You will be much better served to stay with R12. If you don't already have a 609 cert so that you can buy it, google 609 certification and take an online open book test for $20 or so and you can purchase it for about $15 a can off ebay or $30 at NAPA. You will be much better served than a 134 conversion.

BTW, the 250 is not the same car as a 280. The 250 is a small bodied car, while the 280SE is a big bodied, car, I think a 116 as opposed to the 114 or 115 series 250 car. An underdash unit is an aftermarket unit and should be easily transferred though.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

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