I have a good Seiko compressor from a 1994 940 (I blew up the evaporator when charging it but the car is only driven in the Winter and no A/C is needed, pretty dumb huh). I would like to put the Seiko compressor on a 1991 740 which has a bad compressor (very leaky shaft seals). I converted the 740 to R134a refrigerent back in 2003. The instructions from Volvo about the R12 to R134a conversion say to drain the compressor oil and replace it with ester oil if the compressor is being replaced. The old compressor does have a drain plug but I can't find the drain plug on the Seiko compressor. So, can anyone tell me how to drain the oil on the Seiko please? If I don't need to do this, should I add any ester oil? I don't know how much oil I lost when I blew up the evaporator on the 94 940.

Here's a picture of the instructions of the R12 to R134a conversion I used back in 2003 when I did the conversion on the 740:
http://www.brickboard.com/IMAGELIB/volvopic.htm?js_link=1&id=11117

Here's a picture of the compressor nameplate on the 1994 Seiko compressor:
http://www.brickboard.com/IMAGELIB/volvopic.htm?js_link=1&id=11118

Thank you.
--
Mine: 3-940s running, 1-740 and 1-940 parts cars, and 3 John Deere 630s, dtr1:3-940s, dtr2:2-740s