RE: [DMCForum] Here it comes again... the R134 conversion

[Travis Goodwin <tgoodwin@xxxxxxxxxxxx>]

I can do just about anything on the car but I have never touched an AC
system. How would you rate this conversion as far as difficulty?

> -----Original Message-----
> From: Dave Stragand [mailto:dave.stragand@xxxxxxxxxxxxxxx]
> Sent: Monday, March 15, 2004 1:18 PM
> To: DMCForum@xxxxxxxxxxxxxxx
> Subject: Re: [DMCForum] Here it comes again... the R134 conversion
> 
> >From my FAQ:
> 
> This is a fairly complete checklist for the conversion based on
> Sanden/Sankyo's own instructions, material gathered from the web, and the
> wisdom of those DMC owners who have already completed this procedure.
> 1) If the R-12 vehicle air conditioning system is operational, run it at
> idle with the A/C blower on high speed for five (5) minutes to optimize
> the amount of oil in the compressor.
> 
> 2) Recover all R-12 refrigerant from the vehicle's A/C system.  Evacuate
> the A/C system for at least thirty (30) minutes to a vacuum of 29 in. Hg,
> using R-12 equipment, to remove as much R-12 as possible from the residual
> mineral oil.  Don't just dump the old R12 into the air.  If you really
> don't want it, at least let a service station vacuum it out.  They will
> generally take it very happily, as it is quite expensive, and you won't be
> polluting.
> 
> 3) Remove the compressor from the vehicle, noting the placement of all
> shims and washers, and the routing of hoses and wires.
> 
> 4) Remove the compressor oil plug and then drain as much mineral oil as
> possible from the compressor body.
> 
> 5) Drain mineral oil from the cylinder head suction and discharge ports
> while turning the shaft with a socket wrench on the clutch armature
> retaining nut.
> 
> 6) Remove the existing R-12 receiver-drier or accumulator-drier from the
> vehicle and discard.  Allow as much oil as possible to drain from the A/C
> hoses. Blowing them out with an air gun on moderate pressure is okay.
> Back-flushing the lines is recommended. Plain old mineral spirits swished
> around in the compressor and backflushed through the lines will remove
> contaminants and old mineral oil. Make DARN, DARN sure that you get ALL of
> it out of the system, and I do mean ALL of it.  Mineral spirits can be
> explosive, but a great many a/c shops still use this technique to great
> effect. I would recommend drying everything out with clean dry air from a
> compressor for quite a while (hey, air is free, right?) Commercial a/c
> flushing chemicals are also available which will do the same while being
> safer, but they can be pricey.
> 
> 6) Replace any O-rings on the receiver-drier or accumulator-drier joints;
> check and replace other O-rings that have been disturbed. You really
> should replace them with the new green ones -- they work very well for
> both R12 and R134a.  If you are converting to R134, new reports suggest
> that you do -not- need to change all of the O-rings to different materials
> as thought earlier. However, I would recommend changing anywhere you have
> disconnected a joint, just to help seal better. They're cheap anyway, and
> cheaper than having to do it again because of a leaky seal.
> 
> 7) Replace the accumulator-drier with a new R134a compatible unit which
> contains XH7 or XH9 desiccant. Make sure that you get one with "XH7" or
> "XH9" dessicant, not "XH5" -- there should be a sticker on it stating as
> such.  XH7/9 works just fine with R12 and is necessary with R134's Ester
> or PAG oils.  As a cross-reference, a 1986 Corvette accumulator-drier is
> perfect. Factory Air brand part number 33191 dryer is ideal, and runs
> about $55 at AutoZone.
> 
> 8) While you have the accumulator-drier removed, now is a good time to
> replace the orifice tube.  Always replace it 'just because'.  The type
> used on the DMC is just a standard "white" GM orifice tube used for many
> years on many GM models, and the cost is less than $2. (Any parts counter
> person should know what you mean when you ask for one). There are some
> newer variable orifice tubes claiming to work better with R134a, but I
> have not read very much about them, and I'm a little wary of their claims.
> 
> 9) Perform any necessary repairs to the compressor or A/C system.
> 
> 10) Using the original refrigerant oil quantity specification, add [INSERT
> QUANTITY HERE] ounces of Ester oil to the compressor. Ester oil is
> preferable to PAG in a retrofit, as it will mix fairly well with any
> remaining mineral oil.  It was originally thought this was not the case,
> but consensus nowadays is that they mix satisfactorily.  Ester is also
> less corrosive than PAG.  As an additional benefit, R-12 will also work
> with Ester should you ever wish to convert back.  If you follow these
> guidlines, all you would need to do to revert to R-12 is completely vacuum
> all R134 out of the system and then simply reinstall R-12.
> 
> 11) Replace the compressor oil plug O-ring with an new O-ring.
> 
> 12) Reinstall the compressor oil plug. The plug seat and O-ring must be
> clean and free of damage. Torque the plug to 11-18 ft lb (15-25 N m, 150-
> 250 kgf cm).
> 
> 13) Change any seals at the compressor ports to new seals.
> 
> 14) Reinstall the compressor to the A/C system, paying close attention to
> the placement of shims and washers from step #3.
> 
> 15) Disable the R-12 service fittings to prevent any refrigerant other
> than R134a from being used. You do this by permanently installing R134a
> quick-connect service fittings to the A/C system.
> 
> 16) Vacuum the system for AT LEAST forty-five (45) minutes to a vacuum of
> 29 in. Hg once the lines are cleaned, the new drier installed, the correct
> amount of Ester has been poured in the compressor body, and the whole
> system is ready to go. Harbor Freight makes a cheapy high-vac pump for
> $15. You can hook this up to a spare R134 can adapter hose ($5) to make
> the correct fitting for attaching to the car. And yes, you MUST evacuate
> the lines. This is the most common mistake people have in retrofitting. If
> you don't get that vacuum down in the system, there is no way the air is
> going to blow very cold.
> 
> 17) Charge the A/C system with R134a. Generally, about 5% (by weight) less
> than the R-12 charge amount is required. That means just a little over 2
> pounds for a DMC.
> 
> 18) Check the A/C system operating parameters. The system should function
> correctly within acceptable limits of temperatures and pressures -- this
> will ensure that the correct amount of R134a has been charged.  I
> purchased at a small R134 gauge at Pep Boys for less than $5.  It looks
> much like a tire pressure gauge.  It tells you the system pressure in
> terms of low/good/high/danger. Likewise, they have a small & cheap "meat"
> thermometer that will tell you vent temps inside the car.
> 
> 19) Replace all R-12 compressor labels with retrofit labels per SAE J1660
> in order to provide information on the R134a retrofit which has been
> performed.  In other words, you really should put a sticker on there that
> says it's R134a.  The recommended places are on the compressor and the
> accumulator.
> 
> Additional notes:
> 
> - In extreme circumstances when expected cooling performance cannot be
> achieved and high discharge pressures are experienced, it may be necessary
> to add more condensing capacity to the A/C system.  I believe PJ Grady
> sells a larger capacity condenser for our cars.
> 
> - Sanden has the service manual up for our compressors online at
> http://www.sanden.com/support/servicemanual/index.html
> 
> -Dave
> 
>   ----- Original Message -----
>   From: Travis Goodwin
>   To: 'DMCForum@xxxxxxxxxxxxxxx'
>   Sent: Monday, March 15, 2004 12:46 PM
>   Subject: [DMCForum] Here it comes again... the R134 conversion
> 
> 
>   I desperately need to do this before Pigeon Forge. Last summer I was
> lucky
>   that I didn't have to drive it much since the engine was dismantled.
> This
>   year is a different story.
> 
>   Bill, I know you're the man when it comes to this. Any advice on where
> to
>   start?
> 
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