Trouble with "block style" txv for auto a/c use

[R717]

10129

Has anyone else experienced problems with style of TXV used in car A/C ?

I have encountered a number of examples that didn't seem to work as good as they should.

I suspected that there was no charge in the diaphragm (they have no bulb) so i cut a number of them open.

3 of them were brand new, 2 were used about 5 to 10 years old, one was used and 40 years old made by Ford in the 1970's.

Only the old Ford TXV had any refrigerant in the diaphragm, the others had not even a trace !!

The Ford one was also the only one that had a short piece of capillary tube used to charge the diaphragm, the others had nothing.

I wonder if the manufacturers are even bothering to attempt to charge these things ??

They only work in a limited way, they are basically a plain expansion valve dressed up as a TXV...............:confused:

[Grizzly]

An interesting question R717.
Maybe they are not thermostatic, but a form of regulating expansion valve?
With the pressures acting upon the underside of the diaphragm, controlling the orifice size.
A system does not need to control via TEV. (The Americans call them TXV)

So as you say maybe they just look like one as you say?
Good luck in your quest.
Grizzly

[monkey spanners]

Think they are thermostatic otherwise the systems would need an accumilator like the orifice tube models do.

Had problem with the block valve on my old Renault Master, took it out and blasted it out with cleaner and put back in, worked ok after! Van had a new condenser fitted by mechanics before problem arose.

Remember seeing a H pattern tev on milk tank years ago, didn't need a phial and cap tube as due to the design it could be in the actual vapour flow, seemed a very good design in principal but expect was too expensive to be competitive.

[R717]

Yes they are definately meant to be thermal expansion valves, they are advertised as such and also all reference made to them in any service manuals describes them as such and even describes their operation.

As i said only the old Ford one actually worked and if you chilled the valve by leaving it in a freezer you could actually measure some movement of the internal parts.

I thought the newer ones may be only acting as a Automatic expansion valve, but upon further investigation i found that no amount of force could move the diaphragm in the new valves.

On cutting them open i found the diaphragm was "fixed" in it's position by a spacer preventing it's movement so not even suction pressure could modulate the valve open or closed.

They really are just a plain expansion valve dressed up as a TXV.

There is expansion taking place across these valves, so some refrigeration effect takes place, but without thermostatic control these systems which are designed to have it work very poorly. I bet a lot of automotive A/C systems are condemned as being c#@p because of suspect valves as replacements or even original equipment.

I wonder if there is a bunch of counterfeit parts getting around out there ??

[Grizzly]

AH!
The old "But the salesman said" Ploy eh!
Thanks for the "Heads up!"
I will try and remember this for future referance.
Grizzly

[mikeref]

(R717) If these valves, and possibly other brands do not have the ability to "self regulate" then it could easily cause serious issues with compressor valves and oil. They are supposed to have a % control for obvious reasons. With a fluctuation head pressure under different driving conditions, i can't see how these valves could possibly pass quality inspection let alone work in with fixed or variable drive compressors.:(

[R717]

(R717) If these valves, and possibly other brands do not have the ability to "self regulate" then it could easily cause serious issues with compressor valves and oil. They are supposed to have a % control for obvious reasons. With a fluctuation head pressure under different driving conditions, i can't see how these valves could possibly pass quality inspection let alone work in with fixed or variable drive compressors.:(

I think they are causing serious issues with compressors and oil !!

I don't feel it is a quality control issue and a few dodgey valves got passed the inspection, i think they have been deliberately made this way.

If you are having trouble with a system using one of these, check the valve out in depth !!
And check new ones out too !!