R134a Conversion

[LOUDSHO92]

Since I am building a new motor I was thinking of possibly changing over the AC to R134 using junkyard parts if I can find them. I all I need the compresor (belt driven part) and the evporator core (part attached at the firewall) and all of the piping? Then just chang out seals if need be?

The other thing I would need to know about is, are the pullies the same for the compresors? I have an old SHOShop UDP set and I would like to know if it will work on a 93+ compresor.

Are the compresors the same on ATX and MTX and the piping just different?

Now for chaging over to R134a I have heard that people have gone from just charging a R12 system with R134a to going and changing every part. I know some have done a variety of ways of changing over.

For those who have just charged with R134a (or any variations) did it work and how long did it work? Any other comments would be appreciated.

Thanks.

 

[Dan H]

I don't think the SS UDP set includes a pulley for the AC, due to the compressor clutch design; at WOT the AC won't be on anyhow. I think the pulleys are the same size for all Gen II SHOs.

I think you can simply charge with R134a and the only downside is a little bit shorter compressor life. Not sure about the seals.

 

[LOUDSHO92]

Oh yeah I forgot about that. I didnt install the UDPs, so I guess I wouldnt know. I know soem systmes can not handle being charged with R134a, I was wanting to know if ours can handle it.

 

[jedhead]

You can go with R406 and don't have change anything.

Bob

 

[SHOtimer]

Well generally you can go about a retrofit in a couple different ways. But, IIRC your AC system doesn't function right now, right? In that case, and especially since you will have the motor out, it will be quite easy to do. You need a new accumulator (must be new), compressor (needs to be R134a), and a new orfice tube (you should get the after market "VOV" type instead of the factory "FOT" type. When all this is out you should get the condenser flushed and checked for leaks, which is a very small price. Also, change all the O-rings, but with the motor out that will take about 10-15 min.

You have a PM.

Doug

 

[jelloslug]

I did not change a thing except for the oil when I did my conversion and it has worked fine for 2 years now with the factory (almost 200k mile) compressor. If the system has sat open for any length of time you should replace the accumulator and you should replace any leaky o-rings. The key to making it work is to vacuum the system to at least 27 in/hg for at least 30-60 minutes

 

[SeanMc]

Get your blender door fixed first . Mine is stuck on hot as well.

 

[rangerj]

The components of an A/C system, with the exception of the "O" rings, the oil, and the refrigerant (e.g. R-134a), are not specific to the refrigerant. A compressor is a compressor. The SHO specific compressor is an 10P15F Nippondenso compressor.

If the compressor you have has R-12 oil in it simply drain the oil out of the compressor. DO NO ATTEMPT TO CLEAN THE COMPRESSOR. You can check the compressor with a torque wrench while it is out of the vehicle. If it takes much more than 84 inch pounds of turning torque to turn the compressor crankshaft it should be replaced.

The A/C condenser should be taken to a radiator or A/C shop to be checked for leaks and cleaned. The evaporator core can be cleaned by pushing cleaning fluid through it through the connection at the firewall with compressed air or a pressurized tank of cleaning fluid. The cleaning kits are available either at your local parts store or via one of several "on-line" distributors.

The oriface line and the accumulator/dryer line should be replaced with new lines. All "O" rings should be replaced with "O" rings made for R-134a. DO NOT USE ANY OTHER CHEMICAL REFRIGERANT. Note: It would be a good idea to get a Ford R-134a conversion kit that has the "O" rings and garter springs. Some kits also provide the R-134a compatable refrigerant oil.

The oil is put in the components, 4 to 5 ounces in the compressor, an ounce in the oriface line, an ounce in the accumulator dryer line and an ounce in the condenser. NO MORE THAN 8 OUNCES OF OIL SHOULD BE IN THE ENTIRE SYSTEM.

Once it is all assembled the system should be vacuumed down to a minimum of 27 inches of vacuum (27 to 30) for a minimum of 45 minutes to an hour. Then let the system set and check for any leak down of the vacuum. If it leaks find out why and fix it. If it does not leak down after about a half an hour, vacuum again for another 45 minutes to an hour. Moisture (water) will boil at room temperature under a vacuum. The vacuum process is intended to remove moisture from the system. You would not want water in the crankcase would you?

When the vacuum process is complete start the engine and put the A/C on full (MAX). Add the refrigerant. The system takes about 30 ounces of refrigerant. The low pressure side should be at about 50 psi and the high side pressure at about 250 psi. The center vent temperature in the cabin should be 40 degrees or less if the outside temperature is 70 to 80 degrees.

 

[Dan H]

Matt,

FWIW my 92 has had R134a in it since I got it. I'm not sure what Shawn or Mike did to it for the conversion, but every part seems to be stock, the compressor, accumulator, and orifice are definitely stock.

 

[LOUDSHO92]

Okay cool thanks. I was just seeing if I should take care of anything while the motor is our. If I can do simple R134a conversion I would rather do that.

I know the blend door needs to get fixed, thats next.

 

[SHO_Diehard]

I found some info on the VOT (variable orifice tube) that SHOtimer was talking about. I would definitely try to find one of those if I was way into the system. The biggest problem I have had with my '89 has been the orifice tube getting partially plugged, which is a different problem, but it illustrates how sensitive the system is to the orifice tube operating properly. When I started working on the AC, I was surprised to find out the orifice tube was the OEM way of controlling the system, I should have known they would save a few bucks and go with something as crude as that.

Concerning getting water out of the system, by the book you need to get to better than 29 inches of vacuum to boil water at 70 deg F. At 28 inches of vacuum, the gas left in the system is about 50% air and 50% water vapor. IMHO, the best way to purge the system is to pull a good vacuum, pressurize with some freon, then pull the vacuum again. This will also help get any traces of air out of the system. This is probably not an "authorized" way of doing it because you are putting some freon to the atmosphere when you do the purges.

One other thing about incompatible components in the system. The refrigerant lines are not compatible with the power steering pump pulley, make sure the lines are secured up next to the firewall. Don't ask how I know that.

 

[SHOtimer]

I bought my "VOV" orfice tube from Kragen. Looking online underneath the AC section, it was under "Hose, Liquid". It listed a 'Ready Air' orfice tube, with optional "VOV" if you add a 'V' after the part number when ordering. The "VOV" tube was double the price, but after looking into it I'm confident it is well worth the difference.

Dave Ladely had some very useful info about the "VOV" in my post a little less than a year ago. Here is all the infor He had to say: IT IS A LOT:

You can find all the info in it's entirety in this thread from posts #'s 19-22

http://www.shoforum.com/showthread.php?t=31523&highlight=Orfice+Tube

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I'd like to pass on some good information. I was never really satisfied with the operation of my AC System since my changeover to R134A. I could only get 55 degree air temp out of the vents and the pressures were very touchy. I used the proper expansion valve for R134A. Flushed & Evacuated the system and installed a new Accumulator. And had the the correct oil charge.

I read on this board and other sites about a Smart VOV (Variable Orafice Valve), working wonders in some systems. So I gave it a try. I was able to get it through NAPA with a one day wait for around $26.00.

Let me tell you!! What a difference. The vent temps seem to be about 10 degrees cooler and my pressures are much better now. It's a pleasure to drive now on these hot days.

For anyone with a similar problem, this is a totally worthwhile investment. It fits perfectly in place of the old Expansion Valve and installs in minutes. Not counting evacuating the system.


Note: I also had the Variable Orifice Tube installed in my 1993 SHO while changing to R134. I know R134 is supposed to be inferior in cooling to R12, but with the variable orifice valve installed, it actually cooled noticabley better than the R12 system, very cool. Of course, the R12 with a VOV would likely cool even better, but R12 is history, realistically.

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The Variable Orifice Tube for A/C provides several serious benefits for about $30.00

5° - 12°F colder air (at hot idle)
Reduced compressor load and extended compressor life
Improved performance when converting from R-12 to R-134a
Improved city fuel economy & emissions
Improved performance in factory R134a systems

How it works


The Smart VOV (variable orifice valve) uses system pressure and refrigerant flow to move a metering piston relative to a fixed opening in the sleeve. The piston movement is resisted by an attached spring.

When idling at high ambient temperatures, the piston shifts to a smaller metering area similar to a TXV. This compensates for the reduced compressor output and increases the cooling performance. The Smart VOV also has a unique re-open feature which reduces compressor pressure for severe idle conditions.

At highway speeds, the Smart VOV operates on a large orifice. The net result is better performance than a TXV without the complexity or reliability concerns.

Unlike a TXV, which has constantly moving parts and small internal clearances, the Smart VOV is stationary during most operating conditions and has large internal clearances. Its low friction floating design insures smooth operation and extremely long life.
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Doug

 

[HighSpeed]

Concerning getting water out of the system, by the book you need to get to better than 29 inches of vacuum to boil water at 70 deg F. At 28 inches of vacuum, the gas left in the system is about 50% air and 50% water vapor. IMHO, the best way to purge the system is to pull a good vacuum, pressurize with some freon, then pull the vacuum again. This will also help get any traces of air out of the system. This is probably not an "authorized" way of doing it because you are putting some freon to the atmosphere when you do the purges.

The proper way to do it is, pull vacuum, let it sit there to see if the vacuum holds. If the vacuum holds after a min of 45 mins, you need to apply dry nitrogen into the system, look at the manual or data plate on how much dry nitrogen you need to feed, its measured in psi. Applying dry nitrogen will help remove any moisture in the line. The dry nitrogen is just vented off to atmosphere, since its harmless. You do not recover the dry nitrogen. After this, u can then charge the refrigerant accordingly.

Pull vacuum better than -29" Hg? A perfect vacuum is -30" Hg. Vacuum is measured in the negative inches of mercury. pressure(in psi) and vacuum(in X" mercury) are opposites of each other. FYI

If you use a micron gauge, and if you can achieve 200-500 microns, this will be more than sufficient even though your compound gauge is reading -28: Hg or so.

 

[HighSpeed]

I did not change a thing except for the oil when I did my conversion and it has worked fine for 2 years now with the factory (almost 200k mile) compressor. If the system has sat open for any length of time you should replace the accumulator and you should replace any leaky o-rings. The key to making it work is to vacuum the system to at least 27 in/hg for at least 30-60 minutes

The key word I would suggest is to hold vacuum, this means turning off the vacuum pump and let the system sit there to see if it holds vacuum.

Don't take this the wrong way, you didn't do it properly, however, its your sho. R12 and R134a is not compatible, the different refrigerant will sludge up you compressor. R12 decomposes to form hydroflouric, hydrochloric and phosgene gases. Acids in your compressor is not a good thing.

 

[SHO_Diehard]

The proper way to do it is, pull vacuum, let it sit there to see if the vacuum holds. If the vacuum holds after a min of 45 mins, you need to apply dry nitrogen into the system, look at the manual or data plate on how much dry nitrogen you need to feed, its measured in psi. Applying dry nitrogen will help remove any moisture in the line. The dry nitrogen is just vented off to atmosphere, since its harmless. You do not recover the dry nitrogen. After this, u can then charge the refrigerant accordingly.

The freon and dry nitrogen are doing the same thing, diluting the remaining air and water vapor in the system so you can vacuum it out. Most of us don't have nitrogen cylinders sitting around in the garage, so the freon is more practical.

Pull vacuum better than -29" Hg? A perfect vacuum is -30" Hg. Vacuum is measured in the negative inches of mercury. pressure(in psi) and vacuum(in X" mercury) are opposites of each other. FYI

Point is the pressure to boil water at ambient temp is quite low, the dilution effect of the freon (or nitrogen) makes a big difference, especially if the vacuum pulled isn't that great.

As for the relative and absolute pressure stuff, I'm very familiar with that, although some of the other members probably are not.

Anyway,

 

[etc1006]

Most conversion kits use POE oil. It is compatable (miscable) with the mineral (R12) and synthetic (R134) oils. Just a R134 "recharge" can will probably have PAG oil which synthetic and not compatable (miscable) with the mineal (r12) oil. Check your labels before buying!

 

[Mr Anonymous]

Yeah, a year later that's probably a little late...