R12/R134 question - PeachParts Mercedes-Benz Forum

kerry · #1 11-28-2014, 06:25 PM

I had the 6.5 diesel in my 93 Chevy pickup replaced at a diesel shop. (ForcedInduction's former employer). When I got the truck back everything seemed fine but the AC wasn't working. When I returned it they said they had forgotten to recharge the AC since it was discharged when replacing the engine so I left it with them to recharge. It was R12. Got a call from them today saying they had run into problems with their equipment when recharging with R12 so had converted the system to R134. How happy am I likely to be with this conversion? System blew nice and cold with R12. Are problems to be expected when converting an older system like that to R134? Will it be as cold? Will it be reliable? They didn't ask me before doing the conversion. I would have been reluctant to do the conversion since I seem to have recollections of people being unhappy with conversion when R134 first came out.

Idle · #2 11-28-2014, 07:03 PM

Some conversions are as easy as dropping in the R-134 and calling it good. On Mercedes 123's this is the case but with the 123 you must also change the expansion valve. Not expensive; sort of hard to get to, but that's all you need to do.

You might do better asking this on a Ford truck board and see what other owners who did this conversion ran into and what they had to swap out if anything. One thing in your favor is that they discharged all of the R-12, this is important in a conversion since you cannot just top off an R-12 system with R-134 as you will wind up will less cooling power than before.

I used to do this a lot for friends and found trucks the most successful of the conversions due to having bigger everything in the A/C department and a smaller cab area to cool.

They should have also installed new inlet and outlet valves or converted the ones you have so no one installs R-12 someday by mistake.

aklim · #3 11-28-2014, 08:34 PM

My Vette has been converted. I can't say I am thrilled with the crap in the system. Sure, we changed the orifice but I don't think the system was designed with R134A so it doesn't cool as efficiently. On a cooler day, probably little difference. In the middle of summer, different story.

I'd be pissed if it was done without telling me first. You have to get all the O-rings out and clean off all the lubricant and flush the system if you want it totally clean.

upshift · #4 11-29-2014, 09:00 PM

Sucks that they didn't get your approval, but if they did it properly by replacing the dryer and all o-rings, draining the old oil and boiling the system out, I bet you won't notice a difference with the r134

aklim · #5 11-29-2014, 09:02 PM

Quote:

Originally Posted by upshift

Sucks that they didn't get your approval, but if they did it properly by replacing the dryer and all o-rings, draining the old oil and boiling the system out, I bet you won't notice a difference with the r134

I'll bet on an older car he will since I did after the switch in winter.

kerry · #6 11-29-2014, 09:24 PM

Overall, I've been happy with their work. I can ask them what exactly they did for the conversion. My guess is that they did it correctly. I'll pick the truck up on Tuesday but it's not going to be hot enough around here to really test it for many months.

aklim · #7 11-29-2014, 09:34 PM

Quote:

Originally Posted by kerry

Overall, I've been happy with their work. I can ask them what exactly they did for the conversion. My guess is that they did it correctly. I'll pick the truck up on Tuesday but it's not going to be hot enough around here to really test it for many months.

Well, if you are happy, fine. I'd be pissed that you converted it without my say so. Sounds kinda shady to tell me AFTER THE FACT. Without knowing what went into it and seeing the receipts, I'd definitely be upset.

When it is done, you won't notice till the hottest part of summer. By then, that is your problem not their problem. This is no different from you asking me for a small tattoo and me adding a changing the damn thing to whatever I think it better.

Angel · #8 11-29-2014, 10:16 PM

As I recall, R12 and R134 work most efficiently at different high-side pressures - IIRC R12 systems normally work at a lower(??) high-site pressure than R134, so that you can just drop R134 into an R12 system, but it will not cool as well unless you replace the compressor (with one that works at R134 pressures) and the orifice/TXV/Expansion valve.
I also remember hearing of some guys who changed the evaporator(?) to a more efficient one to further mitigate the reduction in BTU available.

All from a fuzzy memory here. I always get my refrigeration cycle backwards...
(but I can design a mean heat pump from it

-John

kmaysob · #9 11-30-2014, 01:51 AM

Quote:

Originally Posted by aklim

Well, if you are happy, fine. I'd be pissed that you converted it without my say so. Sounds kinda shady to tell me AFTER THE FACT. Without knowing what went into it and seeing the receipts, I'd definitely be upset.

When it is done, you won't notice till the hottest part of summer. By then, that is your problem not their problem. This is no different from you asking me for a small tattoo and me adding a changing the damn thing to whatever I think it better.

he's getting a tattoo yea, he's getting ink done, he.asked for a 13 but they drew a 31.....

TylerH860 · #10 11-30-2014, 02:43 AM

Did you ask about Forced, keep in touch with him?

engatwork · #11 11-30-2014, 07:53 AM

I've just recently converted a 85 300D back from r134 to r12. It is about an all day job anymore that came out good. Also, just recently installed the Sanden kit on a 85 300CD with r134 and a p flow condenser and it seems to do just as good as the one on r12. Toss up which way you go if you ask me. Don't expect much out of the stock compressor on r134.

kerry · #12 11-30-2014, 08:52 AM

Quote:

Originally Posted by TylerH860

Did you ask about Forced, keep in touch with him?

I don't keep in touch with him but I did e-mail him before I gave the truck to the shop to do the work to inquire about their quality. He recommended them for the work. But that's the only exchange we've had.

Mike Murrell · #13 11-30-2014, 10:58 AM

You my not know for sure how this conversion is going to work out until hot summer weather returns. If you live in an area where it's cold one day and semi-warm the next and aren't pleased with it on those warmers days, you'll then have an answer to your question.

davidmash · #14 11-30-2014, 02:06 PM

I live in TX. My 190 was converted to 134 quite a while ago. At idle it does not cool well but I really do not remember if it did under r12 either. At speed it cools great. Keeps me comfy eve at 100+ temps. I have no issues with my system conversion for what ever that is worth.

kerry · #15 11-30-2014, 05:03 PM

It's good to know people have been happy with their conversions. I do have an additional manually switched electric cooling fan I installed on the truck since the 6.5 has a reputation for cooling problems. That fan might help with the AC also.