 valve that has been converted to r-134 refrigerant. I followed the 80% rule in refilling the capacity aand found that this does not work. All cars are different in how they react to the refilling. I had the shop refill the car to 1.8 lbs, 80% of the original r-12 2.2 lbs specs. The low pressure switch blew and the car never really got cold enough when the temps hit 90 plus. Upon replacing the low pressure switch, I asked the shop to refill the 134 refrigerant to 1 lb( 16 oz). The car can keep up with the weather now. I think that the car was filled to much using the 80%rule. I suggest to all r134 conversions to try filling to 50% of capacity and see how the a/c handles in the heat. Thanks, Joe

Try going to http://www.aircondition.com. This website gives lots of useful info as well.

Brother of The Benz, joe 1
My W124030, converted to R-134A and off charging by 20% cools fine and doesn't blow any switches.
My capacity is 2.2 lbs of R-12 or 1.76 lbs of R-134A.
In filling from empty, this requires 2.34 cans at 12 oz/can total of 28 oz.
Charging only using 2 cans plus the 4 oz included in the oil charge if used totals at 28 oz.
If your system had any of the super additives put in, then you may be overcharge by the amount of R-134A included in each option.
joe1, you did right by reducing the amount of gas, but I think you went to the extreme.
Try adding one more 12 oz. can.
You Do have the low side pressure gauge don't you?
If NO, help yourself and get one.
Walmart and K-Mart have them.
As to handling R-134A in the heat in Houston, 98+ degree days and no problems.
If you were overcharged, then the condenser was super hot and that heat is passed on to the rediator.
Your A/C isn't keeping up with the weather it's just blowing cooled air in your face and on your hands.
The rections of all cars A/C in excellent condition and properly filled are the same.
Same high and low pressures; for these are what the system is designed for.
There is no reason to reccomend reducing the capacity to 1 lb.
For by doing this you have a dangeriously low liquid level in the evaporator and a reduced amount of oil in circulation that is required by the compresser.
To gaurantee oil return through the low pressure hose, the oil must boil over the evaporator top tube, and at your level it can't.
My Benz when in traffic indicates between 80 & 90 on the dash indicater. It may indicate 100 on one of those oven type days or;
While stopped in traffic,I slip the transmission to Nuetral and increase the engine speed to 1500 rpm. This increased air flow helps emensly.
Happy Trails Beep Beep from The Spiderman in Houston!!!

I forgot to mention that my car is a total 134 conversion. Compressor, o rings, high and low pressure switches, and dryer. I know yours is a retrofit. Sorry I failed to mention this before. Joe

While I had my engine out and doing things to it, I put on new compressor, drier, cleaned out condensor and lines, put in some new o-rings and recharged with 134a and ester oil. My little 380sl never cooled better! I did not have to change expansion valve. Like I said, it works great. If anyone has problems with their system, I would suspect a weak link somewhere else in the over all scheme.