starting confusion

[redvetracr]

I have a 94 f-350 dually crewcab IDI not quite 80K miles. Yesterday about 32* out I tried to start the truck...click click click, I found a loose and corroded terminal on the batt closest to the solenoid, so I cleaned all 4 terminals, disconnected the batt with the green eye and charged the batt with the loose terminals...10 hours later the green eye is still dark and the acid is not bubbling, even checked the specific gravity with a hi-tech tester where you put a drop on a glass and look through to see the reading (1 cell dead and all the rest in the 1130-1180 range).Plugged in the block heater for about 1-1/2 hrs this morning and guess what?? With the good (green eye) batt still disconected the truck started right up.....Is this the oddest thing or what?? Oh yes I also forgot to mention BOTH batteries are the ORIGINALS from 1994.....What am I missing here?? (besides it`s time for two new batteries).......redvetracr

[aceohearts]

Even a single dead cell in a battery will drain down a system like crazy. I had one dead cell in the 3 battery system in my semi, and it sucked the volts down enough to interfere with the ECM. Replace both batteries at the same time, you thank yourself later. [img]/ubbthreads/images/graemlins/smile.gif[/img]

[yaric008]

I'd say replace the batteries and go. Powering up those glow plugs and then having to crank that big starter takes a bit of power. So one battery might not be able to do it well. Plugging it in probably gave that one battery a head start.