My driver heated seat works occassionally. Like an idiot I replaced the $120 relay I got from the stealership and that wasn't the problem. I figure it is the lines that run the seat and one is cut and connects ever so often. I want to replace or fix the seat and add heat to the passaenger seat. What is recommended and an affordable project?

First off I'd put a meter on the leads to the seat to see if your getting power when need be.

Second to replace the coils and or add one you have to do a little upholstery. I hope your good with hog rings.

I agree with the meter approach.... stick a meter on the lines going up the back side of the seat and start wiggling things.

Adding a heater is a piece of cake. The seats are skinned with leather. Pull the seat out of the car(2 bolts). Starting with pulling out the retainer strips at the bottom just peel the skin back far enough to add the heater. The back heater is a little rough having to slip the heater between the skin and the cushion. Putting the retainer strips back in place can be a bit tedious, but no head scratching involved.
Not sure what circuit we tied into. I went to another project after the heater was in place on the seat.