Change auto AC's default fan speed?

I'd say live with it.

If the outside temp is COLDER but the sun is out, the temperature in the AC unit may be high enough to make it think it needs the blower on high speed. As soon as the temperature drops in the AC vents, it will adjust automatically. This is all perfectly normal.

 

Not sure, but I think OP is referring to the set interior temp, ie: the number set as target temp on the Heat/Vent LCD display.

 

I've worked on the old Harrison mechanical "automatic temperature control systems" used in GM cars and Rolls Royce cars in the 1969's and 1970's.

On those systems, both the compressor and the heater were always "on" with temperature controlled by an ail valve called a "diverter door."

It would surprise me that Toyota would use the same system on the "energy frugal" Prius system.

The basic laws of thermodynamics and physics do not normally change.

The Toyota system uses an "orifice tube," NOT a thermostatic expansion valve or the newer "intelligent" expansion valve in very expensive major building systems. If the compressor runs and moves refrigerant, something has to happen to slow the expansion of refrigerant or move more air through the evaporator.

 

FWIW, my ScanGauge reports a range of wattages when the AC's on. Minimum is 150 I think, and it sometimes runs up to around 400. Also, when the AC button is off but Mode is set to Heat/Defog, I'll sometimes see AC wattage showing some values. It's typically lower and intermittent, comparing to times when I do turn on AC with it's button.

 

Mechanical refrigeration systems are also "dehumidifiers." That's why they may be activated when the controls are set in the Heat/Defog mode.

 

That is warped logic. Most of the time that cooling is occurring, the fan is NOT at high speed.
And when the system is first started the 150 degree air going through is not likely to let anything freeze.

 

My fan rarely begins on high speed unless I set the temp low on a warm day or high on a cool day. Today it actually started at the 2nd bar when I got done grocery shopping. The outside temp was 76 on the display and the auto was set for 72, it was probably 80 inside the car.

 

I was trying to find out if by chance he was thinking the Outside Temp reading was the interior. The interior temp can only be displayed with OBD device.

For him to say that the setpoint and interior temp were only 1 degree different but the fan speed was high does not add up for auto control. If the setpoint and outside temp were only 1 degree different the interior temp could be much higher, resulting in the high fan speed.