Brake Lights On! Now whats this tank I found?
 

Help! Brake lights are suddenly out on my '76 240D. Checked the fuse, checked the bulbs, checked the switch at the pedal, and lost the switch wire where it goes into a big bundle under the dash. Does it all run through a relay somewhere over near the emergency brake? Eliminated the wipers and turn sig. relays, but can't figure the rest. BTW the foot switch for the wipers suddenly makes the wipers actuate

Possibly the ground connection in the trunk.

More likely a poor fuse connection due to thin corrosion on the fuse.

Try substituting a different fuse of the same color in the fuse box.

Ken300D

I agree with Ken300d, sounds like a fuse problem. From the factory they used aluminum fuses which tend to corrode up and cause random problems. There are now copper fuse upgrades which work perfectly for this, but I still use die-electric grease to be positive of no more problems from that area.

Here's what it turned out to be. That piece is inside the reflector assembly and is a big circuit board with what looks like cast aluminum leads. the next post has a closeup of the hairline crack breaking the circuit.

While hunting this down I did find a strange flat black plastic tank behind the spare tire with a bunch of hoses attached. Any ideas?

That took out both tailights' brake lights?! I'd like to wire up a third brake light to my benz eventually, maybe one of those 12 LED lights. :)

Actually one side was the bulb. Must have been running on the one, and assumed they both went at once. Wondering if there was more juice flowing through the good bulb, burning it out quicker?

While hunting this down I did find a strange flat black plastic tank behind the spare tire with a bunch of hoses attached. Any ideas?

Possibly your Vacuum Storage tank. Stores Vacuum pressure to actuate the door and trunk locks.