So whoever owned my Formula before me ran the power windows up (without the door panel and weather stripping on) and the glass got caught on the screws that hold the outer belt line window weatherstrip on. Looks like it stressed/cracked a 2” section of the inner door. Window functions fine. I was looking to put a couple tack welds (MiG flux core) to keep it from getting worse. If I weld this I’ll disconnect the battery for sure. But what about the ECU? Or is it no different from getting an exhaust system welded? Thoughts?

 

I would disconnect the battery, just as good standard practice.
Don't forget to "stop drill" the crack before welding.

 

You should be fine as long as you don't hit the wires with the welder. Make sure the welder ground is on the door very near the weld area. I would disconnect the wires and move them out of the way. I would also tack weld all along the crack like you would with a butt weld on a patch panel. Only a couple of tacks might encourage it to crack elsewhere along the existing crack with vibration over time.

 

Excellent. Very good tips. I'll do those. Thanks!