Proper R134A Conversion for 124? - PeachParts Mercedes-Benz Forum

JamesDean · #13 05-22-2013, 08:31 AM

Does your 300E have the 10P15C or 10P17C compressor?

I found this comment on the two:

Quote:

Originally Posted by stevebfl

I have converted hundreds of cars to 134, maybe a thousand. Probably a hundred 300Es. BUT I haven't done a pre 1990 300E in almost 2 years. I do not do them if they have the 10p15c or 10pa15c compressors. This is writen on the back head of the compressor. These small compressors do not handle the extra load well; they didn't do great in R12 and they ABSOLUTELY will not do better in R134a. There is an absolute 5% decrease in thermal efficiency with R134a.

If you wish to convert (DON"T do it) fix your system first in R12 till it is cold enough to suit you and then make your decision.

Quote:

Originally Posted by Air&Road

I was looking at a 92 300D one time that was factory 134a. For all I know it was the last 92 model ever made.

The later models use a 10P17 compressor. By changing the bracketry on an earlier engine, you can use this compressor. The mount holes are farther apart fore and aft than those of a 10P15 or 10PA15.

I am almost thinking about researching swapping the 15 out for the 17. My 420SEL has the 17 with R12, which does very very well.

However, keeping the 15, I think eventually that is the path I will take.

Replace every seal.
Remove the evap, clean it out.
Remove the condenser, clean it out.
Replace the schrader valves. Actually it has quick-connects on it now..
Pressure test. Is there any reason you chose 180 psi as opposed to something higher?
Verify
Verify
Charge with R12.

Today on the way up I stuck a thermometer in the center vent. 72F outside 74% humidity, at highway speed, I got about 48 at the vent. So a 24F temperature differential. Not horrible, but probably not as good as R12 or the ES-12A that I have in the 190E. I will get another reading on the way home today where it will undoubtedly be warmer. Tomorrow I'll be in the 190E so I can get that data as well.

Based on the charts provided in the 88-608 pdf:

At my conditions I should expect to see:
40% - 90% (Humidity)
260 PSI - 320 PSI (High)
14 PSI - 30 PSI (Low)
40 F - 46 F (Vent)

I believe there is a 10-15% efficiency loss with 134A...so my numbers were on par with what would be expected?