I'm putting back an AC system in my 71 dart . I'll be putting in a sanden type compressor and a parallel flow condenser. Is the stock evaporator good enough or the newer ones much better? small tubes more fins? Thanks Jim
ac evaporator
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67Dart273
Well-Known Member
If this were me, I'd hook it up and try it.
You might want to figure out how to monitor the system 'for a bit' going down the road, that is, suction temperature and operating pressures.
Either that or you need a mechanic / shop you can bribe that has "big fans" to run it in place
You know what is meant by (suction) superheat and how to measure it?
"Generally" here's what you are looking at.
Heavy heat load, that is, hot, cab hasn't cooled, or system capacity is a little low, will lean towards higher suction pressure and higher superheat
Light heat load, or cab has cooled, or larger system which can easily overcome, leans towards lower suction pressure and lower superheat.
More refrigerant, drops the superheat
Heavy heat load, "smallish" condenser runs high side pressures up, leans towards higher superheat
Lighter heat load or oversize condenser runs high side pressures down. Leans towards lower superheat
Compressor leaning towards low capacity as to the rest of system leans towards lower high side, higher low side.
Mismatched metering device, IE expansion valve, WITHIN LIMITS can regulate itself, but there is of course a limit. "Too big" means flooding the evap, higher suction pressure and lower superheat
Too small means lower suction pressure and higher superheat.
You have to use your head. No pun intended LOL. Keep in mind "what the cab" is doing for heat load and "what the condenser" is receiving for airflow. If you are in a shop with a too-small fan, you will never be able to simulate conditions you want
What does this all mean? For one thing, it means you do NOT want to come up with an overcharged system which will flood the compressor suction with liquid under "adverse" conditions such as
low cab temp on a cool day, also made worse going down the highway on that cool day producing low high side pressure.
THE NUMBAH WHAON worst thing you can do is produce a situation that will allow liquid back into the compressor
You might want to figure out how to monitor the system 'for a bit' going down the road, that is, suction temperature and operating pressures.
Either that or you need a mechanic / shop you can bribe that has "big fans" to run it in place
You know what is meant by (suction) superheat and how to measure it?
"Generally" here's what you are looking at.
Heavy heat load, that is, hot, cab hasn't cooled, or system capacity is a little low, will lean towards higher suction pressure and higher superheat
Light heat load, or cab has cooled, or larger system which can easily overcome, leans towards lower suction pressure and lower superheat.
More refrigerant, drops the superheat
Heavy heat load, "smallish" condenser runs high side pressures up, leans towards higher superheat
Lighter heat load or oversize condenser runs high side pressures down. Leans towards lower superheat
Compressor leaning towards low capacity as to the rest of system leans towards lower high side, higher low side.
Mismatched metering device, IE expansion valve, WITHIN LIMITS can regulate itself, but there is of course a limit. "Too big" means flooding the evap, higher suction pressure and lower superheat
Too small means lower suction pressure and higher superheat.
You have to use your head. No pun intended LOL. Keep in mind "what the cab" is doing for heat load and "what the condenser" is receiving for airflow. If you are in a shop with a too-small fan, you will never be able to simulate conditions you want
What does this all mean? For one thing, it means you do NOT want to come up with an overcharged system which will flood the compressor suction with liquid under "adverse" conditions such as
low cab temp on a cool day, also made worse going down the highway on that cool day producing low high side pressure.
THE NUMBAH WHAON worst thing you can do is produce a situation that will allow liquid back into the compressor
67Dart273
Well-Known Member
That's pretty damn funny. How do you propose to find that out LOL?
thanks for the reply 273 I went to ebay and found they make parallel and serpentine evaporators just like condensers . A parallel condenser is supposed to be 30% cooler( don't know I just read it) does that hold true for the evaporators? Am I wasting my time looking for a parallel evap. are they more efficient than serpentine evap for all I know there may be nothing wrong with mine except dirty. Jim
67Dart273
Well-Known Member
Frankly I'm not sure. Any vehicle I've worked on was pretty much stock, so you "assume" the designers matched them OK.
I had worked in residential / light commercial HVAC for a number of years. We occasionally hung a coil on an old furnace, with a somewhat unknown blower, or once in awhile replaced a condensing unit using an existing old evap, but of course those are fairly well marked.
With the stuff I worked on, if you DID get in trouble a bit, you could usually "jiggle" the system some by adjusting the charge, changing the TXV or orifice up or down, and going from there.
As I said before, I fully plan on throwing a Sanden and condenser off a later Dodge pu onto one of the ebay evap units. In other words it seems to me worth the gamble to "find out."
I had worked in residential / light commercial HVAC for a number of years. We occasionally hung a coil on an old furnace, with a somewhat unknown blower, or once in awhile replaced a condensing unit using an existing old evap, but of course those are fairly well marked.
With the stuff I worked on, if you DID get in trouble a bit, you could usually "jiggle" the system some by adjusting the charge, changing the TXV or orifice up or down, and going from there.
As I said before, I fully plan on throwing a Sanden and condenser off a later Dodge pu onto one of the ebay evap units. In other words it seems to me worth the gamble to "find out."
I don't know enough about AC but it seems to most of the heat transfer happens at the condenser . I can only find comparisons between serpentine and parallel condensers not evaps I'll just keep looking . Maybe I'll take your advice Clean it up and put it back. Thanks for the info Jim
67Dart273
Well-Known Member
No, it happens "at both ends." As I tried to indicate, the entire system must be "matched" up to a point.
Compressor capacity is probably least important so long as it's not too large in relation to evap and especially condenser.
In the "refer" and other commercial world, there is actually systems that are variable capacity, and in older large refer installations in grocery stores, sometimes one system will have more than two evaps in different coolers with independent controls.
"These are not ideal" for performance and efficiency.
Just use your head and "think" about what is going on. An A/C is a "heat pump" that is, it is absorbing heat at one end and rejecting heat at the other. Also, the compressor and mechanics of operation ADDS more heat that also must be removed.
In the case of most residential systems, where the compressor motor is inside the compressor shell, that motor heat and friction is also added, and must be rejected---removed.
If you cannot easily change the size of the major components, the things that you somewhat CAN do is
change the airflow (blower) through the evap. Less airflow means less heat absorbed, and less system capacity is needed
change the airflow through the condenser if possible. Less air means higher head pressure, and less system capacity "to a point."
change the charge (refrigerant) This is mostly to protect the compressor after decent operating temps / pressures are reached
change the TXV or orifice up or down. This is probably the single most useful tweek you have.
If you are inventive enough, you could even change the speed (crank pulley) of the compressor.
Compressor capacity is probably least important so long as it's not too large in relation to evap and especially condenser.
In the "refer" and other commercial world, there is actually systems that are variable capacity, and in older large refer installations in grocery stores, sometimes one system will have more than two evaps in different coolers with independent controls.
"These are not ideal" for performance and efficiency.
Just use your head and "think" about what is going on. An A/C is a "heat pump" that is, it is absorbing heat at one end and rejecting heat at the other. Also, the compressor and mechanics of operation ADDS more heat that also must be removed.
In the case of most residential systems, where the compressor motor is inside the compressor shell, that motor heat and friction is also added, and must be rejected---removed.
If you cannot easily change the size of the major components, the things that you somewhat CAN do is
change the airflow (blower) through the evap. Less airflow means less heat absorbed, and less system capacity is needed
change the airflow through the condenser if possible. Less air means higher head pressure, and less system capacity "to a point."
change the charge (refrigerant) This is mostly to protect the compressor after decent operating temps / pressures are reached
change the TXV or orifice up or down. This is probably the single most useful tweek you have.
If you are inventive enough, you could even change the speed (crank pulley) of the compressor.
jbc426
Well-Known Member
The condensors for R134 refrigerant are available online. I was told R134 needs a parallel flow condenser. I measured my radiator opening on both my Mopars and ordered one that would best fill the opening. They ended up being larger than a stock one, but fit nicely.
Thanks jbc how did it cool and did you use a stock evaporator? jim
Pete in NH
Well-Known Member
Back when these cars were new A/C was a $400 option on a $3300 car, so it was a fair percentage of the car price. For this Chrysler did dive you something for your money and the components used were nicely overdesigned. The RV series compressors were some of the most rugged ever put in a car and the evaporators and condensers were real copper and brass of a decent thickness. Unlike new cars where evaporator problems are fairly common the old stuff almost never failed.
I would have no problem using an original evaporator if it were in good physical condition. If you compare it to the newer aluminum/plastic stuff made today you'll see what I mean about the quality level of the older stuff. I'd flush out the original evaporator and use it.
On the condenser, Yes, R-134A is less efficient that the old R-12 and a parallel flow condenser helps transfer heat better to make up for this. And, you want to move as much air through the condenser as you can so a good fan and shroud really help.
I would have no problem using an original evaporator if it were in good physical condition. If you compare it to the newer aluminum/plastic stuff made today you'll see what I mean about the quality level of the older stuff. I'd flush out the original evaporator and use it.
On the condenser, Yes, R-134A is less efficient that the old R-12 and a parallel flow condenser helps transfer heat better to make up for this. And, you want to move as much air through the condenser as you can so a good fan and shroud really help.
67Dart273
Well-Known Member
This is a simple concept that many don't understand. R-12 is also more efficient than R22, used for decades in AC units.
I don't remember anymore but I believe AMMONIA trumps them all. YEAH!!! Let's do THAT!!! Let's use AMMONIA in our car systems LMAO
rednesss
Well-Known Member
I have a 68 Barracuda with factory ac, and I am running a Sanden pump and a new condenser, reusing the old evaporator and TX valve, and am running R12. I threw a little less than 3 lbs into it just this weekend, I believe the manual calls for 2 lbs 10-14 ozs. That is of course using the boat anchor of a RV2 pump. I wasn't sure if I should compensate considering the Sanden pump. Not knowing if the RV2 pump vs. Sanden would change the capacity needs up or down. Or whether the new condenser that I have is bigger or smaller than the original factory. Anyways, it's been too damn cold to really get a good read on the system. It was like 60 degrees yesterday, barley. My low side was a bit low in my opinion at 22, and my high side was only 135. Compressor cycles on and off. I just need it to warm up into the 80's to see if my pressures are in a good range.
67Dart273
Well-Known Member
Since you are using R12 read the service manuals. The operating / test conditions they outline in there should be 'by the book' both literally and figureatively.
I would guess there just might be a slight difference in capacity. I'm not trying to be smart, that's what thermometers and pressure gauges are for.
The only time a set amount of refrigerant is relevant is when you have a known, "as built" system.
You cannot properly test a system with no effective load "in the box." With a 60* ambient I'd say that is gonna be tough
I would guess there just might be a slight difference in capacity. I'm not trying to be smart, that's what thermometers and pressure gauges are for.
The only time a set amount of refrigerant is relevant is when you have a known, "as built" system.
You cannot properly test a system with no effective load "in the box." With a 60* ambient I'd say that is gonna be tough
rednesss
Well-Known Member
Yeah, that's why I'm hoping for a nice sunny day and some temps in the high 80's to drag my gauges back out and see if the charge is anywhere near where it should be. Hard to get it right when it ain't hot out unless you have a stock system with a known capacity and weigh it in.
mderoy340
Well-Known Member
Run the old evaporator its better than the new junk of today. You need a good fan and shroud to dump the heat. I've never changed the expansion valve since the R12 ones work great on every conversion I've done. When using 134 Fill system with 75% of R12 sticker capacity and then add if needed after reading pressures.
2 Darts
A-body Addicted
LMAO X 2. "Lez do a flame test on dat thang fer leaks."
IIRC, oxidizing ammonia produces an explosion (see West, Texas), and oxidizing R-12 produces phosgene (see Battle of Ypres, Belgium [WW I]).
rednesss
Well-Known Member
Propane makes a good refrigerant too.
67Dart273
Well-Known Member
LOTS of things are "on the table" "sort of." Most people just don't realize that when the Freon family of refrigerants was invented and developed, engineers thought they had the world by the tale
A refrigerant should:
Operate well under the temperatures and pressures of the system. Hell, CO2 is a refrigerant, but the operating pressures and temp is extreme. Actually it IS used in some ?cascade? ultra low temp stuff
Mix with oil and not destroy seals, and internal parts
It would be handy if it wasn't explosive or flammable
It would be VERY handy if it wasn't toxic or poisonous.
"Before my time" they used methyl chloride and sulfur dioxide, both very nasty indeed. One of them, under adverse conditions, would remove copper from the tubing and deposit it on the cylinder walls of the compressor.........not really what you want.
jbc426
Well-Known Member
I used the Vintage Air Gen V and a shoty Sanden compressor. I mounted the compressor under the Alternator, as I have it in a 1970 Shaker-hooded, 440-6, 'Cuda, and don't like the look of the top of the engine mount a lot of guys use.
It cools O.K., but I think the "shorty-sized" Sanden is too small for the system to be of maximum efficiency.
Pete in NH
Well-Known Member
The RV type compressor used on /6's was about 9.5 cu. in. displacement and the RV-2 type used on V8's was about 10.5. I would look up the Sanden type you want to use and match up the displacements. Also, watch the Sanden type you use some are speced for R-12 only and others are R-134A depending on the seal materials used.
On refrigerants, wait until R-1234yf really starts moving in and R-134A starts getting expensive. That will really boost sales of the Hydrocarbon mixes or Propane/Butane.
On refrigerants, wait until R-1234yf really starts moving in and R-134A starts getting expensive. That will really boost sales of the Hydrocarbon mixes or Propane/Butane.
BillGrissom
Well-Known Member
No real problem if the AC compressor is over-sized since it is cycled on & off as needed. I put a Sanden "shorty" H13 (13 being displacement in cc?) in my 1985 M-B and cools fine. I understand there is an even smaller H12, but most brackets are made for the H15 length Sanden. If your evaporator becomes the "limiting factory", it should still work great, since the factory AC in my 69 Dart was icy cold in FL (using R-12).
Re refrigerants, I run Duracool (hydrocarbon) in all my cars now. I changed the 1996 & 2002 ones to it recently when both compressors seized. No sense going back to R-134A since it is to be banned (already in France). HC is used in home refrigerators in Europe. Read for yourself and try to weigh the rants from AC professionals. I use PAO 68 oil, which seems best for any refrigerant.
I recently searched HO-1234yf and read that M-B did simulated crash tests which found a puncture burns violently (from oil spray), which converted the refrigerant to deadly HF gas. It etched the windshield and is very bad for your corneas and skin. They refused to use it and are currently fighting France over denying import of their cars w/ R-134A. Might be over-blown since Freon changes to deadly phosgene gas in a fire, but we used it for decades. I fear not the 12 oz of Duracool in my cars. The cans feel almost empty.
Re refrigerants, I run Duracool (hydrocarbon) in all my cars now. I changed the 1996 & 2002 ones to it recently when both compressors seized. No sense going back to R-134A since it is to be banned (already in France). HC is used in home refrigerators in Europe. Read for yourself and try to weigh the rants from AC professionals. I use PAO 68 oil, which seems best for any refrigerant.
I recently searched HO-1234yf and read that M-B did simulated crash tests which found a puncture burns violently (from oil spray), which converted the refrigerant to deadly HF gas. It etched the windshield and is very bad for your corneas and skin. They refused to use it and are currently fighting France over denying import of their cars w/ R-134A. Might be over-blown since Freon changes to deadly phosgene gas in a fire, but we used it for decades. I fear not the 12 oz of Duracool in my cars. The cans feel almost empty.
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