My 1970 Sedan DeVille. I can't get my AC to cool the car.

[Cadman-iac]

   I don't want to hijack your thread Stu, but I have a question for Greg.

  I'd like to clarify this in my mind.  I'm not sure what design condenser Stu is installing, so I'm not clear on what you're getting at.
  Which design do you think is the better one, the serpentine design, or the parallel flow design?
I was under the impression that the serpentine design was better, (From some of your posts on other threads).
I'm currently working on my wife's car, and trying to get a serpentine design condenser that's not damaged before I remove it from the box. (Long story, see my thread about things changing yet remaining the same).
  Thanks for your clarification.

Rick

["Cadillac Kid" Greg Surfas 15364]

Richard,
First let me say that there is VERY little "new" in the realm of heat transfer devices.  Parallel and Serpentine Refrigeration condensers have been since the late 19th century and are still being used WHERE THE ENGINEER FEELS THEY ARE APPROPRIATE FOR THE SYSTEM IN QUESTION.
That said, when the Engineers at Frigidaire or Harrison (kind of a blending of minds) designed the Cadillac AC systems, namely in the Automatic Temperature Control (ATC)  era, they thought about  all the components they were going to use and the range of conditions they wanted the best possible operation for the finished system.
They chose a serpentine circuited condenser for the reasons I discussed earlier, and IF you want your un modified ATC system to do the same stick with what General Motors paid Millions of research dollars to determine. Serpentine.
Greg Surfas

[Cadman-iac]

  Thanks Greg,
I appreciate your help. The car in question is not a Cadillac, but is a GM vehicle with the ATC, an '01 H body Buick. It came with a parallel style condenser, but the unit I received from the parts store is a serpentine design. After reading other posts you have made, I thought this might be an upgrade. Would that be correct, or should I look for the parallel style instead?

  There's something else I'd like to know about if you don't mind. The original condenser in my 56 Cadillac is definitely a serpentine design, but it looks like it's made with 4 channels. The exterior of the tube appears to have been shaped so that it has multiple contact points when the halves of the tube are welded or soldered together, forming the 4 channels, making it stronger.

The replacement condenser I got for the wife's car has very small indentations in the tube, I'm guessing from the machine that formed it. I don't think it's got multiple channels in it, I hope.
Do the new serpentine condensers have just one channel inside the tube, or do they make them with multiple channels? Wouldn't multiple channels be hard to clear if one becomes plugged?
And if a serpentine condenser has multiple channels, such as the 56 design, would that just make it a parallel style with longer channels, just less of them?
I apologize for all the questions, I'm just trying to understand how the designers were looking at this, and make sure I don't accidentally mess anything up.
  Thanks again for helping clear this up in my mind.

   Rick

[V63]

The whole industry has gone to parallel flow condensers🙄
And the whole industry has gone to fuel injection despite those that might prefer a carburetor.

In a perfect world we could still buy a shiny new VIR for $39
and A new OEM A6 for $99 then juice it with R12 at .79 cents a lb.

but THAT ship 🚢 has sailed !

I For one am exhausted with Pathetic excuse for OEM rebuilds at ridiculous prices and the remaining parts just plain obsolete 😖 And then there is the refrigerant 12 that is effectively obsolete as well.
So yes , if all the above was not reality today,  I might have limited enthusiasm for work arounds.

While it's global warming outside and the sky is falling ...I just want an air conditioner to actually perform and I have utilized such modifications with desired results☺️

We can view the glass 1/2 full or 1/2 empty.

 

["Cadillac Kid" Greg Surfas 15364]

Richard
"Parallel and Serpentine Refrigeration condensers have been since the late 19th century and are still being used WHERE THE ENGINEER FEELS THEY ARE APPROPRIATE FOR THE SYSTEM IN QUESTION."
Although it too is a simple refrigeration cycle the 1956 was substantially different in its refrigerant flow characteristics and the condenser was designed, again to maximize performance over the intended operating range.
I don't understand your question regarding the construction of the '56 condenser but perhaps construction methods at that time dictated that format?
If the depressions along the tube you are talking about are continuous along the entire tube length, Internal flow enhancement of heat transfer is suggested.
I have never said that R-12 systems are inherently superior to R-134a systems.  It is only that the flow characteristics of R-12 and Mineral oil and R-134a and PAG or Ester are different enough to require compressors, expansion devices, evaporators and condensers that comply with the refrigerant/oil to be used.
R-134a/PAG (or Ester) oil mixtures work fine in systems designed for them, but when used in R-12 systems using all original components, they do not provide the oil return necessary to maintain the longevity desired.
As far as rebuilt A-6 compressors, I stand by what I have said previously that I have never had a Delco Rebuilt from a reputable source (direct from AC Delco parts) arrive "DOA". They are very stiff initially but by filling the compressor with the 5-1/2 ounces of oil, rotating it several dozen times with it in its mounted position, then before engaging the clutch, charging the high side of the system with enough to bring the pressure in the oil sump up (it is on the high side of the system) again rotating the compressor 20-30 times to fully circulate the oil THEN engaging the clutch, the seal and the bearings are fully lubricated.
NONE of my cars are "factory perfect". I can do what ever changes to any of their systems that I feel would be productive, but ALL the ATC systems are factory correct.
Because that works best for me.
Greg Surfas

[Scot Minesinger]

The single in series serpentine tube is obviously going to the best at oil return.  There is no place for the oil to accumulate undisturbed by the flow of refrigerant.  A parallel flow with manifolds on either side, like the one installed in Bernie's Cadillac does have places for the oil to rest and not be returned to the compressor, however the heat transfer was better.  Hopefully the extra oil I added insures longevity for that original 1970 A6 compressor, now operating on r134.

I was thinking, what if two 1970 serpentine condensers were installed in parallel, which would reduce pressure drop through the condenser heat exchanger surfaces?  That would double the heat transfer surface and offer no place for the refrigerant to settle without refrigerant flow driving the oil back to the compressor, albeit at less velocity and pressure.  This would require minor mounting modification work and two "Y" shaped fittings or "reverse return" fitting arrangements.  This would completely eliminate the concept that the condenser required more surface area for r134 to effectively cool.  Alternatively, the two condensers could be piped in series, thereby increasing pressure drop through the condenser.  Obviously, this guess work type of engineering is not ideal, but if it got the job done of utilizing r134 which is inexpensive and recoverable very easily then it would be worthwhile.

Thoughts, has anyone done it?

["Cadillac Kid" Greg Surfas 15364]

To correctly provide the correct solution for any heat transfer device requires more than just adding "things" together.  Heat transfer starts with just how much heat (per unit time) you need to transfer, whether this is for condensing, evaporating or just steady state flow. Then the area (in the case of air to fluid) for air flow that is available is determined. Then the pressure drop (on the fluid side) needs to be determined which leads us to the last two factors to be determined.
The necessary heat transfer coefficient which is determined in part by the internal film factor which is in part determined by the fluid characteristics (viscosity, etc.) and the velocity through the tubes.
That then in effect sizes the tubes.
Air cooled condensers are sized so that by the time the refrigerant has passed through the tubes it has condensed into a liquid, and in fact several of the lower tubes are intended to be liquid filled  to add a few degrees of sub cooling.
Serpentine in parallel would drastically change the internal film coefficients by cutting the velocity in half and in effect reducing the heat transfer. Slow moving liquids would form what amounts to an insulating wall on the inside of the tubes.
Serpentine in series would mean you are trying to force a very liquid rich refrigerant mix into the second condenser which, again changes everything.
Greg Surfas

[Cadman-iac]

 Greg,

    Let me start again and explain what I'm trying to figure out. 
  My wife's car has what I think is a parallel style condenser in it from the factory. (See first two pictures, you may have to zoom in to see what I'm talking about).
The reason I believe this is because of how the entry and exits are "manifolded" basically where they enter the actual core of the condenser.
There's some 20 to 25 or so tubes that go from the inbound side manifold to the opposite end of the condenser and back to the outbound manifold. This gives the refrigerant and oil 25 paths to follow from the point of entry to the point of exit.
My understanding is that if any one or more of these 25 tubes that traverse from one manifold to the other should plug up with debris from something in the system, it's virtually impossible to apply enough pressure as you're cleaning/ flushing it to get the blockage to pass through and clear the tube. Your pressure simply takes the path of least resistance, leaving the blockage in place.
However with a serpentine design condenser it's a single tube from one end to the other, making a blockage much harder to occur, and cleaning/ flushing much easier.
Am I right in my thinking on this?

  But I guess the main question is, can I replace the original parallel style condenser with a newer serpentine design, or am I defeating the effectiveness of the system by doing it?

On a side note, I didn't ask for a serpentine condenser, that's just what the parts store sold to me for this application. I thought I lucked out when I saw that. Unfortunately it's also a Chinese manufactured part, and boxed by them. As I mentioned in my thread, their cardboard has the tensile strength of single ply starched toilet paper, so the part doesn't stand a chance in shipping.

I only mentioned the 56 condenser design because it looks like a serpentine style to me, with a twist. The last pictures are of it.

  And Stu, my apologies for hijacking your thread for my questions and education.

["Cadillac Kid" Greg Surfas 15364]

 But I guess the main question is, can I replace the original parallel style condenser with a newer serpentine design, or am I defeating the effectiveness of the system by doing it?
Richard, Yes the serpentine condenser is easier to flush out, but NO just replace the condenser with the replacement of the same ind. All the questions of performance were thought out by the factory so don't try and second guess them
Greg Surfas

[Cadman-iac]

  Thank you very much Greg, I appreciate your help on this. I wanted to be sure about it before I actually replaced the condenser, as I only want to do it once.
This discussion has been very enlightening.

Sincerely,

     Rick

[V63]

I have had 1955-56 with factory air and their condensers are all STEEL , serpentine and quite heavy?

all the credit to the original engineers to their efforts utilizing technology, materials,  manufacturing with associated costs, however all strictly LIMITED to that particular window of time.

Engineering could not And did not anticipate the influences We face today. We are dealing with expectations of Utilizing different refrigerants, oils and pressures🤦🏻‍♂️ Under different traffic conditions.

And Let's not forget the horrifically reduced octane fuels with alcohol blends the original engineers had zero anticipation. Moreover the Leaded fuel ban.

we have the OPTION of utilizing improved advancements of some 70 years.
Remember too...the cars are used differently today Under more extreme traffic conditions.

So a blanket obstinate to ever changing influences...To deny or accept reduced function ...makes no sense to me, past purely authenticity reasons.

["Cadillac Kid" Greg Surfas 15364]

You might "drop over" to the Modified Chapter forum.  We have no qualms about modifications or limits to the improvements in performance and creature comforts, and would welcome your input.
Greg Surfas
Director Modified Chapter CLS

[stushug]

   I don't want to hijack your thread Stu, but I have a question for Greg.

  I'd like to clarify this in my mind.  I'm not sure what design condenser Stu is installing, so I'm not clear on what you're getting at.
  Which design do you think is the better one, the serpentine design, or the parallel flow design?
I was under the impression that the serpentine design was better, (From some of your posts on other threads).
I'm currently working on my wife's car, and trying to get a serpentine design condenser that's not damaged before I remove it from the box. (Long story, see my thread about things changing yet remaining the same).
  Thanks for your clarification.

Rick

You don't want to hijack my thread, but you did!
No problem though, it opened up a lot of discussion and it's helping us all learn more about our cooling systems!

[stushug]

Greg,
I understand your argument for keeping the original condenser, and I agree with the argument you put forth. My problem is that I have done everything else that I can think of, yet I can't get anything below about 55 degrees out of my AC vents. I had my compressor rebuilt, purchased a new drier, expansion valve and a new POA valve calibrated for 134a. All from Classic Auto Air. I rebuilt the heater box, re-sealing the purge door. The heater core and evaporator core are in perfect shape. Short of swinging a chicken above my head, I'm not sure what else I can do.

["Cadillac Kid" Greg Surfas 15364]

Okay,
Let's get back to basics. At 55 degrees out the upper vents, what are the simultaneous conditions?
1. Outside temperature
2.Compressor discharge pressure
3. Compressor discharge temperature (of the discharge line)
4. suction pressure and temperature at the POA
With those numbers we can determine if the refrigeration system is working correctly.
Greg Surfas
Almost forgot, set the temperature dial to 65 degrees. Just looking at your current weather, if you are getting 55 degrees out the vents and it is 55 degrees outside, the ATC seem to be doing what you are asking.

[Cadman-iac]

I have had 1955-56 with factory air and their condensers are all STEEL , serpentine and quite heavy?

  You're right about this being steel. I had known that before after checking with a magnetic, but I haven't done anything with these, (I have 2 of them), for several years,  and when I was looking at one the other day it appeared to be a copper color under the black paint that had chipped or flaked away. I was in a rush and just assumed it was copper. But steel makes more sense considering the weight of these things. Thanks for pointing that out.

   Rick

[Cadman-iac]

  Stu,
Have you tried the hokey pokey yet?

Sorry, couldn't help myself,  lol !!

[stushug]

Okay,
Let's get back to basics. At 55 degrees out the upper vents, what are the simultaneous conditions?
1. Outside temperature
2.Compressor discharge pressure
3. Compressor discharge temperature (of the discharge line)
4. suction pressure and temperature at the POA
With those numbers we can determine if the refrigeration system is working correctly.
Greg Surfas
Almost forgot, set the temperature dial to 65 degrees. Just looking at your current weather, if you are getting 55 degrees out the vents and it is 55 degrees outside, the ATC seem to be doing what you are asking.

The days that I got those results, the ambient temps were around mid 70's.
I don't have any gauges, can you recommend a decent set so I can measure pressures? I'd also like the ability to recharge the system myself so I'm not dependent on the AC shop's schedule. I've read not to buy the small cans of 134a because they have leak sealer in them, so what's the best alternative for purchasing 134a?
Also, what is the best way to measure the discharge line and POA temps?

[Cadman-iac]

  Hey Stu,

The little cans of 134 don't all have the sealer in them.  I've noticed that the taller ones do, but the 14 or 12 ounce can does not. If you read the label, it should tell you if it's got any sealer in it.
I hate the fact that they even offer that crap, because people who don't understand these things install it and just cause themselves more problems.
As far as a gauge set goes, Harbor freight has a fairly decent set that's still affordable. They're not a professional quality set, but for occasional use, they work well enough.
I have two sets, one for R12, one for R134A. Not sure if it matters if you use the same set for both, but I didn't want to chance it myself.
Hope this explains your questions, since I hi-jacked your thread.
BTW, as you twirl your chicken, you have to do the hokey pokey and spin around 3 times, or something like that.

Rick

["Cadillac Kid" Greg Surfas 15364]

When using refrigeration gages BE EXTREMELY CAREFULL.  Wear goggles of some sort to protect your eyes and perhaps some god gloves until you get used to attaching and disconnecting the lines. Liquid refrigerant is extremely cold and contact with the skin or the eyes can result in instant frost bite. Not good.
Measuring temperatures in this day and age is easily done with an infrared thermometer, available just about anywhere that sells tools.
Greg Surfas