Heat wave here in So. Cal... Ouch. I had to aim my fan at my cable modem just to read this board; it drops my connection when it gets too hot!

My 300TD was converted to r134a at the end of last summer... The AC didn't work at all for years before that, and it wasn't very hot in October so the conversion seemed fine to me. And it is... if you're sitting in the front seats, and the temperature doesn't get above 85.

Yesterday and today made me decide I need to do something to improve the AC - either convert back to r12 or do some kind of upgrade (or both).

Searching the board, I found plenty of references to r134 -> r12 (re)conversions. I also found lots of talk on upgrades (bigger compressors, parallel flow condensers, better fans) but nothing apparently concrete on that subject (nothing from anyone that's actually tried it).

Parallel flow condensers and a better fan sounds like a worthwhile upgrade. Leathermang was talking about doing it in this thread:
Increasing Air Conditioner Reserve Capacity ?

Does anyone know how that went? Can you use a parallel flow condenser with an r12 system (it sounds like they're just meant for r134, but I hope that's not true; it would be nice to have the advantages of both!).

Anyone have any thoughts/comments/advice on this matter?

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'81 300TD Wagon 355k (Miss Diesel)
'83 300SD 180k
'84 500SEL 190k (Parting it out)

I have done the following to my 1984 300SD:

1.) parallel flow condensor (largest I could fit) with custom hoses and a little minor metal cutting to get it all in.

2.)auxilliary fan on relay circuit to compressor clutch, and adjustable temperature circuit as well, for fan engagement.

3.)adjusted evap temp sensor (small screw inside it) to ~34ºF (had it too low when I initially adjusted it and frosted the evaporator all the time).

4.)NEW R4 compressor (an ebay find, cheap), NOT rebuilt.

5.) Set up for R-12, but currently running "test" refrigerant (I'm not a proponent, so don't go there!). I put it in to check out the system for leaks or problems, but haven't found any problems, so haven't got around to evacuating, vacuum and recharge with R-12 (I have a small supply of R-12 hidden away).

6.)Replaced some pods when I had the dash out so I know all is well with air distribution.

7.) electric sun shade from an ~1989 560SEL. This has been the absolute best thing to keep the car cool and really helps "pull down" time!!!

8.)refilled the main fan clutch with 6000 cst silicone oil and shortened the pin under the bimetal strip to insure clutch engagement when warm.

Things still to do:

1.)window tint

2.) get the R-12 in it.

3.) recirculation mod of the switchover valves to the pods of the fresh air door.

In July at 105ºF going up the Sherwin Grade to Mammoth, the car was cool as a cucumber.

This heat wave is something for this time of year isn't it? If you want to talk about it email me your # and I'll call and share my tribulations of searching for the perfect walk in freezer on wheels.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

81Wagon, you don't need a Bigger compressor... just a good one in good condition....

Jbaj007, Tell us more about the electric sunshade... I have never seen or heard of it.... any picture available?

Can you post pics of your mods. Looks like an interesting project.

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N. Hodges
1994 S350
1987 300 SDL (for sale)

Sorry, I don't have pictures. I'll try on Friday to snap some.

The electric sun shade is a factory option for 1987+ long wheel base and coupes (different length rail for the coupe, but that's the only diff.). It fits on the standard 87+ parcel shelf and there are cut outs in the shelf already for installation. Wired to a polarity reversing switch (extra sunroof switch). One of the guys on the mbcoupes mail list did it and wrote it up so I found one at the wreckers and tried it. Section 68, subsection 600, # Q B6 6 68 8476 (odd part #, isn't it?) in the EPC for 87+ 560SEL.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

Do you know if one will fit an 87 300 SDL? Can you point me toward the write-up (thread) on the mb coupes site.

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N. Hodges
1994 S350
1987 300 SDL (for sale)

I would really like you to post the pictures of the mods you have done on here if you can.

It will be very helpful, since I hate having to ahve the Window open in the summer all the time. It gets to hot....

and will any R4 compressor work out? Can you tell me where I can buy some of those parts etc.... thanks

parallel flow condensor (15.5X24.75), all kinds of beadlock fittings and hose and great help available at ACSource.com and ACKits.com. Check the links section on this site: http://www.aircondition.com/

nhodges: The electric sunshade should be a direct fit to your car. If you remove the parcel shelf you'll see pre-perforations on the underside of the shelf for the shade and motor. It should be a drop in (assuming MB didn't bother to have different parcel shelf dies on the assy line, and I can see no reason that they would).

There are searchable archives here: http://www.mercedes.cx/560SEC/archives/

I believe it was a poster nemed "Talbir" or something like that, and it was within the last year, probably even more recent.

Edit: the posts are under "sharan bains" (also known as Talbir)

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

thanks once again...

jbaj007

Just installed the R134a in the 300TD. Parallel flow condensor, 14X22.5.

parallel flow condensor installed in a W123

All parts of AC system new. Evaporator was leaking which started all this. Had about 50% blockage of air flow on the evaporator.
Here's the link to that post

evaporator out of the 300TD

Heres the question. How much freon did your system take. Mine calls for 42 oz and the normal 80% of R134 for a R12 system should have it take 34 oz or so. It's taking about 30 oz. With that amount the vents are 35 degrees (outside 72) with the Aux fan on and an extra fan blowing on it. Did you find your setup took less?

Also. My pressures are running low. The manual calls for 22psi low and 265 high. I'm running 17 and 185. But the vents are 35 degrees. What are you running?

For everyone. I'll post the results of the parallel flow conversion with R134a as the summer progresses. I will try to set up a meeting with Larry Bible and do a side by side comparison. If the R12 is better I'll convert and we will have info on the parallel flow with R12.

Dave

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1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car

Thanks for all the info jbaj007! This topic seems to be a popular one here, so it makes sense (if you don't mind) to keep questions and advice in this thread so that everyone can read it :-). Bear in mind I have no experience whatsoever with AC so some of my questions may be a little basic (thanks again for helping and feel free not to answer if I'm asking too much!).

How did you get the custom hoses done? This seems to be the most troublesome part of adding a parallel flow condensor. If an AC shop did it for you, how much did it cost? How did you know what fittings/adapters you needed?


I plan on installing an electric main fan (variable speed depending on temp.) and may replace the auxiliary one if you think it is necessary. How much better is the fan you got compared to the stock one?

Did you have to take the dash out for this?

How cheap was "cheap"? my current compressor seems to work fine, do I need a new one? Will any R4 compressor fit into our cars, or do these things come in different shapes and sizes? Any recommendations?


Got that on my list too. Have you looked into the laws about tinting the front windows here in CA? I've heard different things, from "you can't at all" to "up to 88% is legal" to "as long as they aren't too dark you won't get a ticket for it anyway" ;-).

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'81 300TD Wagon 355k (Miss Diesel)
'83 300SD 180k
'84 500SEL 190k (Parting it out)

The compressor you need is an R4 "Light" made by Delphi, metric fittings. Its $225 brand new from ackits.com. I just ordered one today. If your R4 compressor is working AND does not leak, you can use the existing one.

Some of the comments made by Dmorrison bring us to this point: how do you know the system is still properly charged (dude, you are in Santa Barbara, it aint that hot there)? Seriously I know you have a wagon, and the load is higher than on a sedan.

You may have a leak. R134 needs to be properly filled to capacity. Its not nearly as forgiving as R12.

You've got a 20 year old car, you said it was converted BUT was this the only work that was done on the system? After pulling apart my 20 year 300D on Sunday, the O-rings are all dried up, the pressure switch was leaking, the front shaft seal was leaking a little. A couple of the hoses had bulges.

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84 300DT Puke Yellow. Totalled after 438,000
84 300DT Orient Red. 169,000 (actual mileage may vary)
2002 Explorer EB (wife's)

Any time it gets into the 90's I have to consider it pretty hot. Hell, it's midnight and it's still nearly 90 degrees in my house. Forget the car, I want AC in here .

Thanks for the info. I am going to stop by my mechanic tomorrow anyway, but as far as I know everything is running as well as it can. I guess we'll see....

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'81 300TD Wagon 355k (Miss Diesel)
'83 300SD 180k
'84 500SEL 190k (Parting it out)

81Wagon,
Don't even consider messing with the internal setting on the TXvalve.... they are about $25 new.....and remember he is testing a different refrigerant right now....just get a new one...and be sure it is the one for R12..... it takes specialized equipment to properly reset it .... and you don't have it....
Keep reading the archives on AC info..... someone told all about the P flow retrofit and told exactly the sizes of the custom fittings he had made....they are there somewhere....may have been GregS...

DMorrison,
when you said " Evaporator was leaking which started all this. Had about 50% blockage of air flow on the evaporator.
" did you mean you had blockage on the condensor ? (the one at the front of the car )....

On your pressures..... You may need to wait until it is hotter to determine if you have installed the correct amount of refrigerant...pressures are closely related to load... so at 72 ambient those figures may be ok...or at least may not be able to spot a problem without higher outside temps (load)...