Re: Unknown switch
Posted: Tue Nov 10, 2009 2:11 pm
As far as I can tell from the diagrams, yes, it uses a transistor and a bypass relay for the highest level here is the circuit;

Power transistor for Lo to Medium - G3-04 controlled by Pin 2D, then relay G3-05 comes in to bypass the transistor for Highest speed - switched by Pin 3P.
The transistor is located in the same / similar place as the resistors I believe;

The A/C unit also has a feed from the controlled side of the motor Pin 2E, so it could sense what speed / voltage is being applied, also it should be able to sense that the main control relay G3-07 has operated. Exactly what it does with the data is another matter - there isn't an internal circuit diagram to give that info.
In all there are three separate diagrams for the blower controls, the two above and a third simpler system for the rear A/C.
P.S Edit
- Just read the latest release of the Fact sheet and yes it discusses the two different systems and tells you that the transistor is a 2SD1525 device.

Power transistor for Lo to Medium - G3-04 controlled by Pin 2D, then relay G3-05 comes in to bypass the transistor for Highest speed - switched by Pin 3P.
The transistor is located in the same / similar place as the resistors I believe;

The A/C unit also has a feed from the controlled side of the motor Pin 2E, so it could sense what speed / voltage is being applied, also it should be able to sense that the main control relay G3-07 has operated. Exactly what it does with the data is another matter - there isn't an internal circuit diagram to give that info.
In all there are three separate diagrams for the blower controls, the two above and a third simpler system for the rear A/C.
P.S Edit
- Just read the latest release of the Fact sheet and yes it discusses the two different systems and tells you that the transistor is a 2SD1525 device.