Posted by John (188.8.131.52) on July 16, 2004 at 22:10:49:
In Reply to: Battery switch; Can/should it be done while motor is running? posted by Paul on 13:10:42 07/13/04:
My understanding is that some battey switches are more reliable than others in maintaining a contact when switching from one to the other (or to both if you have a 4 position switch).
Also, dirt and corrosion from age can make the contacts less reliable and could break that contact even though the switch design is good. You could easily use an electrical tester (with the batteries disconected please)to check continuity when you are switching.
As you have heard, it is considered bad to switch off with the engine running as the allternator diodes can be damaged although I have done it a couple of times accidently without a problem. The fact that your engine died quickly may have saved you from damage. Diesels will keep running and may be more susceptible to damaging the alternator.