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what steps to convert from r-12

bjolly on Wed May 22, 2013 10:39 AM User is offlineView users profile

Year: 1993
Make: toyota
Model: camry
Engine Size: 2.2L
Refrigerant Type: r-12
Ambient Temp: 85
Country of Origin: United States

My daughter's 93 Camry's AC has not worked for a couple of years.
Would like to get it working for a graduation present.
Right now the system is R-12.
What steps and procedures should be taken to update and re-charge this system ?

TRB on Wed May 22, 2013 11:47 AM User is offlineView users profile

Minimum requirements for converting a system to R134a.

If system has any refrigerant R12 left in the system it must be reclaimed by an approved recovery machine.

Accumulator/drier must be replaced with an R134a compatible replacement. Conversion fittings and label must be added to the system. Label should have the amount of R134a used and quantity and oil type listed. If vehicle is not equipped with a high pressure cut off switch it must be added. That is the required minimum! While complying with the EPA laws may not provide the best performance.

Flushing the system to remove the mineral oil and debris should also be done. R134a and mineral oil do not work well together so leaving it in the system with R134a is not recommended! O-rings should be replaced with either NBR or HNBR replacements. Adjustment of the pressure cycling switch may also be needed to achieve the best performance. In some cases an upgrade of the condenser may be required to achieve the original performance. In many cases the parallel flow condenser will not be available as a direct replacement. Using a universal parallel flow is an option. A new custom hose set would be needed for the different style fittings used on the various parallel flow condensers.

There are many different suggestions when charging a R12 system with R134a. System must be evacuated before starting the charging procedure. I suggest you start with about 70 percent of the original R12 charge and add an ounce at a time until vent and pressure readings reach the best available results. Remember it is easy to over charge a system with R134a so patience is important.

Option 2: Repair the system and stay with R12. It will cool better and as long as you don;t have a leak. Overall it won;t cost that much more to get the system up and running.


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bjolly on Sun May 26, 2013 7:00 PM User is offlineView users profile

Thank you. I think I'll try the R-12 route.

mk378 on Sun May 26, 2013 7:23 PM User is offline

Find the leak first. If all the R-12 is gone there must be a leak. If most or all of the R-12 is still there then it could be some other problem i.e. electrical.

After opening a R-12 system to work on it, don't recharge with R-12 without a thorough leak test under pressure first. You can use a small amount of 134a for leak testing. This is not a conversion; do not change the oil, it is not necessary since you won't run the compressor. Unplug the compressor clutch to make sure it won't run. Charge to about 50 psi and go over the whole system with an electronic leak detector. Then wait a couple of days and check the pressure again to make sure the 134a is still there. Evacuate the R-134a (EPA says it is legal to just vent it, since it was used as a leak testing agent not a refrigerant), and charge with R-12.

Olds442 on Tue May 28, 2013 4:03 PM User is offline

Olds442 on Tue May 28, 2013 4:06 PM User is offline

Yes, I'd say keep it R-12. Your system was designed for R-12 and it cools better than R-134. Plus, you don't have to replace hundreds of dollars worth of parts and
change the oil. Seems like a no-brainer to me.

WyrTwister on Wed May 29, 2013 6:21 AM User is offlineView users profile

I was under the impression , R12 , if it can still be found , is prohibitively expensive ?

God bless

94RX-7 on Wed May 29, 2013 7:07 AM User is offline

I bought some a few months back on Craigslist....I paid $12.50 per 12 ounce can. Cheaper than some places are selling R-134a for.

mk378 on Wed May 29, 2013 4:44 PM User is offline

There is lots of New Old Stock R-12 around. Buying from a guy on craigslist you have to watch out for bogus substitute refrigerant -- HC blends that have "12" in the name.

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