Effects of adjusting AC expansion valve - PeachParts Mercedes-Benz Forum

RichC · #1 07-10-2011, 02:29 AM

Anyone ever adjusted the expansion valve in their AC system ?

What effects did it have ?

Experience only please, no opinions, or repeating what a book, or someone else has said.

Thank you

compress ignite · #2 07-10-2011, 03:18 AM

Far,Far,Far Outside the "Box" on this one.

'Mos Complicated: Trigonometric/Algebraic/VooDoo extensions of Thermometric Engineering involved.

Unsolicited Analogy:
I decide,for whatever Reason(?) I'm unhappy with my S.S. 15.5 X 19 Yamaha Propeller...
I take a Set of AutoBody tools to it for Remediation.
If I'm not happy with the results,how do I get it back to the O.E.Configuration?
[How DO I Measure the BALANCE of it once it's ADJUSTED ?]
(I am reassured, because no matter how Badly I Screw it up,there are two Marine machine shops that can "Fix" it on the river here in Town.)
BUT it may cost 1/3 to 1/2 the price of a nice USED S.S. prop.

What ARE you (or think you're trying to) trying to accomplish with the "Adjustments" ?

Good Luck (On this Forum [Planet?] ) with locating anyone ADVENTUROUS
enough to have done It.

Call ACKITS ,If anyone has tried it, They'll have knowledge.

(From a note of Personal Interest...How Youse Gonna keep anybody on this forum from putting in their 1/2 cent of Opinions ?)

vstech · #3 07-10-2011, 07:23 AM

I did not know they were adjustable.

I adjust txv's all the time on refrigeration and high efficiency systems.

they do not control temperature of the coil directly. they control the amount of superheat allowed to reach the compressor within their design parameters (flow capabilities) of the coil/compressor/blower heat transfer capabilities of the system

tell me what you are trying to accomplish, and where adjustments can be made, and I'll assist/talk you out of it...

leathermang · #4 07-10-2011, 09:13 AM

They are adjustable .... in the MB FSM for AC..
and Jabaj007 ( has done it...and written in the archives about it ). His name may not be spelled correctly....
Many feel that it takes special measuring equipment to do it... unless one does not mind putting the system together and completely taking it apart in a trial and error methodology....

Did you search the archives first ?.... since you wanted only first hand experience .

leathermang · #5 07-10-2011, 09:22 AM

Quote:

Originally Posted by compress ignite

......From a note of Personal Interest...How Youse Gonna keep anybody on this forum from putting in their 1/2 cent of Opinions ?)

X 20, LOL
Even asking it that way sorta violates the bigger premise of an open forum....better to just ask... and ignore whatever you want to which is not ' first hand ' experience in this case....

RichC · #6 07-10-2011, 10:59 AM

There is a spring in the expansion valve that holds a pin in a passageway.

That is one, of the two ways, that the expansion valve regulates flow.

Much like a needle jet in a carberator.

Springs can get weak with use.

And the flow of refrigerant could be changed by the worn spring.

1980sd · #7 07-10-2011, 11:48 AM

Check out the big Four Seasons catalog at NAPA. They have a zillion different TXV's in there with different superheat values listed. Seems like they were 4, 5, and 8 I think.

My car just uses a 3/8" flared input and a 1/2" flared output on the TXV. And you can easily stick any TXV with a 1/2" flare on the evaporator.

They may have an externally adjustable TXV, you'd just have to make sure it has similar parameters to the original.

But, yea, it's my understanding that it just "throttles" the liqiud so it boils into enough gas to make the the cheezy little foreign evaporator work.

I say find an externally adjustable valve and go for it.

leathermang · #8 07-10-2011, 02:08 PM

Remember that ours is a " Block " valve.... has the Txvalve and the throttle suctioning valve in one rectangular metal case... so if you put just a Txvalve substituted for the block valve some method of regulating the down temp side will be needed...
and no mention yet of the effect of the atmospheric connection and its effects...

RichC · #9 07-10-2011, 02:12 PM

123 and 126 bodies come with adjustable valves.

leathermang · #10 07-10-2011, 02:15 PM

Quote:

Originally Posted by RichC

123 and 126 bodies come with adjustable valves.

I have a 123 with the type one AC...
Are you referring to the Txvalve being adjustable... or another adjustable valve in addition to that ?

Anyone remember the correct name for our friend out West that has messed with adjusting these things ?

1980sd · #11 07-10-2011, 03:05 PM

116 valve:

If you look through the catalogs there are MANY equilizing type TXV's that look exactly like this one, and are direct bolt ons. It looks like a very generic design that can have lots of internal differences. They have many different fixed superheat values with no apparent external differences.

Theoretically, you could install a TXV for a Freightliner that would BOLT RIGHT UP but probably wouldn't work well, and you wouldn't know... You would just have to go on the assumption that you have the right part!

Not sure what type you have on your car.

RichC · #12 07-10-2011, 06:30 PM

123 and 126 bodies expansion valves can be adjusted by turning
the whole cap that is opposite the thermostatic control.

Or on some, a small plug inside the cap that has two holes drilled
to fit an adjustment tool.

leathermang · #13 07-10-2011, 07:19 PM

Quote:

Originally Posted by RichC

123 and 126 bodies expansion valves can be adjusted by turning
the whole cap that is opposite the thermostatic control.

Or on some, a small plug inside the cap that has two holes drilled
to fit an adjustment tool.

That is true... now, turning it which way does what ?
What are the signs it needs to be turned ?
What happens if it is turned too far ?