Thermal Expansion Valve - sanity check

[jeepsj]

Neighbor came over with his New Holland T5040 tractor. Sympton is inconsistent AC function. Hooked up the gauges and when the system kicks on we are getting high side approaching 350psi while the low pressure drops to 20 and the system kicks off.

Condenser and evap are both clean. He takes immaculate care of the thing. Plenty of airflow over the condenser and wetting the condenser doesn't change anything.

My thought is bad or failing expansion valve. Am I on the right track?

Also does anyone have the R134 capacity of the system? It is a 2015.

Thanks

[tbirdtbird]

Agree 20/350 not good. Interesting that wetting condenser = no change, since it would seem to be a condenser issue. Probably kicking off on high pressure. Which type of TXV? Block style? Are you sure it is a TXV, and not an orifice tube?
You said symptom is inconsistent AC function. That implies that it works normally sometimes. What are the pressures then?
Tractors are FAMOUS for building up dust and dirt accumulation on any finned coil. Knew a sheetrocker whose AC on his Dodge van crapped out. The fins of the evap were totally clogged with white sheetrock dust.

Feel by hand. The pipe in and out of the evap should be about equally cold. Filter dryer should be hot.
Using infared thermometer, measure temp diff of condenser top and bottom. There s/b a 30° temp difference. If not the coil fins are clogged.
Testing s/b done with engine at 1800 RPM and max fan/max cool. Doors open.

Do the coils just look good? Regardless of testing, I would flush both coils vigorously with at least air pressure. Clean the condenser with a coil cleaner or basically a heavy duty detergent such as simple green. Avoid ionic coil cleaners, they actually slowly eat away at the fins. Looks shiny tho!

Are fans electric? if so are they all actually working? Working at full capacity? I have seen electric fans get tired and weak.
Has any work been done to the system? Has anyone added 134, or added sealer, or a can of 134 with sealer in it? (which you never want to do!)

Feel along the lengths of the hoses and pipes. If you come to any cold areas, then you have an internal blockage, and the blockage is acting as an expansion device.

If the high side can go to 350, then the fault is not at the compressor.

Finding system charge could be a challenge. Got access to a New Holland shop manual, or google it, or ask dealer, or call New Holland.
You are not ready for any 134 at this point, tho

[jeepsj]

The TXV is a block style. Confirmed it is a TXV and not an OT system. Fan is mechanical with no clutch. Evap snd condenser are both clean. When I say inconsistent I mean that it cycles and blows cold then warm then cold then warm.

[tbirdtbird]

That would mean that there are different gauge readings when warm vs cold.
Any chance you can post both sets of readings under the conditions mentioned,
ie, testing s/b done with engine at 1800 RPM and max fan/max cool. Doors open.
Also post the results of the hands on "feel" tests.
Without good diagnosis you could easily head in the wrong direction.

[tbirdtbird]

For the block valve, get a can of computer dust-off spray. Invert can, and spray the liquid on the sensing disc. The high side should drop about 50 psi and recover when the frost melts.
If it only drops 10 psi, then the disc is faulty.

[Tim]

I'd start with a proper evacuation and charge procedure. Know your baseline so to speak.

[JohnHere]

Asking around the agrarian/equestrian area in which I live, the consensus is that the refrigerant spec for your neighbor's tractor is 3.5 pounds of R-134a (with a Sanden compressor).

You might also check with these folks who specialize in agricultural-vehicle A/C to verify: AP Air, Humboldt, IA.

Have you looked for an under-hood decal for the A/C specs? If it has one, the decal would take precedence.

[tbirdtbird]

I am unable to find the 134 capacity of your model.
The T 5050 takes 3.5 pounds, not sure if that helps.
The owner must have the manual if he bought it new

oops John beat me to it

[bohica2xo]

Any service history on the equipment?

It is cycling on the HPCO.

Could be a blockage, kinked or damaged line, too much oil in the system.

A TXV that is not opening will generally show a low side that drops to very low pressures, or even vacuum. The refrigerant should stack up in the R/D and condenser at a somewhat elevated pressure.

I agree with Tim, recover it and weigh what you take out. At that point you can determine the next step.

[ice-n-tropics]

Clogged evaporator fins and air in the refrigeration system would give somewhat same results
hotrodac