nickel_work87

That is a good question. I have no clue. I just wish that it was more specific.

RLXXI

True but our trucks do not utilize an orifice valve, we have thermostatic expansion valves (txv) I wish we still had the orifice because it was easy to change out, cost about $5.00 and as you said, different sizes to fine tune a system.


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gwpfan

The only way to truly properly diagnose a AC system one needs
Refrigerant Type
After at least 10 minutes of operation
Hi Side Pressure
Outdoor Temperature
Liquid Line temperature
Low side pressure
Return air humidity
Return air temperature
Suction Line Temperature
Supply air temperature
Supply air humidity

From the above we can tell the amount of btu's being transferred and also how well the system is operating. This will also allow one to calculate superheat and subcool - among the most important tell tale factors of how a system is operating. Sure pressures and ambient temperatures will typically get you in the ball park, but a real diagnosis includes values to be able to calculate superheat (how much heat is coming back to the compressor - ideally 10-20 deg F, lower is not better) and subcool (how much liquid refrigerant is available to be used across the metering device - TXV/Piston - ideally 8-12 deg F). Note both ideal numbers are based on near design conditions, typically 95 deg outdoor and ~75 deg indoor. The numbers tweak slightly as those conditions change, but one should almost always have at least 10 deg F superheat and 5 deg F subcool.

I would be extremely cautious on the potentiometer fix. If you do this then find the specs for the temperature and set for no less than 32 deg F (for a 2010 approx 99,000 ohms based on chart in post #23).

If there's a problem and this is set too low you will either burn up or slug your compressor and either failure requires a new compressor and a bunch of labor and quite possibly a lot more.

The reason I'll go as low as 32 deg F is that we know the coil has to be continuously be below 32 deg F to freeze water, once water starts to freeze though it blocks airflow and the process of the refrigerant absorbing heat is hindered. If it becomes hindered enough the liquid refrigerant will not boil to a vapor and then you'll get liquid back to your compressor and that liquid will damage the pistons/valves of the compressor as it is not designed to pump liquid, only vapor. If one finds 32 doesn't cut it then I might go down to 30 deg F ~110,500 ohms for a 2010, but again be cautious.

The outdoor damper is a great idea, especially in humid climates as humidity removal takes up a lot of BTU's. I would simply put this on a switch, else use your recirc as it should do the same thing. Only issue is if one disables permanently sometimes one will get an odor from the moisture being left on the evap, where if you dry it out before turning the vehicle off you'll be less likely to get the AC startup odor.

digitaltrucker

Can the txv be adjusted by any means?

papa tiger

Believe it has a temperature control bulb connected to it so it is sealed hermetically. It is unlikely it would fail but it could be blocked by ice in the refrigerant or some particle not allowing enough to flow. Again here is where a tech is needed to make the call to replace one. Constant cycle while low side still remains low in pressure may be indicative of a blocked txv. or pump. Keeping the clutch engaged all the time is not a safe fix.

RLXXI

No.


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digitaltrucker

Any updates from those that have done this?

Bigdog364

I now have 172500 miles. A/C still has the 10k ohm potentiometer installed. Cooling great. As the outside temps get lower, more chance of it freezing up. When the vent temp drops to around 30°, I turn off the a/c selector off. Just let the fan run till the vent temp rises. I may put a on/off switch on it. As done by rymax101.

digitaltrucker

Would not the blend door, when adjusting the temp control, help?

Bigdog364

Good idea. I will try it. Does the heated air come in before or after the condensor? I dont know the airflow pattern inside the plenum box.?