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Black Death


Explorer Addict
April 25, 2005
Reaction score
City, State
Friensdwood, Texas
Year, Model & Trim Level
91 Mazda Navajo
I've started my R12 to R134a change. I got a rebuilt compressor, accumulator and expansion valve for $265. I've attached a picture of the expansion valve. Now I'm changing the hoses ($150) and condensor ($158). Tomorrow I'll backflush the evaporator, put all the parts in, pull a vacuum and recharge.
The compressor came with PAG 100. Can someone confirm the following loads please?
2 oz = 1/4 cup
2 oz in condensor
3-4 oz in compressor (turning by hand)
3-4 oz in accumulator

I'm guessing 28 oz of R134a



  • Expansion valve.JPG
    Expansion valve.JPG
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You should be ok with those amounts of oil but if the compressor comes precharged with oil... you should drain it into a clean container and if it is short of the amount needed add some and put it back in. Remember that for a converted system you only need about 70-75% of R-134 as the system called for for R-12 (Some even suggest starting at 60% and then measuring vent temps. ) You are doing it correctly.... I am sure you will be happy with the result. That hose from the evaporator back to the compressor, with the little "muffler" on it is a great trap for debris. In a bad case of black death I replace it, even though the odds are the orifice valve and evap trapped most everything. Better safe than sorry. Thanks for the pics... good illustration.

Thanks for the support. According to Haynes the 91 Navajo had a 32 oz R12 charge and the 94 Explorer has a 26 oz charge of R134a. That's roughly 80%.
I'll put in 24 oz then feel the evapoator in and out and try to tune. The compressor came with a tag that said empty.

Where did you find the supplies for this project? I'm pretty sure that my '92 has the R-12 system, but I'm not positive?? Its definitely lost the charge, whatever coolant is used, so i figure I want to do the conversion if it does run R-12. A detailed writeup would be awesome. Good luck too.

whats the benefits of doing this?

92 was R-12. Review the thread here about converting your AC to use 134. It also has links to suppliers... but a good bet is a local auto ac parts house. If your town does not have one I can refer you to mine here in Sacramento CA.

Benefits of a conversion from R-12 to 134 is that R-12 is becoming scarce and is VERY expensive. Downside is that a system designed for R-12 lacks adequate condensor capacity needed for 134 and will not perform as well as the R-12 system...(close in some cases).

As Glacier991 says, There are some good threads regarding conversion. I know I have a bad compressor, there's a spray line of oil underneath my hood. So technically I guess I'm upgrading rather than converting.
I got the kit on ebay, it contains a remanufactured compressor, orifice tube, accumulator and oil. There are a number of vendors with varying prices.
As you can see from the picture above, the black crud in the orifice tube means that I have to change the condensor (hopelessly crudded). I changed the hoses because mine have deteriorated and, as Glacier991 points out, the muffler may have trapped particles. I flushed the evaporator with isopropyl alcohol, there are commercial products that are better.
The reman compressor I got had a ding on the suction o-ring outer channel and won't hold pressure, the company's sending out another one on Monday so I'll continue then.

In the meantime, does anyone know the correct toque value for the bolt securing the refrigerant lines on the back of the compressor?

15 ft lbs, plus or minus 2.