99 Denali Heated Seat Question

[ultara]

I replaced the worn seats in my 97 Tahoe. It had power seats but no heated seats. I found a full interior from a 99 Denali at a junk yard. I now have power/heated seats (both front and back) but need advice on the wiring. The new seats will plug in (same plug configuration) but I have an extra small guage brown wire that I assume is for the heaters. I cannot find the appropriate wire schematic to identify the correct power source, if in fact this is a power wire. I am assuming this is a relay activation wire because of the small guage. I don't need to start a fire in my seat, so I am investigating before connecting. The wiring from the center council to the rear seat heaters is a problem for another time.