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Serpentine evaporator Pages: 12

ScotY on Wed November 14, 2007 5:42 PM User is offlineView users profile

Can anyone tell me what a serpentine evaporator is? A diagram, picture, etc. would be very helpful.

Tim or anyone from AMA,
What kind of evaporator do I have in my Suzuki kit?

bearing01 on Wed November 14, 2007 6:32 PM User is offline

It looks like an "s" shaped tube with fins. Like what you see on the back of your refrigerator.



Edited: Wed November 14, 2007 at 6:34 PM by bearing01

TRB on Wed November 14, 2007 9:15 PM User is offlineView users profile

64 pass tube & fin.

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ScotY on Wed November 14, 2007 9:45 PM User is offlineView users profile

Quote
Originally posted by: TRB
64 pass tube & fin.

Hi Tim,
Please pardon my ignorance, but what does that mean above? Is it like a parallel flow condenser in the way the tubes flow?

TRB on Wed November 14, 2007 9:49 PM User is offlineView users profile

No, similar to the image posted with 64 passes.

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HECAT on Thu November 15, 2007 8:45 AM User is offline

This article may help explain the different heat exchanger designs

http://www.hecat-inc.com/ACtion%20article%20Sep07.pdf

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iceman2555 on Thu November 15, 2007 8:45 AM User is offlineView users profile



Another view of a serp evap.

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson



Edited: Thu November 15, 2007 at 8:56 AM by iceman2555

NickD on Thu November 15, 2007 12:23 PM User is offline

In MVAC, is there such a thing as a parallel flow evaporator?

bohica2xo on Thu November 15, 2007 1:23 PM User is offline

Sure.

Parallel flow evaporator

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

TRB on Thu November 15, 2007 1:26 PM User is offlineView users profile

Plate and Fin would be similar but not exact.

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ScotY on Thu November 15, 2007 6:55 PM User is offlineView users profile

Quote
Originally posted by: TRB
No, similar to the image posted with 64 passes.

So my evaporator is a serpentine unit? The reason I asked was because I spoke to a local a/c tech and he mentioned that he had better luck sometimes with an OEM evap unit rather than an aftermarket part. He did say he has installed quite a few complete aftermarket systems in the past but did not mention AMA at all. He suggested I try and locate an OEM evap unit from a junkyard and give it a try. Is there any truth to his claims? Why or why not?

Thanks for all the help and info! I've really taken an interest in a/c stuff and want to keep learning.

Edited: Thu November 15, 2007 at 6:57 PM by ScotY

TRB on Thu November 15, 2007 7:56 PM User is offlineView users profile

Nope you have a tube and fin core as I mentioned before.

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ScotY on Thu November 15, 2007 8:17 PM User is offlineView users profile

Hi Tim,

So, in your opinion, would a serpentine evap work better? For now, I'm going on the assumption that an OEM evap is of serpentine construction. If you think it might work better, I will try to source one and give it a shot. I do understand that this is a small a/c unit so it might not blow as cold as something larger, like in my Dodge truck. But, I'm willing to experiment and try different things.

TRB on Thu November 15, 2007 8:22 PM User is offlineView users profile

We have those systems as originally sold cooling very well in the Arizona summer. If you only have a 20 degree temp as determined between you ambient listing and vent temp listing. You have some issue going on with the system. Hot air getting in, heater core issue or something else. Pressures indicate a cold evaporator core.

That just my opinion!

-------------------------

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

ScotY on Fri November 16, 2007 2:49 AM User is offlineView users profile

Quote
Originally posted by: TRB
We have those systems as originally sold cooling very well in the Arizona summer. If you only have a 20 degree temp as determined between you ambient listing and vent temp listing. You have some issue going on with the system. Hot air getting in, heater core issue or something else. Pressures indicate a cold evaporator core.

That just my opinion!

Hi Tim,

Okay, I'm not clear on what you're saying above. Do you mean the AMA kit or an OEM evap or an OEM complete a/c unit?

I know how hot it gets in Arizona so I figured whatever you guys sell should work really well. Of course, it's much more humid here so don't know if that has anything to do with it, but I would assume not? Since I am, by every definition of the word, an amateur, I'm here to get advice and learn from the guys who know.

Would there be any value in knowing the actual evap temperature? I could stick my thermometer directly into the fins and measure that also.

I value your opinion and that's why I asked about the serpentine OEM evaporator. Trying to confirm or deny what the tech guy told me. I know you guys don't sell OEM stuff, no one does for the Samurai anymore, so naturally didn't expect you to supply one. But if it might work better, I would be willing to try. And I will keep trying to figure out what might be wrong with my setup.

TRB on Fri November 16, 2007 12:23 PM User is offlineView users profile

Our kit cools fine in Arizona. I still think you should be looking at others areas besides the evap if you only have a 20 degree difference and a low side of 16 PSI. Core is cold at that point so why is the air only dropping 20 degrees?

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Contact: ACKits.com

iceman2555 on Fri November 16, 2007 5:53 PM User is offlineView users profile

When faced with a perceived cooling problem...it is best to know for sure that the system is properly charged. Reliance on pressures is not always a true indication of a completely recharged system....esp with the smaller recharge rates of some vehicles....and esp with aftermarket kits. With a known specified recharge rate...a suggestion would be to insure that the system is fully and totally charged. If lacking the proper equipment to measure total recharge rates....suggestion would be to have the system recovered, evac'd and recharged using the proper equipment. This will remove a major assumption in the diagnosis procedure....how much refrigerant is in the darn thing.

Evaluate pressures...but keep in mind they may vary from perceived OE specs. Evaluate temp drops....post info...lets us know. From the original post...seems pressures were the first concern...then temps came into play. Get it charged....evaluate both test parameters.

Test at idle...max cool..high blower...doors open....also at an elevated rpm....1200-1500 is sufficient....doors open and closed...measure temps/pressures and post results.

Be sure to include ambient temps...measure at the front of the vehicle....foot or so in front of the condenser.
The issue of the evap....three types are available...serp....plate and fin....and tube and fin. All have different heat absorption characteristics...which is better....that is probably a matter for another many post discussion. The industry follows the plate/fin and serp idea. Tube and fins are favored by the aftermarket kit suppliers....the ability to manufacture to custom specs is probably one reason. These have been used successfully for many years...heck for decades. They will work and should cool your vehicle.
Keep in mind the temp exchange requirements of your vehicle....fire wall....top...and other areas of insulation. Also engine cooling systems are sometimes different for non OE A/C cars. This can play a part in vent temps also. Engine cooling is most critical for proper cooling operations.

Back to the evap issue....statement to locate a OE evap may not be a salvation....it may not fit in the air box of your system. Measure twice to insure. But think the system you purchased can be properly configured to operate to your expectations.

Good luck...keep us posted. But first and foremost...get the thing charged correctly.




-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

ScotY on Sat November 17, 2007 12:28 AM User is offlineView users profile

Quote
Originally posted by: TRB
Our kit cools fine in Arizona. I still think you should be looking at others areas besides the evap if you only have a 20 degree difference and a low side of 16 PSI. Core is cold at that point so why is the air only dropping 20 degrees?

That is a good point and I will look at all possible sources of the perceived problem. I hope this is not out of line, but I like to discuss theory and stuff, too, not just looking for a direct answer/fix to the problem. That is how I learn, I have a need to understand everything...I can't help myself sometimes when I want to learn.

Anyway, I promise I will get some better data as soon as time permits. My schedule for working in the garage is limited. In the meantime, I wouldn't mind continuing this discussion and asking questions which I hope everyone doesn't mind answering/helping with?

ScotY on Sat November 17, 2007 12:39 AM User is offlineView users profile

Quote
Originally posted by: iceman2555
When faced with a perceived cooling problem...it is best to know for sure that the system is properly charged. Reliance on pressures is not always a true indication of a completely recharged system....esp with the smaller recharge rates of some vehicles....and esp with aftermarket kits. With a known specified recharge rate...a suggestion would be to insure that the system is fully and totally charged. If lacking the proper equipment to measure total recharge rates....suggestion would be to have the system recovered, evac'd and recharged using the proper equipment. This will remove a major assumption in the diagnosis procedure....how much refrigerant is in the darn thing.

Evaluate pressures...but keep in mind they may vary from perceived OE specs. Evaluate temp drops....post info...lets us know. From the original post...seems pressures were the first concern...then temps came into play. Get it charged....evaluate both test parameters.

Test at idle...max cool..high blower...doors open....also at an elevated rpm....1200-1500 is sufficient....doors open and closed...measure temps/pressures and post results.

Be sure to include ambient temps...measure at the front of the vehicle....foot or so in front of the condenser.

The issue of the evap....three types are available...serp....plate and fin....and tube and fin. All have different heat absorption characteristics...which is better....that is probably a matter for another many post discussion. The industry follows the plate/fin and serp idea. Tube and fins are favored by the aftermarket kit suppliers....the ability to manufacture to custom specs is probably one reason. These have been used successfully for many years...heck for decades. They will work and should cool your vehicle.

Keep in mind the temp exchange requirements of your vehicle....fire wall....top...and other areas of insulation. Also engine cooling systems are sometimes different for non OE A/C cars. This can play a part in vent temps also. Engine cooling is most critical for proper cooling operations.

Back to the evap issue....statement to locate a OE evap may not be a salvation....it may not fit in the air box of your system. Measure twice to insure. But think the system you purchased can be properly configured to operate to your expectations.

Good luck...keep us posted. But first and foremost...get the thing charged correctly.

Thanks, Iceman, for your detailed information! I understand what you are saying but, of course, a few questions. Hope you don't mind?

For charging, the instructions state a charge of 24 oz. However, I shortened some hoses because they were too long and hard to route. I cut off probably about a foot of so of hose in total. So, is there a formula for determining the amount of refrigerant required in a system? I could measure how much hose I cut off and calculate that volume if necessary. I'm assuming the shorter hoses will mean less refrigerant, but I don't know if the amount is significant or not?

I will post more detailed data as soon as I get a chance and will get all the data as you've listed. One question though on taking pressure readings...I noticed, in general, pressures increase as the engine bay gets hotter (heat soak). There's a slow upwards trend in high side pressure over time and it is fairly significant. How does one assess the pressures in this case when the numbers change quite a bit? The low side readings are a whole 'nother story. I can't figure out why they fluctuate so much.

ScotY on Sat November 17, 2007 3:20 AM User is offlineView users profile

Would it be possible (and accurate enough) to use a postal scale with 12 oz. cans of 134a to measure out the appropriate charge? Seems to me it should work if I disconnect the hose going to the can so it won't interfere with the scale reading?

Chick on Sat November 17, 2007 5:25 AM User is offlineView users profile

A postal scale will work, and it is sure better than nothing. But if you're going to be working on your car and "others" like family memembers, friends etc, I would suggest you get a refrigerant scale and a 30lb tank of R134a. Prices came down on tanks of refrigerant during the year, and although I haven't bought one in over a month, you can probably get 30lb around $75 to $80 bucks now (I will have to check, since I'm almost out too) There is no more accurate way, and check out the price of that quality scale. Can't beat it...

-------------------------
Chick
Email: Chick

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Freedoms just another word for nothing left to lose

iceman2555 on Sat November 17, 2007 10:20 AM User is offlineView users profile

Chick, why more scales are not used is a wonder. I have had a scale and heater blanket in my A/C tool bind for more years than I can count..or rather like to count. Sure comes in very handy when the R/R machine is tied up. For a mobile service van..these things are great. A small recovery only unit...a scale...blanket and wow....instant A/C service in a van.
It is amazing the number of operational shops (pros) today that lack the proper and legally required equipment to service automotive A/C systems. Often the cost of this equipment is stated as a reason...but the cost of a simple weight scale...a heater blanket is very small compared to the cost of doing a job over because the system was undercharged and the compressor failed. Add the benefit of knowing exactly how much refrigerant is in the system and being able to eliminate one aspect of the proper diagnostic procedure...go figure.
For about the cost of one compressor (new) one could have a scale and heater blanket and be assured that the proper amount of refrigerant is charged. With the decrease in recharge amounts, this ability to measure becomes much more important...on 14 oz recharge..how much does one take out of that second can??????
Thanks for the heads up!!!


-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

iceman2555 on Sat November 17, 2007 11:03 AM User is offlineView users profile

Scoty, when addressing the issue of removing hose material to facilitate installation....how much was removed? Unless a large quantity was removed, it is doubtful that the recharge amount sufficiently changed. There is a formula for recharge determinations...have to research the files for a post. However, unless the hose length was reduced by many feet...think I would stay with the suggested recharge amount.
Since the hoses were cut...assuming you did the cutting.....how were the hoses reattached to the fittings....wondering what clamping method was utilized. Hate to see a possible location for future leaks.
Regarding the escalation of high side pressures because of 'heat soaking'.....the engine cooling system is a most important part of proper A/C operations. Pressure readings should always be taken at normal operational temperatures. We often monitor these pressure readings over a period of time....let the engine idle for a bit and test pressures over an period of time. One of the best methods to test for proper engine/condenser cooling is to test temperature drop between the inlet and outlet of the condenser. Not sure what size or type condenser TRB is using with this kit...however, expect the temperature drop to be app. 20-25°. It is possible for it to be less...but make a test as soon as the engine reaches NOT. Retest at different times to determine if the temp drop changes...if the drop decreases...it is an indication that less heat is being extracted from the condenser...thus the elevated pressure readings. It is quite possible if the engine cooling system is not completely functional....one may see a complete inversion of the temp drop...the inlet becomes cooler than the outlet....this represents a serious problem. Hopefully this is not the case.
Also, it is not known if this vehicle was delivered without A/C. Some non OE A/C vehicles may lack sufficient engine cooling for the addition of an A/C system...in this case additional efforts may be necessary to insure correct cooling.
From the posted pressures and attempted recharge procedures (from your other post)...and unless something has changed drastically with the indicated pressures....the system seems to be functional...perhaps a bit of 'tweaking' here and there.


-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

ScotY on Mon November 19, 2007 3:30 AM User is offlineView users profile

Quote
Originally posted by: Chick
A postal scale will work, and it is sure better than nothing. But if you're going to be working on your car and "others" like family memembers, friends etc, I would suggest you get a refrigerant scale and a 30lb tank of R134a. Prices came down on tanks of refrigerant during the year, and although I haven't bought one in over a month, you can probably get 30lb around $75 to $80 bucks now (I will have to check, since I'm almost out too) There is no more accurate way, and check out the price of that quality scale. Can't beat it...

You know, when I first started installing the kit, I gave no thought to buying a 30 lb. tank thinking it's just way too much refrigerant and cost way too much. Now that I've bought a bunch of little cans at nearly $9 each, it sure sounds like I've been foolish with my money! Anyway, I don't want to fix anyone else's problems except my own so maybe I can just live with the little cans and let the auto parts store make their money.

ScotY on Mon November 19, 2007 3:56 AM User is offlineView users profile

Quote
Originally posted by: iceman2555
Scoty, when addressing the issue of removing hose material to facilitate installation....how much was removed? Unless a large quantity was removed, it is doubtful that the recharge amount sufficiently changed. There is a formula for recharge determinations...have to research the files for a post. However, unless the hose length was reduced by many feet...think I would stay with the suggested recharge amount.

Since the hoses were cut...assuming you did the cutting.....how were the hoses reattached to the fittings....wondering what clamping method was utilized. Hate to see a possible location for future leaks.

Regarding the escalation of high side pressures because of 'heat soaking'.....the engine cooling system is a most important part of proper A/C operations. Pressure readings should always be taken at normal operational temperatures. We often monitor these pressure readings over a period of time....let the engine idle for a bit and test pressures over an period of time. One of the best methods to test for proper engine/condenser cooling is to test temperature drop between the inlet and outlet of the condenser. Not sure what size or type condenser TRB is using with this kit...however, expect the temperature drop to be app. 20-25°. It is possible for it to be less...but make a test as soon as the engine reaches NOT. Retest at different times to determine if the temp drop changes...if the drop decreases...it is an indication that less heat is being extracted from the condenser...thus the elevated pressure readings. It is quite possible if the engine cooling system is not completely functional....one may see a complete inversion of the temp drop...the inlet becomes cooler than the outlet....this represents a serious problem. Hopefully this is not the case.

Also, it is not known if this vehicle was delivered without A/C. Some non OE A/C vehicles may lack sufficient engine cooling for the addition of an A/C system...in this case additional efforts may be necessary to insure correct cooling.

From the posted pressures and attempted recharge procedures (from your other post)...and unless something has changed drastically with the indicated pressures....the system seems to be functional...perhaps a bit of 'tweaking' here and there.

Hello Iceman,

Thanks for your info! I really get into your postings since they elaborate on theory and such and that helps me learn and understand.

I cut off maybe 1 foot of #10 hose and about 6" of #6 and #8 combined. I should have been more careful and measured just how much I cut off, but that's probably a fairly good estimate. So, a total of about 1.5 feet total. The volume of that hose relative to the rest of the system volume seems pretty small.

For connectors, I bought a crimper and fittings from AMA. The crimper was expensive but I thought maybe I would get more use out of it if I start modifying stuff in the future.

I will measure the condenser inlet and outlet temps next time, along with the other data that I need to collect. That's good to know re. engine cooling and stuff. I have been trying to find a fan clutch for a decent price with no luck so far. They are all over $100, most in the $130+ range! Wow, had no idea those things were so expensive. I just wish I could test it to determine if I should buy a new one. Alternatively, there is a company that makes a fan clutch "eliminator" which basically just replaces the stock fan with a metal fan, rigidly attached to the water pump. I might go that route but it worries me about a rigid connection there and possibly excessive fan speeds since the engine's redline is somewhere in the 6-7k range.

Suzuki dealers used to install OEM a/c units way back when. I actually had one that I bought brand new in the mid-80s. It also was a hard top version with the dealer installed OEM a/c. I seem to remember it working fairly well, but that was a long time ago so can't say for sure. Anyway, I sold that truck a long time ago but found this one recently, hence my little restoration project that will probably take me the rest of my life to complete! I found instructions for the OEM a/c installation and it's a lot more complex than the AMA kit since it interacts with the vehicle a lot more. I prefer simple. If you or anyone is interested in taking a look, I can send it, but it's a pretty big file.

Thanks, Scot

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