Re: Electrical through a cold air return
Please ignore the reply from hannahmd(who is a spammer) and contact your local building inspector or a home inspector. My home inspector was none too pleased to find wiring and a gas lline in my air return, and I am actually removing it soon which leaves me with the issue of plugging the holes. and making them airtight.
I highly doubt a licensed electrician would run the line thgrough the return, so consider that if you want to do it.
It's this old house, not this built after your dad was born house.