Some time ago it was mentioned that Delphi H-6 compressors appeared to be for R-134A only. Some time ago I sent a question in to Delphi on the subject. Here is that exchange:

My original question:

"The Delphi H-6 air conditioner compressor data sheet indicates that it is for R-134A refrigerant only.

Is there a reason R-12 is not listed for OEM replacements (e.g. it is pre-lubricated with incompatable lubricants) ? Is the warrenty voided if R-12 is used after a complete flush/lubrication replacement ?"

Dephi'* response:

"We are unclear as to what you're inquiring about. This may be a compressor that was used in new vehicle production (indicated by a blue and white label on the compressor) or an older service compressor that was used for R-12 refrigerant systems.
However, if the label is orange and white, this is a service compressor that is compatible with R-12 and R-134a refrigerants.
The service compressors that do not have the orange and white label affixed to the compressor, were shipped with a mineral oil charge, for R-12 systems.
The compressors with the orange and white label are shipped without oil, and can be used on R-12 or R-134a. Lubricant will need to added to the compressor prior to its installation.
In any case, use of R-12 or R-134a will not void the product warranty, providing that proper air conditioning service procedures are used. (boldface mine).

Should, Delphi builds Harrison Compressors (or really Delphi took over many of the parts arms of GM - Guide Lamp, Delco Remy, Harrison Radiator) in the least major reorg of GM.

They now call the "HR-6" the "H-6" compressor but is essentially the same unit. Think of it like the 440T4 -> 4T60 naming.

Our 90 has been rattling for a decade now (started really early) and still works well. The major indication of a failing compressor if the pressures are right seems to be failure to cool well at stop lights.

All of the family cars (newest is a '92) are R-134A now and all work well in Central Florida (just needed it yesterday).