I found these lines in the Apollo 14 Lunar Surface Journal:
116:07:37 Mitchell: Houston, the current reading is 8.
116:07:42 McCandless: Understand 8 amperes before pressing the (shorting) switch.
116:07:49 Mitchell: That's affirmative.
RealVideo Clip (3 min 44 sec)
116:07:50 McCandless: Roger.
[Comm Break. The shorting switch helps keep the RTG from overheating before current is applied to the experiment packages. In essence, the shorting switch provides a resistance equivalent to the full array. Ed's report of the ampere reading is the fourth item in the 2+00 paragraph in his checklist.]
The ALSEP RTG had 1480 W thermal power and only 70 W electrical power at 16 V DC. I doubt that shorting the RTG would prevent an overheating of the RTG itself.
So I applied the basics of electric sources, their internal resistance and the maximum power transfer matching to the ALSEP and its RTG.
To use the maximal electric power of the RTG, the load resistance should be matched (equal) to the internal resistance of the RTG. Without any load, the RTG voltage is two times the voltage at a matched load. So the open circuit voltage was 32 V.
AS14-67-9366 (OF300) ( 150k or 978k ) 117:17:41 Down-Sun picture of the RTG with the Central Station in the background. The fins on the RTG provide radiative cooling. Note the relatively large amount of dust that has been kicked on to the RTG. The smaller object in the background is the LRRR. The mortar pack is at the right edge.
When ALSEP was installed on the Moon, the RTG was connected to the central station and the several experiments were connected to the central.
Here is my interpretation of the shorting switch:
When the RTG was connected to the central station only but without any experiment, the output voltage of the RTG would have been too high and might damage the central station. To prevent a damage, the RTG was shorted at first and the shorting switch was released after all experiments were connected and nominal load to the RTG was connected.
Any other thoughts of the shorting switch and its purpose?