Short Circuit
 

I have an '85 190E that just started exhibiting strange behavior. After I start it and turn on electrical things(radio, headlights, reverse lights) the headlights dim for a second and the radio blanks out. I shift into reverse and the same thing happens. If I start to drive and then hit the brakes, it loses electricity again. It usually straightens out after a few miles. I haven't checked the fuses yet. Are all those things on the same fuse? I don't lose total power, it's almost like a brown-out...

Jim

Check the tension on your belt?

my boss had same problem on his 85 500 sel, ended up being the alternator.

...or the battery is going south and can't maintain an adequate charge.

Keep us posted,

Haasman

...or an alternator "overcharging" problem has occurred, which could cause the same symptoms (as it had on mine).

Get an OVM and check the voltage across the battery terminals with the engine on (accessories off) and engine off.

Should read 12V when engine is off and ~ 14.4V when engine is running. Anything much lower than this indicates a charging problem. Mine was an overcharging problem, and my voltmeter read 17.5V!!! :eek:

If your belt tension is okay, you may just need a new regulator. Your car is an early enough model year that you can replace just that portion of the alternator (mine is internal, so I had to swap the alternator :( ).

Typically, it may be that the brushes are worn...

Brand new battery... so that shouldn't be it. I'll check the belt tension and voltage tonight.

I'm driving the 300D today and my wife has the 190E. The 300D won't shut off. I have that narrowed down to a vacuum issue.

I've seen ignition switches cause similar strange behavior. Just a guess though.