Assuming the system is healthy (any worn or damaged parts replaced), conversion involves the following steps:

- Flush all old lubricant from the components (except dryer, expansion valve, and compressor) using mineral spirits, followed by laquer thinner or brake cleaner.

- Replace joint seals with ones that are compatible with r134.

- Drain and flush lubricant from compressor. This is accomplished by hand cranking new lubricant through the compressor on a bench.

- Add specified amount of r134 compatible lubricant.

- Replace dryer.

- Button system back up. Pull vacuum.

- Charge system with r134. Should take about 80% of specified r12 charge. Though I have manifold gauges, after a conversion I like to charge to acceptable vent temperatures. That is, charge until vent temperatures don't drop anymore.

If you search through old posts, you'll learn many of the finer point of a/c repair. It's not difficult with the right tools. For your job you'll have to find a source of shop air for flushing and a vacuum pump. Without these tools, you're really doing a half-baked job and wasting your time.

__________________
95 E320 Cabriolet, 169K