Speedtoys

I will be 'soon' replacing my AC compressor, condenser, and driers with new units, and a new rear expansion valve too.

In the case of the condenser, an updated parallel flow unit.

With those items removed, a vast majority of the old oil will be out of the system. Would a simple chemical kit flush of the lines and evaporator, be sufficient to go back to R12 on on the system?

I will also replace the soft-lines at the compressor as well.

I will have all new green seals, and the front expansion valve is already new as well.

The dual A/C system works well, except when both ends are in use, and R12 will get me more effective condensing in slow traffic.

joejoe

When I did my '86.5 (I have necessary equipment) I flushed everything twice. This was after compressor failure and since all rings and both expansion valves were to be replaced I wanted it stupid clean. A good flush (I use castrol) will evaporate fairly fast. Let a bit of used flush evaporate in a cup (or anything that will hold) and see if oil residue remains. Some will re-use product to flush again. I do not. One use and done.

Having everything clean (and oil free) allowed correct oil to be added to fresh system. This system has not been touched in 14+ years.

The Forgotten On

I would stay with R134 as you are upgrading the condenser and using a new compressor.

But if you are going to switch back you should be fine after replacing all of the soft lines and doing a chemical flush as PAG and mineral oils do not get along well in the AC system and form a goop that can cause parts to fail.

If you used POE when you did the first conversion you should be fine with a chemical flush as it is much more neutral compared to PAG when mixed with mineral oil.

Speedtoys

Perfectly answers my questions..thanks!

The Fixer

134A is more efficient than R12 from what i understand and more eco friendly (can't believe i said that)

134A is said to remove more heat in the same vehicle than R12 given the same amount of refrigerant is in the same system.

And when you need to top it off in a year or two (no system is absolutely leak free) you can simply swing by the local auto parts store.

But what do i know, i don't even have ac in my 928..

j.kenzie@sbcglobal.net

PAG oil is not recommended for retro fits, so you probably have ester oil in your R134 system. Ester oil is compatible with mineral oil, so I would flush your heat exchangers, change the oil in your compressor, and put in a new receiver-drier. Any leftover oil should not pose a problem. And of course add the proper amount of new mineral oil.
Good luck,
Dave

Nicole

I never noticed a performance difference after switching to R134. But I noticed a huge difference in my wallet whenever something needed to be fixed.

The Fixer

^This.

Speedtoys

..everything's already brand new, including some of the hard lines under the hood and car.

Sick of the tepid air in hot stop & go traffic.

Nicole

Even with R-12, the front AC lost some intensity when the rear AC was on. The system as a whole is not strong enough, but switching to R-134 neither fixed this nor made it worse. It is what it is: Weak.

dr bob

The rear system was an afterthought, pretty obviously, intended to replace a few ducts that would have need space from front evaporator to the rear of the car. Bottom line though is that the condenser is undersized for the amount of evaporator(s) installed.


Jeff, my stock compressor and heat exchangers deliver <20º at 1500 RPM cruising in 90º+ SoCal heat, once the heat-soaked car is no longer heat-soaked. With R-134a conversion done 15 years ago. Idle performance is not quite that cold, and of course a heat-soaked car or high humidity reduces vent temps. I'll be very interested in how your new system performs.

Way too many 'cheap' conversions have been done using a retail Castrol "kit", complete with a couple port adapters and a can of PAG oil. PAG is great for a perfectly clean system, but jellies when it mixes with mineral oil. Similarly, the original drier dessicants were not compatible with either PAG or POE, yet were left in, oil soaked, to accelerate the destruction of the compressor. So lots of reasons why these 'converted' cars have sucky performance. Since you are cleaning everything, resealing and replacing everthing, you'll get excellent results regardless of which refrigerant you select. I did like being able to cruise through Sam's Club for cylinders of R-134a for less than just a few 12oz R12 cans cost in the gray market. I still have most of that original gas cylinder remaining, plus a new sealed one for after the freon diaspora.