AC upgrades/improvements - Page 3 - PeachParts Mercedes-Benz Forum

erubin · #1 05-02-2004, 08:17 PM

jbaj007,

you wrote:
<>

I live in Mar vista which borders Santa Monica to the south. Could you tell me name and location of a "good A/C shop" for rebuilding A/C hoses?

Thanks

dmorrison · #2 05-02-2004, 09:11 PM

Quote:

Originally posted by leathermang
Oh Great ,Dave ,,,, now you have me worried that I need to take my 240 evap box apart and clean it... it spent most of its time in Arlington.... yours was really dirty.... can't afford that much blockage here in Texas....

Dave, did you do it yourself... if so how many hours did it take ?

You don't want to know. But Iv'e become very lazy since my daughter went to college and were empty nesters.
Im goin to say about 4 good days of work. If you want I can guide you. I did post the reassemblly of the dash when I installed the evaporator box. Do a search it might cut off some time for you. I had to "go back" a couple of times when I realized certian things were not done in the correct order.
The car has spent its life in Oklamoha and Texas. It's got to be Oklahoma's fault

If your doing it, replace everything. Evaporator, vacuum elements, Foam, rubber connectors to the elementsand clean the entire box. I did not replace the heater core, I hope I wonn't be sorry later, but It just did not seem to fail.
I have a CD of all the steps to the job in pictures, except the box rebuild and removal. I can make a copy for you if you want.

I do wonder if a vacuum attachment down the center vents might help a little. A small hose like used to clean computer keyboards. That might get the majority of the dust.
Or you can remove the dash, which is not a terribly big job and clean it installed in the car. That way you can do the elements and check everything over. Here is the unit in the car.

Dave

PS I now have a leak in the condensor R/D fitting. Glad I used R134a and not the R12 first. At least I hope it's fitting and not the manifold welds. I'll find out next weekend. Going on a cruise this week.

jbaj007 · #3 05-02-2004, 09:34 PM

erubin,
Santa Monica Radiator & Air Conditioning at 1537 Lincoln in Santa Monica.

Owned by the same family (the Perletter's) for 80 years.

Small shop with nice people; have always done right by me; hope the same for you. Take care, Bruce.

Really had to "dry fit" mine alot before I crimped and I still had forgotten (duh) the high side fitting. Luckily, adding it later made up for a short hose (my fault). Fit, fit, fit, fit again....then crimp.

leathermang · #4 05-02-2004, 09:55 PM

jcyuhn, The reference sites you posted really helped me get a handle on my objections to the original implication....

Remember that the Bennet site is making some generalizations when describing ac systems in order to cover many types...

The important section with regard to what we are discussing is the ' control systems' segment....

I believe you have taken some statements like " in many systems" and " most"... and extrapolated one of the statements in the opposite direction..... without taking into account the dynamics of the situation...

My first example of the logic here is this...

When you walk up to your car with it not running... you start the engine in order to start the compressor and produce cool air. Does it then make sense that when it has become too cold that you would cycle the compressor ON in order to reduce the temperature in the evaporator ? I say no...

Your temp/pressure charts are not applicable to the analysis of the dynamics of the overall system.

The last paragraph under ' system controls' is the important one... but it says it in a way which implies that ' cycling compressor and fixed orifice' have to be paired... not the case in our cars... we have a cycling compressor with an TX valve... and it is the dynamics in that block valve which are supposed to be controlling the temperature of the evaporator... when the temperature in the evaporator gets too cold the valve closes in order to spray less refrigerant into that space... thus lowering the outside temp of the evaporator...

at least this is what I dreamed last night.... LOL

and one last shot at the logic.... according to your charts... the refrigerant will have to be reduced to a certain temperature in the condensor in order to switch to a liquid .... in order for the liquid to be sprayed into the evaporator... and get the ' phase change ' effect upon which this entire operation is based... so how would this ' raising the temp by turning on the compressor' work enough on the OTHER side of the condensor to affect the control of the evaporator temperature ?... bottom line is it won't... the valve at the entrance and exit of the evaporator is supposed to take care of that...

leathermang · #5 05-02-2004, 10:00 PM

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

GregS · #6 05-02-2004, 10:27 PM

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

Eric Eliel · #7 05-02-2004, 11:57 PM

Greg,

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

Edit?

Eric

81Wagon · #8 05-03-2004, 03:59 AM

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?

dmorrison · #9 05-03-2004, 07:26 AM

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

jcyuhn · #10 05-03-2004, 10:26 AM

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

81Wagon · #11 05-03-2004, 11:15 AM

Quote:

Originally posted by dmorrison
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?

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

Quote:

Originally posted by dmorrison
You will have to make a hose for the passenger side fitting to the R/D. Getting the hose to bend is not easy. ... Metal hoses from the condensor to the R/D. I would suggest putting a rubber hose section in there.

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

).

Quote:

Originally posted by dmorrison
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.

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?

leathermang · #12 05-03-2004, 11:56 AM

"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...