[W126 Coupe]A/C Conversion 1985 euro version 500 SEC

[jeffrey maniff]

Jonathan,
Thank you for the response.  I will show your email to the tech that helped 
me change out the compressor and we can discuss that with him.  Do you off 
any advice on where to get a reaonably priced dryer?  Also, where or how can 
I maintain the original ac system once the compressor has been replaced.  I 
have not done any conversions to the system at all and the compressor comes 
right on and is working it is just that it will not take in the R134.  
Possibly a dryer problem or the problem you mention regarding the gunked up 
pipes.  Either way, I appreciate your insight and thank you.
Jeff Maniff (massachusetts)


>From: "Jonathan Hodgman" <jhodgman at gmail.com>
>Reply-To: Mercedes Coupes Mailing Lists <mbcoupes at mbcoupes.com>
>To: "Mercedes Coupes Mailing Lists" <mbcoupes at mbcoupes.com>
>Subject: Re: [W126 Coupe] 1985 euro version 500 SEC
>Date: Sat, 2 Sep 2006 13:37:16 -0400
>
>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!
>
>
>--
>Blue Ridge Mercedes
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