so my seat heater doesn't work in either front seat. but when I hit the switch sometimes i get nothing. sometimes i get a buzz under the dash. I have searched the forum, but i couldn't find these symptoms. I may need to put new heaters in the seats, but I'd like to rule everything else out before I start removing upholstery...

 

See attached drawing from RAVE and photo of seat bottom. A litle hard to get at connectos and headers (splices), becuase they are under seat or under center console. So FUSE 15 should be checked, it runs seats, vanity mirrors, and cigar lighter. If you removed fuse 15, the two point in the socket it came out of will represent 12 volt source (main power) and the loads. With volt meter and fuse out, measure for volts from each side to metal frame (earth) of truck. Key will have to be in position 2. The side that has no volts is what we want.

On the "cold" side, measure for ohms to earth ground. Should read "open" or "infinity". Push in cigar lighter. Should see a change. Meter won't make enough current to pop out lighter, so just remove lighter.

Now operate seat switch one by one. Should also see a change. If no change, then time to see if you can reach connector under seat, and meter again from that side to metal frame. We are trying to see continuity from heater element to earth ground. Note that butt and back of seat are two elements, in series, so both have to be good to have a reading.

An alternative to going under the seats is easing out the center console switch bank, and metering the blue & slate colored wires off the seat switches to ground.