I finally ordered my AC compressor for my wagon (yay no more sweatin bullets) I know I'll need a dryer (whereever that thing is) but is there anything else I should need to know before tearing into the system? the 134 is gone and is just under vacuum, I need to order the dryer soon... Will I need to yank the dash out (please say no) for anything?

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hum.....
1987 300TD 311,000M Stolen. Presumed destroyed

Which car are you working on?

If you want to improve your a/c performance, this would be the perfect time to reverse convert to R12. You need to flush everything and replace the r/d anyway when replacing the compresssor. Simply do all this then put in 8 ounces of mineral oil, the new r/d and charge with R12. Due to decreasing demand R12 doesn't cost much more than 134 these days.

uhhh, where are you getting this? the stuff gets more expensive every year as supplies dwindle. I just paid over 100 bucks for a little bit of it to top off an early 90s fridge that uses R-12. If the car is already converted to R-134, leave it and simply fix the A/C.

The R-12, while better at making a cooler car, is not that much better than the R-134 to warrant changing back to an expensive and universally recognized environmentally harmful R-12 system. It sounds like hes starting from a non working system anyway, so either would be cooler than nothing.

If the system does not work, but its still closed, id run the car by an A/C shop and have them discharge it and vacuum the system out with the machine before you open it, just to make sure any remaining stuff is not vented into atmosphere, and that you don't have to work with any vapor or freon.

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This post brought to you by Carl's Jr.

yup. do not convert back to r12. we all know its bad for the environment. and 134 works fine. make sure the system is clean inside. any fragments from the old compressor will ruin the new compressor. don't forget all the o rings needed and read the instructions w/ the compressor. it may come prefilled w/ oil or not. may have the wrong oil in it, but probly has pag oil if any. they say not to mix oils.

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1984 300TD "MAX" 303K+ still going...
fast '70 Chevelle 200k+
home built Shovelhead chopper

It is that much better.

I converted to R-134a. Results were pathetic. Converted back to R-12 and the difference is incredible.

maybe so, maybe not. I agree that I thought it was better, but I also felt that R-134 worked just fine, so to each his own I guess.

At the same time though, this is like saying we should all go back to leaded gasoline because we thought the car ran better.

Its up to Aquaticedge to weigh whether the debatable but real gap of cooling efficiency between the two refrigerants outweighs the bother of switching back to an antiquated system that uses a NLA freon thats blatantly harmful.

If he's already on foot, jumping up and riding a donkey or jumping up and riding a horse would both be positives.

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This post brought to you by Carl's Jr.

It's not at all like that. Not even close.

The refrigerant and the system need to be equally "antiquated."

well, if it was converted to R-134, he would have different service ports, different oil, maybe some different rubber hoses. But yes, the majority of the system would be the same parts. He would have to completely clean it all out of the 134 lubricant and put in the different compressor oil. He would probably be doing all this anyway, but using an R-12 refrigerant system is antiquated as of, what, 1993? 17 years?

My point with the leaded gasoline remark is that whether or not its better or not, leaded gasoline and R-12 are both things that are no longer made in this country, and getting R-12 will only incur greater expense over time as supplies dwindle. Plus most A/C shops are less and less experienced with R-12, and now he will have to call and make sure that they can work on it, or have or can get R-12. On top of all that, the stuff is environmentally harmful AND he will pay more for it every time.

The question is really why?

You maintain that the difference is so much that he should do this. Ok, I respect that opinion. I am surprised that you had such poor results when you converted though. Maybe there was another factor.

My point is that I can drive along in an air conditioned car with either R-12 or R-134 in a hundred degree heat and 100% humidity and feel nice and cool and comfortable in the cabin. To me, the newer stuff performs just fine, can be serviced everywhere, can be recharged everywhere, and is less harmful than the R-12 if it leaks out.

Hes already half way there, he might as well leave it alone.

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This post brought to you by Carl's Jr.

I tried converting my 300D to 134a, I didn't like the performance and converted back to R-12 several years ago. Stick with R-12.

ok everybody pay attention to the original poster. he has an 87 TD... it's got all the same components that the newer 124's do. converting that to 134 is perfectly fine.
it's only on the older 123's and 126's that 12 is such a huge difference because of the crappy R4 compressors, and the pitiful tiny condenser in the cars.
the 124 series vehicles have a huge condenser, and a much better compressor with oil sump. I'd stay with 134, and get the aux fan working perfect if it's not, and get that new dryer (it's behind the driver's headlight by the way)
I don't know what killed your original compressor, but be SURE that if it failed catastrophically that you reverse flush the condenser and be positive any screens are free of debris.
this is critical for performance and longevity.
I'll leave the debate for and against the environmental aspects of 12 to the politicians. as long as it's available, and I do everything in my power to prevent it's discharge into the atmosphere, I'm going to us 12 in the older vehicles.
My 87 has 134,and it's IDENTICAL to the system in the 93 parts car I have, that came stock with 134. my 87 puts out 29degree air, and works great. I'll stick with 134 for now.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

The '87 was designed for the pressures and temperatures of R12, and R12 isn't that much more $$ as R134a has crept up in price so much.

If you have a good leak-free system, I suggest R12 for its better cooling with your installed condensor etc. Is the new compressor designed for R12 or R134a though? It is my impression that the compression ratio is different in the compressors, and you might be better off with 134 if it is the correct compressor?

The R12 advantages are more efficient, and colder temps. As you live in the humidity capitol of the country, I'd suggest R12 if it's leak-free.

The advantage to the R134a is that it is easier to find, and everyone knows the pressures necessary (although for an R134a converted '87 300TD turbo it's a bit of a swag).

(not an HVAC Tech or HVAC Engineer)

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Gone to the dark side

- Jeff

that's a good point mog, the compressor on the 87 has lines going straight to the coils, the 93 appears to have the same compressor (I'm sure it's not exactly the same) but the lines go into a pair of chambers mounted on top of the compressor... perhaps this helps the compressor somehow... it could be a muffler for noise, or it could be something to handle the pressure differences of 134... not sure.
all I do know about the pricing of the refrigerants is I just had to purchase a drum of 134 and I about fell over. last bottle I got was 89.00 this was 219... wow. huge jump. 12 went from 1500 to around 589... that's new prices, not the deals I've gotten on craigslist and ebay...

Ditto

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1987 300D (230,000 mi on a #14 head-watching the temp gauge and keeping the ghost in the machine)
Raleigh NC - Home of deep fried sushi!

In FLORIDA?? DO NOT bother with R134a retrofits with an older design, especially in a W123.

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1987 300D (230,000 mi on a #14 head-watching the temp gauge and keeping the ghost in the machine)
Raleigh NC - Home of deep fried sushi!

ok, your wagon in the sig is an 87, so it's a 124 with a large condenser and a modern (*not a stinking R4 gm...) IF you are SURE there are no leaks in the evaporator, you don't have to mess with the dash. before you tear out the system, have it leak checked and be SURE it's not leaking! it's NOT fun to replace that coil!!!
never leave a system under vacuum. unless you are done checking for leaks and you are wanting air to get sucked into the system. everytime you connect the hoses, or connect anything, vacuum will pull in trash.
I'd purge the vacuum with nitrogen and evacuate again, and then purge again with nitrogen and let it sit with 90psi of nitrogen while you decide what else to do. sitting at 90 will show you leaks also. as long as the temp remains within 50 degrees of where you set it, the pressure won't change much aside from leaks. so if it drops you know you still have a leak.