The AirCon originally came with R12 refrigerant. It can be converted to R134a refrigerant and maintain good performance.
WARNING: The AirCon system is under pressure. Always take proper precautions. Wear eye protection and rubber gloves. Avoid getting lubrication oil and refrigerant on skin. The new PAG oils can harm you and refrigerant can freeze skin quickly.
The AirCon compressor is the same as used on the 1989 Isuzu I-Mark L4 1.6L F.I. It is a Diesel Kiki DKS-13G with a 5 grooved pulley. Compressor International Inc. has a replacement compressor listed at http://www.compressor-intl.com/HTML/is89.htm. Compressor International Inc. will do a rebuild on your existing compressor for $230.79 plus shipping as of 6/28/2012. They recommend you send in your existing compressor for rebuild to eliminate any chance that you get the wrong compressor.
The receiver/drier has an upward tilted male fitting for the female trinary switch. Many replacement receiver dryers have this fitting at a 90° angle which will be difficult or impossible to fit. Rockauto.com has the correct receiver/drier with the angled male sensor screw for the stock female factory trinary switch. It's the Four Seasons part 33276 used on the 1989 Isuzu Impulse and it's only $12.75 plus shipping as of 6/28/2012. This receiver dryer is a little larger in diameter than the original so it may be necessary to leave the foam off when fitting this part.
At least half of the mineral oil in the system needs to be replaced with the proper PAG 46 refrigerant oil. Using an oil that contains a UV dye will make it easier to do leak detection.
Conversion to R134a
Things to know about conversion to R 134a:
- You don't need to flush the entire system if you don't have a catastrophic compressor failure.
- Even then, you can use an inline filter on the suction line instead of flushing (some manufacturers recommend filters instead of flushing) as long as nothing is clogged with debris. Putting in a filter as insurance against random debris is good practice even if you didn't have a catastrophic failure. Autozone seems to be the only USA autoparts chain that carries the thimble inline filters that let you avoid cutting a line to put in a filter. These are AirSept/A/C Inline Filter Kit part number 67576.
- If things are clogged you have to replace the expansion valve which requires removing the dash as this cannot be flushed.
- Always replace the receiver/drier.
- You need to get at least one half of the old mineral oil out. You can do this by draining the compressor, receiver dryer, and blowing out the condenser with compressed air. Collect this so you know how much you've gotten. The system has about 5.3 oz. of oil.
- The existing seals and hoses can be used if you don't flush them. Mineral oil acts as a sealant and flushing removes it.
- You have to replace any seals in joints you open with R134a resistant seals.
- R134A uses approximately 80% of the R12 charge or 24 ounces instead of 28 ± 2 ounces.
Steps to convert.
1. Get the old R12 out of the system - there may be restrictions on how you do this though as an individual they may not apply to you.
2. Replace the receiver/drier. Add 0.5 oz. PAG46 oil to the new receiver/drier.
3. Punch holes in the bottom of the old receiver dryer and drain the oil into a measuring cup noting the amount.
4. Drain the oil out of the compressor, again noting the amount. (Note: I had the compressor rebuilt so I'm not sure if you can do this without removing the compressor. There is a drain plug that can be removed from the compressor.)
5. If you have drained less than 2.5 oz. of oil, blow out the oil out of the condenser with compressed air. Collect this and make sure you are up to 2.5 oz. If you have not gotten to 2.5 oz. you can try to drain more from the system or decide that you system has lost oil due to leaks or other reason. The main issue if you have too much oil is increased potential for a compressor failure.
6. Replace the oil in the compressor with PAG 46 oil. Add the same amount removed from the compressor if it was over 2 ounces otherwise add 2 ounces.
7. Put R134a connectors on the R12 connectors.
8. Place gauges on the system and vacuum for at least 30 min. Turn off the vacuum and make sure the system has no leaks (holds pressure). If you don't have the gauges or vacuum, you can have an A/C shop do it.
9. Charge with 24 ounces of R134a.
10. Check the low side pressure and make sure it does not go over 40 pounds or 275 kPa. If your system is blowing out cool air instead of cold air, check for an overcharge condition by checking the temperature of the lines into the receiver dryer. If they're hot instead of lukewarm you have an overcharge condition.
At this point, you should have cold air. If you're sitting in the garage the air may feel cool instead of cold. If pressures are okay, take a test drive and see if it cools down.
Removing the Compressor
1. Put front end up on jackstands - but loosen front wheel bolts first so you can:
2. Remove front wheels.
3. Remove right wheel well liner.
4. Unbolt both ends of front sway bar. Use an adjustable wrench to hold bracket square so you don't break.
5. Unbolt the right side of sway bar from hanger.
6. Remove hoses and bolts from compressor.
7. Grunting loudly, carefully pry the compressor loose from the bracket. A very long, thin pry bar is useful.
8. Once you have the compressor lose, you should be able to get it out on the right side.