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Old 08-02-2019, 03:31 PM   #1
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E-Z clip #6,8,10 or 12?

So I've decided to gnaw on the bullet and repair the rear AC myself.
Mostly I have the tools figured out. Found a source for a 30lb can of 134a. (might be enough)
What sizes of fittings and hoses should I use and where? I plan to put high and low charge/service ports at the compressor

got a charge/temperature chart to follow
http://realpropertyalpha.com/p/2018/...t-for-134a.jpg

I understand starting at compressor the r134a is a high pressure gas, That goes through the condenser and becomes a liquid, That goes through the TxV at the evaporator and becomes a vapor again all the way back to the compressor.

I have 3 freon lines for each system. Will I need 3 different sizes of hose and fittings? I havent seen any markings of the old stuff.
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Old 08-02-2019, 08:20 PM   #2
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yeah the most common format is #10 Discharge line from Compressor to condensor.. #8 liquid line from condenser to evaporator, and #12 suction from Evaporator to Compressor .. ive seen system done with 6,8,10. but only the snaller units.. your hose should be stamped with the size in either english or metric and we casn convert to AN number from there..

-Christiopher
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Old 08-02-2019, 08:21 PM   #3
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the other thing is if your systen has been opened up for awhile, you need to replace the receiver/ dryer and also evacuate the system with a vacuum pump... if you skip the vacuum then you have air and moisture in the lines which are non-condensables and will affect cooling performance..
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Old 08-02-2019, 08:45 PM   #4
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I do plan to vacuum it down and already have the new filter dryer. Thank You for all the advice and help you give on this forum.

You mention in another post that your system puts out 40F air. My front system is at 65F with engine RPM over 1k. Condenser fans come on but cut off . Evaporator feels cool but not cold. Pressure switch on condenser or low on freon?
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Old 08-03-2019, 07:06 AM   #5
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some systems only run the condenser when the pressure goes up.. others run it anytime the compresser is on..



if you dont have a gauge, theres a couple things you can do..



1. is the liquid line Hot? (line coming from condenser toward evaporator{condenser outlet}).. if the fans arent running when they should, the output of the condenser will be pretty hot fairly quick... esp if its to the point of the inside unit losing cooling..

its normal for the condenser inlet line to be hot.. that one should be on a hot day..



2. if the freon is low the system may be cycling on low pressure.. if theres a sight glass on the current dryer or inside the grille if its a Trans/AIR. you should see it at least 1/2 to 3/4 full of bubbling liquid when the system is turned on.. if you see it going nearly empty then the system is low on freon..



I tend not to charge them till that sight glass is 100% clear.. I dinf they run ab it cooler if im charged to the point of 3/4 to maybe cycling clear and bubbling as the TxV does its job..



in an over-charged system you'll see that sight glass always full. and not even bubbling when the compressor kicks in and out..



-Christopher
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Old 08-03-2019, 01:40 PM   #6
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With the Comfort Bus in the shop getting the trans swapped, I have to wait until its out to see about getting the condenser fans to run while the system is switched on. Might simply need to set up a relay with a on/off switch on the dash panel.I may be over simplifying it but a cooler output from condenser would equal a colder evaporator. When I checked the condenser fans they all appeared to move plenty of air. I have a Robinair gauge set bookmarked and I can use thermal temp device to get input and output temps of condenser and evaporator. I do have sight glasses to check as well. Thank you again. I'll update later when I have more.
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Old 08-04-2019, 06:39 AM   #7
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I was looking over the wiring diagram last night while having a drink in a Hotel bar, and for my Trans/AIR system on the red bus, the condenser relay is tied to the Low pressure switch.. on that system, the Low PSI switch is tied to the Low-side Suction Pressure.. os if the freon gets low, the effect will be the compressor and Condenser fans cycling constantly on/off/on/off. on that system the condenser fans also cycle with interior temp thermostat..



condensers typically have a heck Surge pull on the relay and electrical system.. (perhaps why I had to replace the condenser relay on that bus)..


ProAir made the controller for my DEV bus.. and their recommended wiring diagram is to use a Binary High / Low pressure switch on the High side of the system.. idea being that if the standing pressure (system off freon pressure).. is too low, it wont cool anyway so dont even try).. that switch also acts as a High pressure switch.. (kicks out at 385 I think on high)..



their mentality is different, in a bus you have nearly zero Ram air through a condenser, so anytime your A/C is on the condenser fans will need to run a lot. so they have the fans on anytime you set the Mode to A/C. and just cycle the compressor based on on other factors..

each one of thoise evaporators has a freeze sensor in it, if the coil temp drops into the danger zone where you are going to freeze it up, that sensor trips out..



they have you make one large loop with the High / Low PSI switch, and the freeze sensor on any evaporators.. so any one of those goes open and you kill the compressor but leave the condenser on..



this is how mine is wired now.. originally I wired it to cycle the condenser as well wit ha secondary relay for the condenser.. ProAir engineer scolded me and said that those motors and relay are designed for continuous use, but that excessive cycling will shorten the life of both..



Driving during the day down here in Florida the compressor doesnt cycle much during the day, but at night it kicks in and out alot against the freeze sensors.. (this is not a flaw.. it means im making those coils cold enough to do the job)..



its nice not having my lights surge down and up each time like it did previously..



I dont recommend a manual switch simply because its all too easy to forget it.. ands thats H*LL on a compressor to run it up against its high pressure switch. or worse yet if your system's High PSI switch is no good, you break things quickly..



testing High PSI switches is a tough proposition.. you certainly dont want to charge the system with 400 PSI of Nitrogen as you'll likely destroy the evaporator pretty handily...



-Christopher
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Old 08-04-2019, 12:29 PM   #8
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With the Comfort Bus in the shop getting the trans swapped, I have to wait until its out to see about getting the condenser fans to run while the system is switched on. Might simply need to set up a relay with a on/off switch on the dash panel.I may be over simplifying it but a cooler output from condenser would equal a colder evaporator. When I checked the condenser fans they all appeared to move plenty of air. I have a Robinair gauge set bookmarked and I can use thermal temp device to get input and output temps of condenser and evaporator. I do have sight glasses to check as well. Thank you again. I'll update later when I have more.
Unless you system is grossly undercharged, the temperature drop in the condenser will mostly influence the high side pressure. Evaporator outlet temperature is predominantly controlled by the thermostatic expansion valve (TXV).

It is a good idea to measure pressure AND temperature as only both tell you the full story.

Let's just recap some Physics to understand what is going on inside of an A/C system.

If we start with a system that has only gas in it (which is NOT what we have in an A/C), the pressure is a function of the volume of gas in the system and the temperature. We can use the ideal gas law to calculate the volume of gas if temperature and pressure are known. An example would be a SCUBA tank. If the tank holds 80 cuft of air at 3000 PSI then at 1500 PSI we have 40 cuft of air left. The influence of temperature is relatively insignificant in the range the human body can function but it is noticeable when you enter cooler water with tanks that have been sitting in the sun before. Therefore, divers can use a submersible pressure gauge (SPG) to verify how much breathing gas is left in their tank(s).

This is NOT going to work in a two phase system where we have liquid and vapor. If you measure the pressure of a liquid propane tank for example, you will see that the pressure is now only a function of temperature. The amount of liquid propane in the tank does NOT change the pressure as long as there is liquid and vapor in the system.

We have the same situation in an A/C system. The refrigerant exists in a liquid and vapor phase. The reason for the two phases is that we are using the latent heat of the phase transition to do the work. Anytime we vaporize a liquid, heat is removed from the surroundings. This is how our body cools itself through evaporation of sweat. If that vapor condenses again, the exact same amount of energy gets released to the surroundings. That energy is what fuels thunderstorms and hurricanes.

In an A/C, the liquid refrigerant gets evaporated by removing heat from the cabin air flowing past the fins of the evaporator. To make this a closed cycle system we need to turn the refrigerant back into a liquid but the problem is that we are now below ambient temperature and the heat has no incentive to flow back from our refrigerant to the surroundings. That's where the compressor comes in. We raise the pressure and subsequently the temperature of the refrigerant vapor to a point where we can use another heat exchanger, the condenser, to release the latent heat of condensation to the surroundings. At the outlet of the condenser we now have a liquid again and the heat we sucked out of the cabin has been released to the surroundings plus the energy put into the compressor. The liquid refrigerant coming out of the condenser gets collected in a receiver/drier and then flows back towards the evaporator. A fixed orifice or the variable orifice of a TXV just before the evaporator core provides the separation between the low and high pressure side. Without this restriction, the compressor could not raise pressure and temperature to make the condensing with ambient air work and the temperature of the cabin air would not be sufficient to evaporate the liquid.

Here is how a typical refrigeration process looks in a Pressure-Volume diagram.

Pretty cool invention, huh? (pun intended).

The key is the liquid-vapor-liquid transition and common automotive refrigerants are chosen to facilitate this at the design temperatures and pressures and also provide other desirable features like being non flammable and non toxic for example.
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Old 08-04-2019, 01:43 PM   #9
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Whoe, That is slot of information. Thank you both for the knowledge. It will take me a little bit to absorb it but rest assured your efforts are not wasted.
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Old 08-04-2019, 05:31 PM   #10
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Whoe, That is slot of information. Thank you both for the knowledge. It will take me a little bit to absorb it but rest assured your efforts are not wasted.
I can guarantee that your efforts to understand the physics will pay off. Once you understand the principles that make a refrigeration system work, any problems will be much easier to troubleshoot.

There is another key phenomenon that I should have elaborated on. The boiling point/temperature of a liquid, which is also the condensation temperature of its vapor, depends on pressure.

We all know that water boils at 100 degrees Celsius or 212 degrees Fahrenheit. But that is only true at sea level pressure. When we evacuate a refrigeration system with a vacuum pump, we are lowering the pressure so much that the water boils off at ambient temperature. That is more practical than heating the entire system to 100 C at 1 atmosphere.

In a pressure canner we are doing the opposite; increasing the pressure to prevent the water from boiling at 212 F so we can raise the temperature to a point where bacteria/spores like Clostridium botulinum will be killed in low acidity foods.

In an A/C system, the refrigerant will condense at a higher temperature than where it evaporated because of the higher pressure in the condenser. That allows us to have the evaporator colder than ambient and the condenser hotter than ambient to get the heat flowing in the direction we want.

BTW: the Eaton EZ-Clips you mentioned in the title of this thread require a special, reduced diameter hose. I prefer this hose since it routes easier that the regular OD hose but DIY crimp-on fittings for reduced OD hose are rarer and more expensive than for regular OD hose. Interestingly, most of the factory made hose assemblies use reduced OD hose with crimp-on fittings. Bottom line is to measure both ID and OD of a hose before ordering a fitting.
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Old 08-04-2019, 06:16 PM   #11
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I use good year Galaxy Hose for my Clip style fittings.. I havent had any issues with it yet..



I use BurgaClip fittings .. they are a little harder to find, however i have a supplier who sells me all of them I want.. (ProAir LLC in elkhart indiana).. If you want to go this route, get me a BOM and I can either order them for you or we can see if Jeff will make an order for you.. they get pretty busy up there but he seems to make time for me..
-Christopher
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Old 08-04-2019, 06:49 PM   #12
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Sitting here being blown away by all this. It's going to be a couple of months before I can start ordering supplies for the A/C. I will gladly take you up on that offer after the labor for the trans swap is paid.
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Old 08-05-2019, 12:44 AM   #13
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I am so glad you started this thread! Also very glad of the responses.
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Old 08-05-2019, 06:35 AM   #14
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what trans swap did you do? 545 to 643?



I just drove from Columbus Ohio to Key west. my first REAL road trip out of flat-country through some hills with my 643 since the swap. and wow what. difference to actually not just run against the Rev limiter all the time! and have decent power..
-Christopher
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Old 08-05-2019, 07:20 AM   #15
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Yes. Got one from LKQ. Arrived in a steel crate. I already had the flex plate, shorter flywheel bolts and new rear main seal. Might as well replace it since they are digging into it. The shop that is doing the swap was amazed at how much the renewed transmission was. They were thinking about getting a couple and storing them until a customer needs it. I'm headed over there in a bit to drop off the Transynd and take a few pictures.
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Old 08-05-2019, 07:30 AM   #16
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I just drove from Columbus Ohio to Key west. my first REAL road trip out of flat-country through some hills with my 643 since the swap. and wow what. difference to actually not just run against the Rev limiter all the time! and have decent power..
-Christopher
I am looking forward to that. Giving the engine more fuel and actually feeling it pull. Have you had any problems with hard shifting?

Bus Grease Monkey on YouTube just had 12/22.5's installed. Says he loves it. It's too bad he only works on Detroit 2 strokes and associated buses.
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Old 08-05-2019, 07:44 AM   #17
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Yes. Got one from LKQ. Arrived in a steel crate. I already had the flex plate, shorter flywheel bolts and new rear main seal. Might as well replace it since they are digging into it. The shop that is doing the swap was amazed at how much the renewed transmission was. They were thinking about getting a couple and storing them until a customer needs it. I'm headed over there in a bit to drop off the Transynd and take a few pictures.
Although I have a 3126 Cat I think I'm going to get one of the LKQ 643's while the gettins good.
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Old 08-05-2019, 08:20 AM   #18
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I use good year Galaxy Hose for my Clip style fittings.. I havent had any issues with it yet..



I use BurgaClip fittings .. they are a little harder to find, however i have a supplier who sells me all of them I want.. (ProAir LLC in elkhart indiana).. If you want to go this route, get me a BOM and I can either order them for you or we can see if Jeff will make an order for you.. they get pretty busy up there but he seems to make time for me..
-Christopher
Of course, Eaton wants to sell their hose but any other reduced diameter hose should work too with these fittings.

BurgaClip fittings also require reduced diameter hose. See page 352 here.

I wish they would do away with the regular OD hose altogether. It's a legacy design from the R-12 days. Once the PET barrier was introduced in hoses to reduce the permeation of the much smaller R-134a molecules, the old style rubber wall thickness became pointless.
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Old 08-05-2019, 08:22 AM   #19
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Yes. Got one from LKQ. Arrived in a steel crate. I already had the flex plate, shorter flywheel bolts and new rear main seal. Might as well replace it since they are digging into it. The shop that is doing the swap was amazed at how much the renewed transmission was. They were thinking about getting a couple and storing them until a customer needs it. I'm headed over there in a bit to drop off the Transynd and take a few pictures.
Interesting!

We need another thread on this transmission swap.
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Old 08-05-2019, 08:27 AM   #20
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Interesting!

We need another thread on this transmission swap.
YES we do!
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