Hi, I've got a new receiver/drier, expansion valve and evaporator I'm installing in my 84 300SD.

First question:

The compressor works but is 8-10 years old. Should I replace it, too? Consider I am replacing receiver/drier now.

Second question:

Does 134 work well, even in hot climates like TX? When the system was previously working it worked really well even in 100 degree weather with 134. After this investment should I put R12 in it? Mechanic said it would be silly to do so because lines are set up for 134 and he said R12 is so expensive that if there is a leak in any of the work performed it will be easy to run through loads more money.

If you vote for R12, where can I get it? He does not have any.

Third question:

I've got the two A/C lines open with the airbox out of the dash. They were previously attached to the expansion valve. Someone warned me that a couple of days with the lines disconnected would ruin the entire system. Others have said not to worry, even for a week. Right now I've got fabric clipped to the ends of the expansion valve lines. What is your vote...would it be bad to leave those lines open for a week or so.

Thanks very much

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1984 300 SD 384,000 Miles