OEM Heated Seat Retrofit problem

So I've got a 1998 GMC Suburban SLT. It came factory with leather power driver with all the options except heat. The passenger seat only has lumbar support on it.

I found a '99 Tahoe SLT that had full power, heated, leather lumbar driver AND passenger seats in decent shape for $100 for the pair. I bought them. Well just got home and realized the electrical plugs for the seats are totally different than the ones on my truck.

I foolishly assumed it would be the same exact wiring harness across the board like GM does 90% of the time on these trucks and that they'd be plug n play. Well they apparently aren't. It appears that I am also missing wires on the connections coming out of the floors on both sides.

Has anyone tried to do this swap before hat can provide a little insight as to what I need to add or do to get these to function?

New passenger seat wiring harness (5 contacts much wider connector)


Existing passenger harness (2 contacts narrow connector)


The driver side seats share the same same connector but my existing one is missing a contact. I assume for the heater function since that's the only option my existing driver seat doesn't have that the new one does.

So after looking some more the heated seated feature has its own fuse locations in the fuse box under the hood.

It's got 20 amp fuse slots for the front and rear heated seats if I had those and then another 40 amp fuse slot that just says "heated seats." It appears it's more trouble than it's worth to make these function like factory. The fuse box doesn't even have the pins for it so I'd need to get the wires needed, pin it into the fuse box and then run the wires through the fire wall with the main harness and into the proper connector. Or go back to the truck I pulled the seats out of and take its fuse box and harness from the fuse box to the seats and swap it with what I have.

I'd say go back to the donor truck & grab that stuff.

It looks like I'm going to need to. I'm looking at some wiring diagrams though, granted I'm just learning to understand those, but it looks like quite a bit of harness I'd have to get and reroute through the truck.

Could anyone tell me if these are independent harnesses for the seats. Like if I went back and got the harnesses from the donor truck would it be as simple as pinning them in to their appropriate fuse block spots and just routing it under the carpet and what not. Or do these also tie in to other things that would require me to remove the dash to rewire stuff there too. I can't tell if these are like full body harnesses or just wires for the seats. I don't want to have to rewire the whole truck just for some seats.

My seat heaters don't work.
Haven't since I got them. No matter. I have a bit of an aversion to them, due to the fact that I've been inside these seats and have seen what happens when they malfunction.
But, for the power for the tracks, I grounded them to the body & pulled the power from the distribution block for the amps.
I only needed 2 of the 4 outlets for the amps.
Not fused because of the amount of time that the power is used to adjust the seats is minimal.
10 years & no probs.
But, I would definitely NOT do that for the heaters due to them drawing power over extended periods.

Yeah the whole reason I bought them is for the heaters. I think I'm going to try and go back to that truck, pull the front carpet up and see where the seat harness traces to and find out how much I actually need

when I stripped a '99 Tahoe, I found the following: the harness to the seats is a large harness.
it goes the length of the dash, down to the door harness union in the kick panels, also had a section come down the transmission tunnel which had the seat plugs & the section holds the bulbs & goes into the floor shifter (which this truck did not have), a section went to the keyless entry module, a section went to the mini amp, a couple of plugs went to the column area, a section went to the main harness to meet @ the firewall, a section went to the airbag module under the seats & the last section goes along the driver side under the sill plates ie: speakers, 3rd brake light, dome light.

my truck is a '99 c3500 cclb & I gutted a '99 Tahoe to do a pwr window & lock conversion. I ended up gutting the airbag & lojack stuff as it wasn't needed for my truck. Tahoe doesn't have a cargo light & the union plug in the sill plate was different as was the dome light plug, under the dash & door ends were the same other than my truck didn't have the amp or keyless entry stuff.

needless to say its a little time consuming to get the whole harness.

I think I'd probably just keep it simple and run a relay to some 3 position switches and be done with it.

This seems like a real hassle and sadly no one seems to make an aftermarket seat heater that fits the cuts in the 95-99 obs seats. I’ve wondered if the Dorman kit might work if placed under the foam, if any heat can migrate up through the foam at all.