Richard,
Make sure the auxilliary water pump is not glitched and pulling more than ~1.3 amps. When it does it uses the PBCU as a fuse! Honest. Interesting MB "feature". This may explain the burned traces or it may not. ;)

Thanks for the advice. I just finished reading a thread over at the diesel forum in which several people stated that.

So, before I even look at the service manual, let me ask you these: 1) where is that aux. water pump located in my car? 2) How do I measure how much current it is drawing?

Thanks,

Richard

It's sort of under the monovalve between the two firewalls. Just pull the plug and test it or leave it unplugged as it is only useful at idle in cold weather.