The 737-200 is not my strong suit, but in the absence of any other answers here goes.
1. Yes there should be. Power for the gen oil temp gauge is from 28V DC bus 1/2.
2. Either the APU or the battery via the inverter.
3. The GB's cannot be closed automatically. They can only be closed by you putting the gen's on at the overhead panel.
4. Similar to Q3, APU GB can only be closed manually at the overhead panel.
You should have been given the three golden rules of 737 electrics:
1. There is no paralleling of AC power.
2. The source of AC power being switched on takes priority and disconnects the existing source.
3. A source of AC power does not enter the system automatically (when it reaches proper voltage & freq). It must be manually switched on.
It is this last one that applies to your two last questions.
S & L
PS The last rule does not apply to NG's
PPS Edited to add the PS.
Last edited by CaptainSandL; 23rd Aug 2005 at 17:44.