I need to do some welding on the pipe that goes into the muffler. Muffler and pipe look good but you can twist the muffler a little bit. I want to put a bead of weld on it. Do I have to disconnect the battery in the car or the computers? I don't want to fry any electronics so I think I should at least disconnect the battery. Anything thing else I should do? The car is a 1993 300d and I will be using Lincoln wire feed welder if it makes a difference. Thanks in advance.

you need to disconnect the battery for sure.
Make sure your ground is very good and very close to the work. If possible I would try and isolate the exhaust by disconnecting it up the front and only have it on the rubber supports, still with the battery out.
I am not sure if the disconnection causes a problem with the radio. Others will comment soon.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

Agree with layback40.

Make sure you have all your hangers on before welding any exhaust so that the muffler will sit natural. We don't want any stress on those hangers later.

__________________
Codifex
1981 240D ChinaBlue (Got her running with a donor engine.)
1983 300DTurbo w/sunroof.
1984 300TD manual sunroof. (Electrical Gremlins)

My miller 175 has strict instructions to remove any metal from a vehicle before doing any welding to it... that said, I've welded the frame and bumper on my 97 suburban with no ill effects, but I grind the rust, paint, etc off the ground connection of my clamp, and keep the welding as close as possible to the clamp. that, and I didn't care much if I messed up the sub... I would be very leary of welding on a nice classic MB with things connected. I'd recommend removing the pipe, and welding it on the ground then putting it back in place.
my brother used my same welder on a 94 camaro and destroyed the 2000.00 cost to replace computer... YMMV...

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!