Relation between OP light and charge light?

[canadamatt]

Is there any relation between the oil pressure light and the charge light? My car died due to the battery not charging..first I thought it was simply a bad alternator. After I got it home I realized that the oil pressure light, and the charge light DO NOT come on when the key is at ACC. And the high beam light doesn't come on either when I put the high beams on. It all worked last week.

They're all separate bulbs, so thats ruled out. The gauge cluster plug is connected fine. The blinker indicator lights DO work. The rest of the gauge backlights DO work. The gauge cluster has extra grounds. All fuses have been replaced.

So can anyone think of a reason why I'd lose the OP, charge and high beams lights all at the same time? Doesn't make much sense to me, but then again, me and electricity have never really been best of friends...

thanks

Matt

[Beaner7102]

I know on some cars (not sure if it applies to 02's) that the globe in the alt light is integral to the charging circuit. If the globe is blown the Alt will not charge the battery, which may explain part of your problem. It is possible that the OP and HB globes happened to blow at the same time. Try replacing the 3 globes - even if they look OK. Beaner7102

[Mike Self]

As explained to me by an electrical engineer who knows this stuff better than I:

The "charge" light on an '02 dashboard is kinda unique in that both sides of the bulb are fed with a + voltage wire. One wire runs directly from the battery; the other from the alternator circuit. When the engine is off the bulb is illuminated by voltage from the battery; when the engine is running, the alternator provides the voltage, thus cancelling the battery's voltage and causing the light to go out. When the alternator isn't functioning properly, it isn't putting out as much voltage as the battery, so the lamp glows dimly, telling you something is wrong.

And when the bulb burns out, the circuit is broken and the alternator won't charge the battery.

Sounds like there's either a loose wire or a break in the circuit board that serves the three warning lights in your instrument cluster...

cheers

mike

[Paul7002]

(nt)

[canadamatt]

Yep, you guys are both correct about the charge circuit and how it works, but for the life of me I can't figure out the 'commonality' between the 3 lights that decided to go awol at the same time. I'm hoping there is a single power feed to all 3, but I would think the entire cluster would have one power feed, to power the warning lights, blinker indicator, high beams, backlight, etc.

Oh well, I guess its gonna be multimeter fun tonite

thanks

Matt

[Mike Self]

electrical stuff on the cluster wouldn't work) I'm guessing a fault in the circuit board--it's cracked across all three circuits. Not common on '02s, but pretty common on later BMWs (like E21s and E30s)

mike