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Condenser with integral high pressure hose?

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#1 · (Edited)
1978 450SL Air Conditioning Components Review

So I have been working my way through the air conditioning components of my 1978 450SL as I try to figure out why it won't work.

How's this for an opener...chafed high pressure hose! It originates at the compressor with a fitting...but terminates at the condenser, it's just soldered in!

Question: EPC shows this as a separate condenser and hose-- which I assume is a suprcede from the original.

Has anyone replaced this with a new condenser and separate hose?

The high pressure hose coming off the receiver drier is green and says Aeroquip. Is that original?
 

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#3 ·
Update: according to Tom at the classic center (a great guy by the way) the original parts are NLA and the supersede parts do not fit.

There you go, there is no combination of new factory parts that will work here.

That means removing the original condenser and having a new hose crimped on, not exactly rocket science. And even rocket science is not rocket science to a rocket scientist.

Score one more for originality....not even by choice!

I need to disassemble the entire system and take stock of what I have, then send everything out to have new hoses made. That entails removing the liquid line from the expansion valve-- and while I am in there, might as well replace the expansion valve.

The only thing keeping me from pulling the dash then is knowing the condition of the center vent actuators. If they are good, I will replace the txv by going under the dash- if bad, or the airbox is cracked, will pull the dash.
 
#4 · (Edited)
Like Howard Carter opening Tut's tomb...

First photo shows the condenser outlet with conical copper washer. This is the joint that attaches to the receiver drier (107 830 12 83).

Next photo is the receiver drier with switches in place. Top switch is the temperature switch (000 820 80 10), bottom is the low pressure cutoff (124 820 83 10).

The condenser looked worse than I thought and you can see the integral hose, this was pinched pretty bad-- would require a male flare fitting to be soldered on if I were going to save it, but given the condition of the fins and the fact that it would need to be flushed I'm going to go with a Behr replacement. The Behr actually has a male flare fitting at the upper right of the condenser, to which a separate hose mates.

Here is a photo from ECS' web site showing the male fitting- this is an Original MB part, but I imagine it's made by Behr (I don't know).



Orignal hose was Codan, from Denmark, which is still around today. The end is what I would call a 45 degree, but Mercedes calls a 135 degree hose.

The hose ends shown in EPC are actually Eaton Aeroquip field-installable hose ends-- not crimp-type. These can actually be installed with a vise, a set of vise jaws and the correct lubricant. All the hoses in my car have crimped-on fittings, so perhaps the Factory is offering a part that's a field replacement given that other parts are NLA? In any event, the price of the fittings from an Aeroquip supplier is about a third of the Factory, but the price of crimped fittings is a fraction of that and the assembly more repeatable.

I ordered the Behr condenser 0008350370 which is actually an earlier model than that specified for mine (supersede to 107 830 12 70). When it arrives I'll compare it to the original and see if it works, I expect it to be identical except for the detachable hose.
 

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#6 · (Edited)
Today's project was a big one. Removing the AC compressor and suction hose so that I can source replacement hoses and a new compressor.

Also removed the expansion valve, liquid line and rubber suction line. You veterans are not kidding--this is one of the most difficult things short of dropping the engine that I think one can do on an R107.

The day began with removing the steering wheel and instrument cluster to gain access to the expansion valve. I used the Factory pullers, this came out in about thirty seconds.



I thought I was going to have to remove the stalks, but there is a plastic piece at the bottom that comes out, allowing the panel to clear the cruise control stalk enough so you can disconnect the electrical connections and oil line.

There's a plastic cover for the cannon plug that covers the female pins, this came off! Fortunately none of the pins came out of their holes. . . I held the whole thing together while I figured out how to reattach the cover.



Once the panel is out it's pretty clear where the expansion valve is located. It's right there in front of you. . . covered not with butyl tape, but what appears to be a custom butyl conformal coating. . . the only way to expose the flats of the fittings was to scrape it off with a plastic scraper and dissolve it with brake cleaner.



Nasty, nasty stuff, made much more difficult by doing it in the inverted Yoga Position with your head just outboard of the brake pedal. ( I didn't remove the drivers seat for this operation.)



The above is a better shot of the expansion valve, showing the blue liquid line.

Finally after about an hour of scraping enough of the stuff was removed to allow a counterhold on the flare nuts so that the copper pipes of the evaporator are not bent. To separate the TXV from the evaporator required a 24mm flare wrench on the flare nut and a 17mm wrench on the body of the valve itself. . along with a pair of two foot cheater pipes to generate the torque necessary to separate these. I inserted the pipes through the gauge opening- the copper tube can move a little to allow you to line up the wrenches.

The suction line came off a bit easier, it uses a 27mm and a 23 (from memory). The Compensating pipe came off with a 17 with no counterhold (you could use a 12, thanks Roncallo!) The sensing end is a coil of tubing that is clipped to the outlet pipe of the evaporator- there is a half pipe shaped channel on the outlet pipe, the coil goes in there, then the clip holds it down.



You can see the filter screen that is in the inlet to the TXV.

With that out and the pipes cleaned of as much goo as I could tolerate, I tackled the compressor. I am grateful to user cwmoser and this thread: http://www.benzworld.org/forums/r-c107-sl-slc-class/2357665-ac-compressor-replace-ac-delco-15-a.html which reminded me that I needed to buy a harbor freight long 6mm hex driver to get the forward allen screws out.

I don't have a lift so dropping the subframe wasn't really an option. . .I went the radiator removal route. The fan came out with four 10mm headed screws, they aren't M6, they are a lot bigger, must be unique. Once the fan was free I removed the shroud, a pair of 8mm self-tapping screws at the top and the bottom just held in by clips. One spring on each side holds the radiator in.

I drained the radiator of coolant, disconnected the two trans cooler hoses, the upper, lower and overflow tank hoses (large and small) and removed the piece of black plastic trim under the radiator so I could get a floor jack under there. Using about an 18" long 4x4 to distribute the load, I carefully jacked the radiator up and out of the car-- it was sticking pretty tight on the rubber blocks on either side- these had to be pried inward to allow it to move.



On my '78 there are five bolts holding the compressor bracket to the engine-- three M8 with 13mm head-- one obvious one with a spacer in-line at front bottom, and two holding the rear of the bracket to the engine that were only accessible by jacking (and properly supporting with jack stands) the car and using a 3/8" extension with a universal and a 13mm socket to remove them.

I had to rotate the engine with a 27mm socket to get the notch in the harmonic balancer to line up with the lower M8 allen (6mm internal wrenching feature) so I could get it out. I sprayed COPIOUS PB Blaster on these screws-- I hate the smell of that stuff but it really works wonders. I put as much axial load on the hex bit as I could to hold it in the screw head-- then used the cheater pipe to CRACK the screws loose. They were on there with some serious torque.



After a ten hour day of this, the compressor was out and on the floor. This thing is HUGE! I read somewhere that at 4000 rpm it will put out as much as 42,000 BTU. That is three and a half tons, enough to cool a three bedroom house in certain climates. Way overkill in true M-B tradition!



Tomorrow. . . putting the power steering pump, radiator and belts back, reinstalling gauge cluster and wheel so the car can be driven while I order the parts and plan out the reinstallation. . .
 

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#7 ·
I just finished reading your thread on the condenser and compressor replacement. Very instructive.
Great pics. Did you finish your project? Sorry you didn't seem to get much help with your questions. I had many of the same questions and more. I believe the original condenser on my 280SL was replaced with one salvaged from any early 450SL but I'm not sure and have no part number. Were you able to determine what the difference was between the 000 835 03 07 condenser you used and the later 107 830 12 70? Did you reuse the conical copper washer on the attachment of the drier or do you have a part number for that washer? Was the attachment fitting to the top flare connection on the condenser that you referred to PN 0009971668? Was there any o-ring or other seal used on the flare connection? Is it a 3/4" flare? Where did you source the Behr condenser? Thanks for any help you can provide.
 
#8 ·
Don, I'm picking this project back up this spring, just ordered a bunch of parts including new aluminum compressor, txv, r/d and sent the hoses out to be restored with barrier hose.

The difference between the original condenser and the one I ordered is that the original one had an integral hose. The replacement (which is actually the earlier part) has a 3/4" male flare fitting on the side rather than the hose attached.

I have ordered new copper conical washers from Pelican and will fit these at all the junctions, there's no harm that I can see. Numbers like 000 835 65 98 for the 13 x 7 mm washer, for example-- of course the part number will vary with the size.

I have figured out that the early cars used the red aeroquip hose with the screw-on fitting. At some point the Factory switched to crimp-on fittings, which is what I have in the car.

Some Porsche friends are having the red aeroquip hose reproduced: http://www.early911sregistry.org/forums/showthread.php?123411-Red-fabric-AC-hoses

EPC doesn't show what I have, I bet an original parts book would though.

The number you mention, 000 997 16 68 is an example of one of these screw on fittings. Here is a photo of the part at ECS.



Hope this (belatedly) helps, I will be more active on this thread as the project moves forward!
 
#9 ·
Hmm hmm hmm parts flowing in. New aluminum compressor, barrier hoses, new TXV, copper seals, switches, prestite tape, PAG oil (I may switch to POE). Still missing the receiver drier.

I am going to use 134a. The TXV is specific to this refrigerant. I am tempted by 152a but I read the SAE paper (I am not an engineer, but I can read) that said that the motility of the refrigerant oil through the system may not be as high as either R12 or 134a. Which makes sense given its much lower molecular weight-- an equivalent charge has about half the mass of R12.

Stay tuned for the bloody knuckles portion of this DIY, coming this spring!
 

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#10 ·
Crowfoot wrench sizes for assembly: 19 (liquid line to txv), 22 (liquid to r/d, manifold high pressure to condenser x2), 27 (evap to suction, suction to manifold low pressure).
 
#12 · (Edited)
The beauty of ebay...putting professional tools in the hands of amateurs like me! With this I can not only charge but measure the vacuum in microns and also measure subcooling (and superheat, but this is a txv controlled system). This will allow me to measure the ideal refrigerant charge for a 134a conversion with no guesswork!
 

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#13 ·
Wow that is rather snazzy! I purchased my set from Harborfreight which was cheap. It does the job but I would not want to be a pro with my kit. Point is I maybe regass a car every 2 years so can not really justify going all out on the tools.

The reason I decided to do it myself (the amateur) is because I found the local professionals lacked any form or basic trouble shooting skills and kept coming up with illogical stories which involved me spending more money without receiving any assurance or in fact a working AC. Nowadays there is so much information available you can be a pro in a weekend. I know there are people the completely disagree with me so let's say it this way:

- 3 so called pro's could not (or were not willing to) fix my AC.
- I however could find the leak. I could fix the leak. I could re-gass the system safely and finally the system has been working flawlessly for 2 years+

Anyway - rant over - Good luck with your AC seems you have the situation fully under control!
 
#14 ·
Thanks J5 I am going to need all the encouragement I can get!

It's a Fieldpiece SMAN3, which is basically a two port digital manifold with an integrated micron gauge and a pair of thermocouples that precisely measure temperature.

I considered going with the basic setup which is fine in 99% of cases. But I want to be sure I get a vacuum of 40 microns before I charge (an old Porsche HVAC mentor, Jim Sims, formerly of the Los Alamos National Laboratory, insisted on that level) which means using a Micron gauge. A decent micron gauge is a couple hundred bucks, so by the time you add that to the manifold and hoses I was money ahead with this eBay purchase.

The really neat thing is the thermocouples and the built-in pressure/temperature database. To measure superheat, which is the temperature beyond the boiling point of the particular refrigerant at a given pressure, you clip one of the thermocouple leads to the outlet of the evaporator, and then set the correct refrigerant using the buttons. You can see in the photo above that I have set it to R134a. The box then automatically measures the difference between the measured temperature and the "ideal" boiling point from the p/t chart. You want the refrigerant to continue to heat up after leaving the evaporator-- if the temperature is too cold you run the risk of slugging the compressor with liquid refrigerant.

Subcooling is similar, except you're measuring how many degrees cooler than the boiling point the refrigerant is as it leaves the condenser. The concern is that if it's too cold, liquid refrigerant could back up into the compressor, destroying it.

So by looking at superheat and subcooling you can tell if the refrigerant charge is too much or too little. Suppose that 10F is the right amount of subcooling-- for measured values below this number refrigerant can added until the target subcooling is stable at that number.

And of course only the subcooling method will work for a system controlled by a TXV, like ours is.

Now I need some REAL HVAC technicians to chime in! :)
 
#15 · (Edited)
The resssembly begins...got the manifold back from plating, insulated, compressor mounted to the bracket, and the whole thing in the car.

I have the "third style" bracket so no modifications to the bracket or the compressor were required.

"While I was in there" I determined to change the water pump and thermostat, cheap insurance while the whole front of the motor is accessible.
 

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#16 ·
Got the system assembled this weekend...a very time consuming job.

Starting point was the evaporator core- the TXV mounts to this. I was thankful I had cleaned all the insulation off these parts when I removed the old bits. It made installation easier.

Notice I didn't say "installation a breeze." Any job that requires you to remove the steering wheel and gauge cluster and lay inverted in the car with your head next to the brake pedal is not a "breeze."

The valve went in easily, had to counterhold it to tighten the flare nuts.

I used Nylog blue (HFC-compatible) on everything. Used copper flare washers where I could, but the modern aluminum fittings don't really need them.

I had Griff fabricate a short hose to run from the manifold to the condenser. Remember from the thread title, my original condenser had an integral hose. This was a piece 16" long with 45 degree female flare fittings on the ends, clocked at 6:00. I didn't think I would get it right on the first try but I did.

So...when it was time to pull the vacuum...out comes the new pump, changed the oil to JB black gold (which is transparent) and started it up, connected to the center port of the SMAN3.

Unfortunately when I would pull a vacuum (got down into the 27s) then close a valve on the SMAN, the vacuum wouldn't hold. Now, if the car can hold a vacuum but it goes away when you try to valve it off, that means the valve is bad.

So I ordered a $30 kit to service the valves on the SMAN. It comes with new brass stems, o-rings, seats and knobs. Once that's done I will repeat the test.

I am also going to get a tank of Nitrogen for a pressure test and sweep, this should connect to the manifold directly.

When this is over I will know a bit more about HVAC! It's been fun, but time consuming, so far.
 

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#17 · (Edited)
Finally got the system charged.

Found a few leaks- I charged the system with 400psi nitrogen, up to 350psi, then used soapy water to look for leaks. System held pressure, maybe it ticked down a couple tenths, but the gauge hoses aren't perfect.
 

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#18 ·
I used two and a half 12oz cans of 134a.

Original charge with R12 was 1kg or 35.27 oz. R12 molecular weight is 120.91g/mol. R134a is 102.03g/mol. Divide the smaller number by the bigger one, R134a is 84.3% of the density of R12, so you use less mass for the same number of moles of gas. So 35.27oz x 84.3% = 29.731oz of R134a as an equivalent charge.

I rounded it to 30 oz or about 2.5 cans. I used the scale I bought to balance the Porsche pistons and rods to weigh out the refrigerant, this worked fine.

51F vent temp is great, not perfect. I'll see if the charge holds then will start tuning the refrigerant level for coldest temps.
 

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#19 ·
Still dissatisfied with system performance, can't do better than 60 Degree vent temps

I charged with Envirosafe. Put in two cans

It's NOT R290-- the PT charts are different. They tell you ES is 6 oz for 1 pound of R134A.

R12 MW= 120.9, R134a MW= 102. So 840g of R134a to equvalent 1Kg R12.

6oz = 170g which they say is equiv of 1 pound R134a = 453g. So that's 11.13 oz ES or about two cans once you take into account the purge.

ES PT chart suggests saturation temp of 31psi at 0F and 173PSI at 129F.

Can't measure superheat because it's not easy to get at the evaporator outlet (it's under the dash) and the TXV will continually adjust refrigerant flow to hit target temp. Best place to measure is on the suction line above the manifold, the low side port is right there anyway.

But you can measure subcooling-- and there's a convenient spot where the refrigerant exits the condenser right before the receiver drier.

High side pressure tap is on the manifold before the condenser, not ideal. Ideal would be to have a pressure tap right before the RD in the same spot. But I'll try measuring subcooling there-- about 10 degrees should insure the ES stays liquid all the way through the TXV.

IGNORE the superheat and subcooling readings, this is the internal R134a PT chart, not the one for ES. Which is not the same as R290 by the way.

Will report back.
 

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#21 ·
Epilogue:

I had changed over the TxV to one designed for R134a, as shown above. For whatever reason, whether it was the wrong charge, or more likely, too much oil in the system, I couldn't see better than 60 degrees vent temp with Enviro-Safe. The SMAN3 was showing 31 psi on the low side, and high side pressures of 129, with 10 degrees of subcooling measured at the condenser outlet, but it still didn't cool worth a damn. In order to change state in the evaporator, at 0C the enviro-safe MUST be at 31 PSI or less according to the PT chart. But for whatever reason, probably related to the TxV itself, liquid wasn't getting to the evaporator and boiling.

I made the decision to take the car to a professional. But not just any professional, I needed somebody with the equipment, experience and the fortitude to work on a car built during the Carter administration.

I took it to K & W Auto Radiator and Air Conditioning, out in Queens, hard by the Jamaica Center station. This provided a convenient way to drop the car off and pick it up later. Kirk, the owner, has been in business for 52 years, he took over the place from his father.

I explained my problems, he understood immediately. We discussed superheat, subcooling, TxVs, R12 vs. R134a, refrigerant oils, receiver driers, barrier hoses, butyl tape and the recent resurgence of the New York Mets.

He drained my system and charged it with R134A and now I have 47F vent temps. The Unwired Tools climate control system actually works, it actually closes the center vent after a few minutes to DECREASE the interior temps.

On we go. . .
 
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