The climate control system on my '86 740 is a disaster. The heater control valve is competely missing and the core is bypassed. Since it never really gets cold in Arizona It really doesn't matter to me at this point of the season. Maybe next year. However, as summer approaches I have no desire to fry in my brick, as 115 degree temps are not uncommon here in the summer. Here is what I have. A compressor of unknown make with a two wire connector on it. One of the hose connections is disconnected at the compressor and I found that the nut is stripped. The compressor therefore has had one nipple open to dust, dirt and the elements for who knows how long. The system has beed converted to R134, but since I have a 25 lb bottle of R12 I want to go that way for better cooling. I think at the least I will have to get new hoses made, have the compressor tested for fuctionality and leaks, replace the drier and expansion valve, and evacuate and maybe flush the system. My question is do I need to change the oil in the comp. or can a 134 set up work with R12. is there anything else I should know about as I go through the system??? Any suggestions on replacement of compressors and hoses and any tips would be appreciated. In the past I had had pretty good luck just getting an older compressor tested and resealed as opposed to going with a new compressor which can be very pricey.

thanks,
740man '86 740

I feel your pain! Sorry, but it's such a great ( bs ) line. But seriously, I have an "84 760 GLE w/ acc and I live in Montana. Beleve me when I say that I know what a pain the acc system is. Try making through 20 degree winters w/ that system working properly! As for fixing the ac in your ride know this:
1) If it's been open as you say,then the entire system ( hoses, condensor, etc ) are contaminated and as such will give you problems and may result in poor performance and/or failure.
2) Once a system is unused, especially in a dry area as yours, nearly every seal in the system is subject to failure becuase the lubricant is no longer present to keep them in proper condition. Hence, putting a new compressor may only be the first chapter in your education about ac ( ie, when the system is charged, it leaks everywhere and your now faced w/ an entire rebuild-you don't want to know about that! ).
I don't know how much you love your brick, but for the potential cost involved, you might want to consider a different brick.

Raidman,
I do love my brick. One of the reasons is I bought it for only $600 and it has a great engine! I did some pricing and I can do a new comp., Hoses and Orings, drier and expansion valve for about $400. I have the R12 and access to guages etc.
I have redone a few AC systems on other cars out here and it went pretty well. On my old Jeep Wagoneer I swear it was blowing snowflakes when I finished. I think I'll give it a shot, paying special attention to the seals. Thanks for the advice.
It should be an adventure as you say.
740man

R12 is VERY damaging to the Ozone layer...that's why R134 was substituted in 93. I just got the R134 conversion kit ($65) and will install next week in my 89 740.
go to a U Pull It junkyard, find a late 80' or early 90's 740, pull the A/C stuff off, intall in yours, do the conversion and be COOL!! really COOL!!
el Raidman