Hi -

I bought the car about a month ago - the AC is blowing hot air. Before I bought the car the PO told me that the AC system is in working order but it needs to be recharged.

The PO had the compressor replaced around 2002/2003 but he does not know what type of refrigerant is in the system...

I have a friend in the HVAC business and he can help me recharge the A/C system in the car but he'll want to know what's in there to begin with...

Question: how do you determine what's currently in the sytem - I've read here that you're not supposed to mix two different types of refrigerant...

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1987 Mercedes 300SDL; SOLD
1985 Mercedes 300D; SOLD
2006 Honda Pilot - wife's ride; 122K;
1995 Toyota Land Cruiser - 3X locked; 182K

All that you have to do is look at the charging connections, external threads is R-12 internal threads is 134. You AC friend should be able to determine this. The fittings are made deliberately different to prevent cross charging with different refrigerants.

unless you friend has access to testing equipment there is no real way to tell what is in there. Your car came stock with R-12, but many were converted to R-134a used today. Then again there are so many aftermarket mixes and blends touted as r-12 replacements that have all sorts of mixes, in them.

Since the compressor oils are rarely compatible between types of refrigerants, I would suggest that your friend overhaul the system and flush it thoroughly, replace the expansion valvel and charge with the right oil and R-134a, do the conversion now and save yourself the headache. Also have him install the proper fill port valves/connections.

You cannot go by the connections alone, many convert to 134 and never change the connections...why because they still have their old gauges and it's expensive to buy a second set. Also any conversion should have a label afixed to the compressor indicating that it has been converted and to what. Agian with all the aftermarket drop ins, you could have propane in your system as far as you know. Fix it right and start with a new clean charge.

Best of luck

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Stable Mates:
1987 300TD 310K mi (Hans)
2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee)

I would recommend that you do not convert to R-134a. You will just go from having a system that does not work to one that almost works. If it's already been converted, go back to R-12. I am currently in the middle of a R-12 "conversion" after having tried R-134a with very unsatisfactory results.

I agree, do it right. Flush entire system, recharge with R12.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

Agreed, R-12 is the best for your car and will work the best, just be aware that it costs a bunch and will continue to be harder to come by even if you have a 609 to buy it.

134a is a couple of steps down, I have it now in my 124 as the PO did the conversion, but there is an advantage to it, the system leaks slowly, not sure from where yet, but topping it off is well painless and fairly inexpensive and can be bought anywhere when compared to R-12.

On another car I converted from R-12 to Autofrost, a little better than R-12 and at the time the only EPA approved substitute. 5 years later still works like a charm.

Biggest concern is having compatible charge and oil or the compressor will go soon.
Cheers

__________________
Stable Mates:
1987 300TD 310K mi (Hans)
2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee)

Last time I bought R12 I paid a little under $12/lb for 6 cans. When R134a is selling for $9 a 12 oz can, that's no cheaper.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

Pete Let me know where you get your R-12, I can't readily find it in cans anymore and my price check today show 30lbs. Cylinder of 134a at $199 or $6.63 per lb. and R-12 is going for $477 (30 lbs.) or $15.90/lb.

If you got a cheaper source please share, I still need R-12 for my Jeep or it's also going to Autofrost at $7.12/lb.

Thanks

__________________
Stable Mates:
1987 300TD 310K mi (Hans)
2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee)

ebay. I'll try to find the source I used last. Even at $16/lb, R12 is cheaper when you consider skipping the conversion fittings, gages, maybe replacing hoses and the longer life of your compressor. You lose less R12/year because of lower pressures and less losses through hose porosity.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

What are some of the things that you've experienced with conversion to 134a?!

My friend recommended that I convert to 134a, so I'm curious about the disadvantages. I'm looking for a simple solution that will not be a pain to maintain in the future... (FYI - I do NOT use AC, it's just for my wife's convenience... hehe - I'm from the old country and the AC-on means that you lower the window a bit...

__________________
1987 Mercedes 300SDL; SOLD
1985 Mercedes 300D; SOLD
2006 Honda Pilot - wife's ride; 122K;
1995 Toyota Land Cruiser - 3X locked; 182K

R-134 is just not as efficient as R-12. When I had R-12, the a/c worked great. Better than any other car that I had owned. I converted to R-134 because I bought into the myth that R-12 was going to become unavailable. That was 8 years ago. It's still available, and at a lot lower price.

I was told that I would suffer some degradation in performance with R-134. What I found was that the a/c would not perform acceptably in temps over about 85 degrees. If I start driving on a hotter day with the car having been in the garage (ie: a cool start) the a/c performance is barely acceptable. But after the car has sat in the sun, its all over. You have drive for 20 minutes to get it even fairly cool. In stop and go conditions, performance is not close to being acceptable.

R-134 might work great in cars designed for it. The have larger condensers to compensate for the decreased refrigerant efficiency. But if you just charge up a R-12 system with some R-134 and compatible oil, I suspect that you are not going to be happy.

I have R-134a in my 300D and R-12 in my 240D. The R-12 system does blow a little colder, but the difference isn't significant enough for me to switch back to R-12. I would estimate that the R-134a system has about 80% the capacity of the R-12 system, but it is perfectly acceptable to me (in Denver). It may take the R-134a system an extra 30 seconds to start blowing cold after the car has been sitting in the heat. I did notice that the R-134a system could have done better in AZ last summer, but it was still adequate.

If I was redoing the system today, I would probably go with R-12, but I wouldn't bother to convert a working R-134a system back to R-12. YMMV.

Sounds good - I just checked the receipts I got from the PO and discovered that they had converted my AC to R-134a when he got the new compressor back in '02, so I guess I'm going to have my friend just recharge the system with standard 134a refrigerant and we'll see what happens... I'm guessing I'll stick with it (if it works).

Also, checking the LOW pressure fitting above the radiator further convinces me that I've got the 134a as the valve has the threads on the INSIDE...

Thanks for all the info...

__________________
1987 Mercedes 300SDL; SOLD
1985 Mercedes 300D; SOLD
2006 Honda Pilot - wife's ride; 122K;
1995 Toyota Land Cruiser - 3X locked; 182K