GMC Repair: electrical, power door locks, buss bar

Question
99 olds lss 3.8- When I turn on the rear defroster it kills the engine, driver side power seat, power windows, power door locks, and the dome lights. After a cool down period all returns to normal. Are these all connected by a common ground buss bar that is bad, loose, corroded and where is it located? Voltage is good thru firewall fuses and power seat works without ign switch on so that should rule out voltage coming in. can you help me. this one is driving me crazy. thanks

Answer
Hi
The bus bar is the under hood fuse box.
I would check battery voltage AND alternator output with the rear defog on. It should stay constant (or close to it). MAke sure the engine RPM's are staying up.
Check the voltage at the Rear defog relay. It too should stay constant.
Check it on the B+ stud at the underhood fuse box. That is the buss bar in.
Thats where I would start.
I Hope this helps.
Good Luck
Pawl