BenzWorld Junior Member
Date registered: Mar 2018
Vehicle: 1988 300E M103
Location: Frederick Maryland USA
Mentioned: 0 Post(s)
Quoted: 5 Post(s)
Battery not charging - ignition switch related?
Before I begin, let me say that I have read several threads on non-charging problems, but I wanted to get some feedback on how best to diagnose this problem, given some pretty specific symptoms.
Background: I bought a cheap-ish '83 240D w/ 275K about a month ago - it had been sitting for over a year, but had a pretty good service history up through 2015. After replacing the battery and catching up on maintenance (oil change, front rotors & pads, tie rods) it was running fine for a couple of weeks until one morning when it barely cranked due to low battery voltage. Suspecting I might have just left an interior light on and drained the battery, I jumped it and drove 30+ miles but the alternator just wouldn't charging the battery. I drove it enough after replacing the battery to think that the alternator (which looked very old if not original) had probably just failed. I replaced the alternator with a 65 amp unit from AdvanceAuto, but it's still not charging.
As I said, I've read other related threads and have confirmed that the left-side dash lights (battery, brake, and pad wear warning) are all coming on when ignition is turned to position 2, so I'm pretty sure it's not the bad battery bulb problem described in some other threads. However, the pre-glow indicator light is working intermittently at best (more often not lighting now) even through I can hear the glow plug relay clicking off after ~15 seconds. The last time I got the pre-glow light to light up, it seemed to be sensitive to jiggling the ignition switch.
1) Is the non-lighting pre-glow light likely caused by a bad ignition switch?
2) Can a bad ignition switch interfere with battery charging?
3) If yes to (2), any way to diagnose a bad ignition switch (aside from replacing the switch)?
4) If no to (2), what the hell is going on? Thoughts on other things to check?