First I'd like to say thank you to the members on this forum. I've gotten help off of here many times and it's saved me a ton of time and money. I finally joined because my issue seems to not be too popular. Here's the background.

2008 F350 XLT. I got the power seats out of a Lariat and the manual HVAC control with the two heated seat buttons from the dealer. I have the wiring diagram for the manual HVAC controls and all the wires, fuses and relays are present in the vehicle. When I push the heated seat button on the HVAC control the red light comes on. The diagram states the wires for the seat heat are White/Blue for the driver's and passenger's grey/yellow. When the button is pressed there is no power coming from either of those wires out of the back of the HVAC unit. Again the light does turn red so one would assume the switch is hot. I traced the wires into the fuse box where they enter and exit and then dead end into a large plastic connector. This is where I ran the switch wire from the seats and I'm ready to connect them when and if I get power from the controller. I thought the computer might need to be flashed so I went to the dealer and the service writer looked at me like I had 3 heads. He said the entire computer would be re flashed and it's done by VIN number. If mine didn't come with that option then it wont work and if I sub another VIN I will get other options that I don't have and codes etc. As far as I've taken this project it seems like it can't be this difficult. Up lifter switches or aftermarket are not for me. Does anyone have any insight?

Thanks,
Bill

 

The only diagrams I have are these for a 2006 from Autozone's site. Here's one.
http://repairguide.autozone.com/znet...3f8023b947.gif

In this diagram there is a control box, and I am assuming it's mounted under the seat. It needs two power sources, one large 30 amp power all the time and a smaller 10 amp circuit that is key on power.

I don't know how the 2008 is wired, but I do know anything with a heating element is going to take a lot of power. You should have a heavy circuit with a large wire feeding each of your heated seats. If you figure where it goes you may need to come straight off the battery to feed it.

 

bumping an old thread... did you ever get this figured out? I also have a 2008 XLT with manual seats/analog heat controls. I bought a set of power/heated seats out of a 2008 lariat. I manually wired up the power seats already so they work. Now i'm trying to make the heat work. Anyone have any input?

 

Here is the actual 2008 F-350 seat wiring diagram, if it helps.