[W126 Coupe] 1985 euro version 500 SEC

[Jonathan Hodgman]

Well, to start...I wouldn't convert it if the car has R12 keep it that way!


You did forget to flush the whole system..  Mineral (R12 oil) and PAG (R134a
oil) are not compatible..and the two together form a nasty goo that does a
Fabulous job of clogging expansion valves (i've changed 3 to date from
cheap/half ass'd 134a conversions).
When you do a flush the only way to be reasonably assured all the old oil
out is to remove the expansion valve...flush does not readily move through
there so in order to clean the evap it needs to be out.  You already
replaced the compressor which is good...you an also remove an old compressor
and drain/flush it outside the system.

A couple of things to keep in mind, I'm not sure where you live but if you
see temps over 90 w/ any regularity you won't be thrilled by the performance
of a retrofitted 134 system.  Also, most AC techs refer to 134 as the 60mph
refrigerant, ie, it doesn't really work well until you are up to speed.
Head pressures are also going to be High..these systems were designed w/
around 200-250lb pressures in mind w/ R12..  The vast majority of 134a
retrofits I see run in the 3-400lb range...something all your AC commentary
does Not appreciate..esp. any weak spots in your evaporator.

All of that aside, in order to get refrigerant into your car you'll want to
jumper the compressor to come on, either via the switches on the dryer or by
bring 12v's directly to the compressor.

Lastly, Anytime the AC system is opened you need to replace the
dryer...ESPECIALLY if you are doing a conversion..which again I recommend
you don't.

If you ever plan to sell this car having it still equipped w/ R12 will be a
selling point, where as I see a 134a conversion as a major detractor.

Jonathan.

btw, nice diff bruce!


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