Dave, Wow ... four days... that was about my impression from others posts.... but WOW anyway....
I do not think a vacuum down the vents is going to help because that mess was on the other side of the fins from the vents...but I do think a pressure wash from the vent side through the fins might be helpful...
I just think I am too old to pull the dash... not into that kind of detail right now... LOL

Let's not forget my classic post:

vent temps with r-134a w123

I could be wrong, but I think I was the first on this board to do the parallel flow conversion in a w123. I'm going on my 3rd summer after the conversion and it still works great. One thing I always mention is that my auxillary fan is almost always on when I'm idling in traffic, so I wouldn't waste a bunch of time with rewiring the fan or whatever to get it to go on. Just replace the pressure switch with a new one designed for 134a and it will come on more often than you think it will.

Good luck,

GregS
'84 300D, 183k
'90 300CE, 174k

Greg,

I hope you meant the temperature switch and not the pressure switch.

Edit?

Eric

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

I've spent a couple days thinking about parallel flow condensers and this is what I've come up with...

I plan to use this condenser from ACSource.com (it should just barely fit; if not, only a tiny bit of cutting should be required).

Because the fittings are on opposite sides, and because my compressor to condensor hose seems to be on its way out anyway, I plan on having a new section of hose fabricated to come through the driver's side to the compressor (it'll still have to hook up with part of the old stock hose - I'll have that shortened with new fitting crimped on - because I don't think I want to mess with that weird double-hose fitting on the compressor itself).

Here's a quick before-and-after diagram I made up; does anyone see anything stupid/wrong I may have done? Any advice? Does it look like it'll work?

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

Diagram looks doable. Make sure a HP fitting for your quages is put on the red hose. What about your washer tank? Will the hose go under the sheetmetal or under the tank? You will have to make a hose for the passenger side fitting to the R/D. Getting the hose to bend is not easy. Getting the correct fittings welded together is how I solved it. Or you can cut the sheetmetal near the fitting and make a hose to the R/D. This is why I made the "manifold". 2 fittings per opening and some tubing TIG welding together. I am using stock hoses in the rest of the setup.
The purple hose is the manifold hose. Very expensive and would be a pain to reconfigure. I would suggest making your hoses to fit the manifold hard metal section. Otherwise fitting hoses to the compressor will be a hit and miss setup. Make sure you give the hoses support so you don't wigggle the fitting loose over time.
Metal hoses from the condensor to the R/D. I would suggest putting a rubber hose section in there. The vibration of the car could cause the metal hose to crack over time. The rubber section would absorbe the vibration.
Dave

__________________
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

Leatherman -

I'm not really much into debate, so let's just drop it. I'm comfortable with my understanding of a/c operational theory, I think you are too. We just don't happen to agree.

So I'll toss out one last comment, then I'm bowing out of this thread - there are already too many conversations going on in it! In your last statement you imply there is valving on both the inlet and outlet side of the expansion valve. That is incorrect - only the inlet side has any restriction. It contains a needle valve to meter refrigerant into the evaporator. The low pressure side of the valve is wide open; the entire evaporator is directly connected to the suction side of the compressor with nothing between it. So there is metering of refrigerant into the evap, but not out of the evap.

- JimY

Thanks for the reminder about the high pressure fitting; I've added it to my diagram so I won't forget :-). The hose should be able to fit under the washer tank; the tank hangs a couple inches above the sheet metal in that corner

I guess that part of my diagram wasn't entirely clear. The only parts that will be metal will be the same as your "manifold"... Just the part that comes out from the condenser to meet up with the stock hose to the R/D. Here's a new diagram of that specifically (hope you don't mind I used your very own "manifold" to make it up in photoshop ).




I don't understand you here. Do you mean hook my new HP hose directly to the manifold hose metal lines? I don't think it is possible. The $*&#@ thing is one solid piece, including the hose that comes off it:


I was thinking of cutting that hose in the middle and crimping on a new fitting and connecting that to the new HP hose (hopefully the hose is flexible enough to double back on itself). Hmm, though looking at it now it seems maybe I could just unbolt the other metal end from the oil pan (passenger side of car) and mount it somewhere on the driver's side instead; then I could hook the new HP hose directly to that.

The hose would still have to double back on itself though... I wish I could just hook the hoses directly to the compressor and forget that ugly manifold fitting altogether. Could I cut the manifold hose at the metal line and have a new fitting welded to that?

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

"hopefully the hose is flexible enough to double back on itself). "

You really need to do what ever is necessary to avoid this... even if it worked initially... chance are that at some point, either from vibration or age it is going to cause a restriction to your flow... a metal u pipe , even at the expense of the more fittings or joints will be worth the peace of mind in longivity and performance... that is one of those hidden things which 5 years from now would be hard to diagnose...

And of course the obvious evidence of this prudence is the lack of such items in the original car... if they needed a 90 degree bend in rubber then it was cast that way ( radiator hoses) ... not taking a generic straight hose and putting it into a relative sharp bend... and never into a hairpin turn...

Okay, thanks. I'll try to find some better way of modifying that ugly manifold hose line to connect on the driver's side. Hmmmm...

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

Isn't there a parallel flow condensor with both ends coming out of one side. That would seem to be soooooooooo much easier.

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

Eric,
Most/many do. http://www.acsource.com/index.asp?PageAction=VIEWCATS&Category=254

__________________
The Golden Rule

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

Well then, with all due respect to 81wagon, why is he adding complexity to the project AND using a parallel flow condensor that requires the plumbing job from he**.

I don't think you need to modify the manifold hose if you use a parallel flow unit with both ends on the passenger side?

Whats your thinking process on this?

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

Yes, but they're all smaller... The stock condenser is almost 17 inches tall and I was hoping to put in a parallel flow condenser that would actually fill up the available space (as opposed to a 14 inch tall one). The increase in surface area from the one dmorrison used and the one I hope to use is about 20%... I just figure more couldn't hurt :-).

Particularly when my compressor-to-condensor hose on the passenger side needs replacing anyway - might as well fabricate a new one that will fit on the driver's side instead... The only extra work that will be required with this over a smaller one with both fittings on the same side is 1) Drill a hole (no problem) and 2) modify the manifold hose line from the condenser to point to the driver's instead of passenger's side (hopefully doable!).

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

Yes, you would not want to lose the extra efficiency you get from the P condensor by using a smaller one than you can manage to fit in there.... Just keep in mind fluid dynamics when designing it...

After lots and lots of reading up on this when considering how to maximize my 240 AC... I found that this is THE RULE :

The Primary limiting factor in any ac design is AIRFLOW ACROSS THE CONDENSOR..... which is some coefficient of air heat transfer times the efficiency of your heat exchanger....etc...

So this is where you have to be sure you are maximized if you are to hope to realize any other improvements you have done to your system...

81Wagon,

I'm posting this for those reading that aren't quite up to the layout of the a/c on the 12 chassis.

The discharge hose (your description: compressor to condensor) is actually 2 pieces. A rather expensive hose/pipe assembly known as the manifold hose that retails for $450! and a shorter hose that is about $37 from the dealer.

Its a pretty wacky curve combination coming OUT of the compressor with that manifold pipe.

I now understand what you are trying to accomplish.

Take lots of pictures and when you are done we are all going to hit you up for a "kit".

Think this will help bring the vent temp down in 90 degree heat sitting at a traffic light? Lets hope.

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