A/C retrofit question.

[josh89xj]

I have a 89 xj 4.0L Im retroing the system and since i pained my engine compartment i cannot find the r-12 specs anymore.Does anyone know the r-12 capacity?I need to know how many pounds of r-12 to fill so I can convert the r-134a.

 

[Masterblaster]

36 ozs. is what the book says. I used less when I did mine. Make sure you have the system purged of all the R-12. I bought a conversion kit at Advance for about 25 bucks and it had everything you need to do this job. It is imperative that you have the old R-12 purged because the oil in the 134A is not compatable with the oil used with the R-12.

 

[josh89xj]

My system had a bad leak and leaked all the r-12 out.I replcaed the leaking part and filled,thats going to be ok right?

 

[Rick Anderson]

My system had a bad leak and leaked all the r-12 out.I replcaed the leaking part and filled,thats going to be ok right?

NO its not going to be OK.

You filled it with R-12 or R-134a?

If you filled it with R-12, it sounds like you did NOT add any oil. There are specs for how much oil you should add for replaced part because the oil gets distrubutited in the system and thus some trapped oil is removed with the old part. As well, the oil mixes with the refrigerant and it leaks out with the refrigerant, so you should always add a little more than what is called for when replacing the part to get the oil level back up. There is no way to check the oil level in an AC system, you can only guess with some guidance from the book, so you should always guess heavy and add a little more than you need. Your most likely low on oil for the AC system and it will wear out sooner, if not sieze up.

If you filled with R-134a, your in real trouble, R-12 systems use mineral oil, which is NOT COMPATIBLE with R-134a, the oil won't mix with the refrigerant and it won't get circulated thru the system, it will just lay at the lowest point and NOT lubricate the compressor. Your system is going to sieze up in a short time.

If your going to retrofit R-12 system with R-134a you need to do your research. At the very least, you have to purge all the old R-12 and oil out of the system before you fill it with the PROPER AMOUNT OF R-134a which is less weight than the original R-12 capacity and the PROPER OIL THAT IS COMPATIBLE WITH R-134a. There are some retro-fit kits out there that have you fill the system with R-134a and POE oil, leaving the old mineral oil, don't use them. It may work for a while, but its likely to fail in short order. The R-134a OIL is not Compatible with the R-12 Oil, so if you mix them, your oil is going to go bad. PAO oil is definitely not compatible with mineral oil, POE is tolerant of a little mineral oil, but if you mix POE 50/50 with mineral oil, the POE is going to bad after a while, as well, a 50/50 mix of compatible/non-compatible oil with R-134a is NOT going to mix and circulate as well with the refrigerant and lubricate the system properly. As well, that useless mineral oil is taking space that could be used for refrigerant that would help cool the system that has already lost cooling capacity from the conversion to R-134a. You get the point, if your going to convert to R-134a, the only proper way to do it is too completly purge the system of the old R-12 and its oil. AND THATS ONLY ONE OF A DOZEN THINGS TO CONSIDER AND DO WHEN DOING A PROPER CONVERSION.

Also, R-134a is a smaller, lighter molecue with different pressure properties, you should only add about 75%-80% of the capacity for a R-12 system. Since the molecues are smaller and lighter, you get more molecues per Oz than you do with R-134a, so if you put the same weight R-134a in a R-12 system, you've overcharged it with to much refrigerant. Look up Boil's Law and refresh what you learned in High School, AC works off the Pressure/Temp relationship in a constant volume, using phase change in the refrigerant from liquid/vapor to gas. You'll see the number of molecues is what fill the system, not the weight/volume of the refrigerant.

(Check the 75%-80% figure, Its been a while) If you fill to the same R-12 Capacity with R-134a its overcharged and the pressures will sky rocket and you'll likely blow a seal, burst a part or burn up the compressor working against the super high pressures.

 

[Rick Anderson]

My system had a bad leak and leaked all the r-12 out.I replcaed the leaking part and filled,thats going to be ok right?

Did you replace the Filter/Drier also? Anytime you open an AC system you should replace the Filter/Drier, the system has to be hermetically sealed, the Filter/Drier has a bag of dessicant in it to catch any last remaining moisture in the system. Wait until your ready to service the system before replacing the filter drier, the desicant bag will suck moisture out of the air and fill up if you leave it exposed to air.

So just before you service the system, unseal the new Filter/Drier and replace it.

 

[XgeekstarX]

i charged mine the other day with about 2lbs of r-12 for freeeeeeeee

 

[josh89xj]

How to I get everything out of the system?meaning how to I get the old r-12 and oil out so i can put 134a in without siezing it up?

 

[Pelican]

Find a local shop to evacuate and recover the R-12. They should do this for no charge in exchange for the residual R-12 which is far more valuable than the few minutes of labor thay have to perform.

I've had two done for no charge where the shop offered to do so without my asking and also offered to evacuate again if I had to open the system to install the R-134 fittings (I didn't). Others have reported shops charging for this service so I think I would call around in advance and ask if they would be willing to swap the evacuation for the R-12.

 

[Rick Anderson]

I could only find a shop a to evacuate my R-12 for a $20 fee.

I'm sure they would charge a quite a bit more to flush all the oil out of the system as well.

When I retro-fitted my mini-van (bad canidate and it didn't work too well), I removed all the lines and components and ran a flushing fluid thru it, it was a gallon of flushig fluid I found at my local auto store that was for flushing old R-12 for R-134a retrofit. I used a wet/dry vac to suck the flush thru the components. You could use compressed air as well.

You'll of course, will definitely need a new filter/drier if you do this.

The Compressor you'll have to open up and let drain for a long time, I don't know how to completely flush out a compressor without taking it apart and suppossededly most compressor sould only be taken apart by the factory, they won't go back together right.

For retro-fit, you should use POE oil, its tolerant of any trace amount of mineral oil that will be left over. POA is better, but its not tolerant of much mineral oil.