Guys,

I been playing with these things and trying to figure out how to be very "safe" using them.
What I mean by safe is, how to NOT damage our W212 valve core , when and if pushing them down too much happened....can it actually happen ?

It all started here : https://mbworld.org/forums/e-class-w...lp-thanks.html

01. So I need to test, how far is the designed push rod travel of the coupler ? Are they all the same brand to brand and type to type ?
02. How far can a valve core be pushed down safely ? There are many different valve core design.

I am sure SAE or similar body will govern the basic design of this HVAC fitting and tool, because this is a refrigerant leaker and US EPA always pay attention to this "emission".
The latest r1234YF refrigerant, is well covered by SAE and I am surprised to the level of detail on how, why and the insane US$40,000+ penalty per event, by simply using an r134a evaporator on a r1234yf system.

Anyway here are my findings.

How I measure the travel of the coupler push rod. I use what I have ( r134a male fitting from Aliexpress for training purpose) , as I can't do it on the car system. The test is valid, that's the good news.





The W212 valve core.
























If the valve core has a spring at the push stem like JRA one, one need to be extra careful. Its maximum allowable travel is not as long as it seems.





Below test is using the Aliexpress r134a test port which uses the JRA valve core.


See, the risk if a coupler push rod can go too deep...... damage can occur to the valve core.
I wonder what is the travel depth/distance of Yellow Jacket LP coupler ? Iyello Jacket HP looks safe and decently big opening at 2.07mm. The China HP one is more aggressive at 3.03mm.

The China LP one, I wonder why so small an opening, 2mm would be nice. Now wonder my vacuuming process using it is so slow and extra slow when using the MasterCool LP.




POTENTIAL VALVE CORE DAMAGE FROM A COUPLER : As explained by a very professional car/commercial HVAC tech, my favorite car HVAC guy on youtube. 2nd paragraph.






.




Links :
MasterCool Kit .
China coupler, this is one of the best one I can find : https://www.aliexpress.com/item/4001...21ef1802mwSlMz

If Yellow Jacket, HP : .
LP : I bought the Yellow Jacket HP one last year specific for micron gauge reading only when I go to a proper HVAC workshop, never knew I would eventually want to DIY the HVAC works this year.
I will be ordering the LP coupler from Yellow Jacket.




Now I realized why the MasterCool LP fixed depth coupler is on purpose having the LP side so small an opening at only 0.43mm super small and the HP side is also small opening at 1.15mm.
The LP side is made on purpose very small opening to mimic an orifice, this is to make liquid r134a captured when returned to the LP side or suction side by using a running car compressor
suction , it will gas off as vapor. Compressor can not compress liquid refrigerant, it is a gas compressor and not a water/liquid pump. If liquid compressing, a liquid hammer damage it will get.
If you see the video below, you will understand what I mean :

So aside from slowly opening the LP valve at the tube while it has to be on top at highest, that on-purpose small opening LP coupler will gas-off the liquid r134a even better. Wow... not it make sense such a small opening compared to its HP coupler.
Taking only gas form r134a is like as though as one is using a 30 LBS r134a bottle up right and not inverted, so that only vapor is being given out by the bottle.


We would like to think that every product for r134a follow SAE standard, but seems not.
The maximum travel distance of the coupler push rod will also depend on how is the r134a port in the car is designed. The locking ball groove distance to the top will dictate.


Top to locking ball groove end
MB LP & HP ......................: 9.63 mm & 10.06 mm
Mastercool LP only.............: 10.07 mm
China unknown LP & HP......: 8.60 mm & 9.10 mm



Comparing MasterCool LP port and the practice ports from AliExpress, by visual.



========


Parking Depth of the valve core U shoulder to top, matters too, as they are not the same if different type of valve core is used.

The W212




Parking Depth of the valve core U shoulder to top :
China practice port, HP 11.77mm , valve core is JRA type.
China practice port, LP 12.00 mm , valve core is JRA type
MasterCool, LP ony 8.87mm , standard tire size valve core



Locking ball position at the coupler also dictate its seating depth at the port. Sorry, I can't measure them, you can see for youself.

Yellow Jacket HP coupler, its locking ball position compared to the China unknown brand, it is not the same.




MasterCool vs China unknown. MasterCool stuff most are from China too.





Why I am so concern on the maximum depth of the coupler push rod ?
01. The spinning knob of the adjustable coupler which control the depth of the push rod is big, so your fingers torque is multiplied a great deal and easy to over tightened or push too deep to the valve core.

02. At 100 psi static charge of the car r134a at 30C temperature, I can not feel the push rod resistance to the motion of the valve core opening, as there is 100 psi pressure pushing the valve core stem.
I can feel the valve core opening if there is no pressure or pressure only by my mouth blowing air, when I was practicing using the Aliexpress LP and HP r134a port.



So keep an eagle eye on the gauge while spinning the push-depth adjustment knob slowly.
When pressure rise at the gauge occurs, maximum do 270 degrees more turn or 180 degrees to be safe.

Hope this information will be useful when you want to buy the coupler.