I changed the ignition switch on my '93 240 after the shame of hot-wiring it finally got to me. I was in a rush and it had gotten dark, so I started to drive without plugging any of the stuff on the back of the instrument panel in, thinking I'd just take care of it in the morning. On the freeway I gradually lost power (radio, lights, and eventually fuel), the same way you'd lose power from losing/shorting the alternator and draining the battery.

I had a no crank situation, with 12V even on the battery. A jump brought me back to life and I drove home (5 miles) just fine. I'm really hoping that this had something to do with the instrument panel being unplugged - any theories/wisdom?

all that said... a 5 mile drive should not drain a battery to the point where the car won't start. Even with headlights on.

I think you might do well to budget for a battery pretty soon...

I lost my charging system coming home from a road trip ('84 240)... Bought two new batteries in the nearest small town. First battery got me about 300 miles with lights off, but stereo and heater on. Stopped for gas and it still started and got me another 10 miles with lights on. Second battery got me home, about 15 miles with lights, heater fan, stereo on, and the car started fine the next morning.



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-Matt I ♥ my ♂

You do need the instrument cluster installed for it to charge.

Good luck!

On my 1990 245 if you don't have the white angled edge connecter, over by the speedometer connected, the alternator won't charge the battery.

Also on my 1990 there is a wire for the tachometer, which I don't have. It is white and red connecting it to anything but a tachometer will be catastrophic, I taped it up first thing when I removed the instrument cluster for the first time. Post back with the outcome.

Fred

Ok it all makes sense now. You need the instrument cluster to charge the battery (how else would the little red warning 'battery' light work?)

I recall trying to figure out where the R/W Tach wire connected for a few hours the first time I pulled the cluster many moons ago. It has since been labeled at "plugs into nothing".

Thanks for the sanity check. I wasn't looking forward to considering any alternate(or) theories.