Been doing a little research and it looks like I need to do this conversion. My A/C system (1992 300E) seems to
work marginal, I get some cooling but not enough. I plan to purchase a conversion kit from Advance Auto Parts
and order/replace the Receiver/Drier. I'm not a professional mechanic but am capeable of basic maintenance such
as tune-ups and oil changes.

Would appreciate any words of wisdom regarding this process. I am also concerned about CFC's but don't
have the tool to evacuate my R12 prior to conversion...so...there goes the ozone layer. Local shops want
$800 to do this conversion! Parts extra! I can purchase the conversion kit for $60 and a new drier for $50.

Please offer any experienced info you have.

Much Thanks!
Bruce

 

Well whatever you do, don't mix R12 with R134. I don't remember why but it is supposed to be bad.

I suggest having the local shop only evacuate the R12 out and doing the conversion yourself.

my .02,
Andrew

 

I had a 90 MBZ 300E and had the conversion done also. It is really not much to it. I had a guy at a Repair Shop do it and he charged me all of about $60.00
Your biggest problem is going to be finding someone that will do it and not rip you off. All they do is evacuate your R-12 and then replace the fittings to accept the hardware for the 134A and then fill you back you and charge the system. I had mine done in CT. If you are in the Bay Area of CA, I may have someone for you there. Good Luck

 

Most of that $800 they want is probably for a new compressor. I've heard that the new R134 shortens the life of the old R12 compressors. I don't believe there is any truth to this, some have told me that their compressor went out about a year after the conversion, but most say it's been X number of years and it is still working fine.

I recommend having a shop evacuate the R12 out,
Buying the conversion kit and fitting it yourself (only takes a few turnes with a wrench)
Replace the drier (not extremely important but highly recommended, your supposed to change it everytime the AC is worked on.),
And recharging it (special hose attached to a can of R134 and low pressure side while compressor and engine are operating)
It's really no big deal...

That's
Whatever the shop wants for evacuating the system
$60 for the conversion kit ($25 for the universal kind)
$50 for the drier (or not...)
and about $10 per 4oz can of R134.
oh, and maybe a maximum of one hour of labor...

That's a lot cheaper than $800

Andrew

 

something to know easy rider r134a will not cool as good as r12 my suggestion is try to keep it r12 for a while longer

 

What about Freeze 12? How does it compare to 134a and 12?

 

To perform a successful R12 to R134 conversion is really quite simple and you should have no problem performing this operation yourself. First evacuate your system by letting all the pressure out. As long as you had pressure in your system before, moisture contamination should be minimal and vaccuuming down the system to remove moisture really shouldn't be necessary. Next install your new reciever drier and pressure switches if necessary. This will be on the high side of the system and its purpose is to provide a constant liquid supply of refrigerant to the evaporator. This device will have a large ammount of R-12 mineral oil built up in it, which is not compatible with R134. PAG or Esther oil must be used with R134 because mineral oil will not mix with the 134 in order to get to the compressor to lubricate it. If you do not want to replace the reciever dryer you can also remove it and turn it upside down for 30 min to drain the oil out of it.

Next, you can do this the right way and remove your compressor and turn it upside down to drain out the oil, or you can leave it be and you will probably be ok. Leaving it be will actually be your best bet though if you are buying a conversion kit, as they often come with an oil charge that they claim to be compatible with mineral oil. After everything is back together and you screw your new fittings on top of your old r12 service ports, you are ready to charge. I start by injecting the oil charge in the low side with the can upside down. Then figure out your system capacity and determine how many cans of refrigerant you will need. If using small cans, let one can into the high side with the can upside down and then let the rest into the low side with the can in the upright position. The last can will go into the system very slowly, so turn on the car and ac so that the compressor will pull the refrigerant out of the can. It will feel like there is still stuff in the can but this might be leak sealer mixed in with the refrigerant. You will know enough refrigerant is in the system when the air coming out of the vents feels cold enough.

Just make sure not to turn the car on and run the compressor with the can connected to the high side. For your reference, the section between the compressor and passenger compartment (evaporator) is the low side. The high side is everything in the circuit from the compressor to the condensor (in front of radiator) to the reciever dryer, to the evaporator. The high side will be warm to the touch and low side will be cold to the touch.

Sorry for the long post. Good luck.