I inherited my 99 Grand Cherokee from my dad when he died, and he had switched in a set of heated, power leather seats. The wire harness for the power seats were right there and they work fine. He has put the switches in the console for the heated seats, but is there something else that needs to be added, or should the seat heaters be "plug and play"?

 

If the heaters are working, what is your question?

 

The heated seats are plugged in but don't heat. I'm wondering if there is a relay or some auxiliary wiring that may still need to be added.

 

I would assume there are a fuse and relay for them. Maybe two. You might want to check with the dealer or other tech about this.