Power Seats - Part 1 (Dash Wiring)

I have seen a few write ups on power seat installations, but nothing that I really liked.  I saw a few where people had run wiring from the fuse box in the engine compartment through the firewall and a really didn't want to do that.  I wanted to utilize the factory wiring as much as possible.

The S10 Pickup truck did not come with power seats.  It was not an option.  However, the S10 Blazer did and it shares wiring with the pickup.  So I went to the local junkyard and found a 2003 S10 Blazer that had power seats and went to work trying to figure this out.  I found a wiring diagram online that shows an orange wire in position B1 that provides power from the body relay block to the seats.

I found the body relay block.  It is located about halfway between side of the truck and the steering column.  I took a screwdriver and pried on the clip and pulled down on the block.  This released it from the clip.  The picture below shows an example of the clip along with the correct location of the screwdriver used to unhook the block from the clip.

Once out, I needed to identify the wire I need.  The block is not lettered or numbered, but I figured out the pattern in that Columns A-F are the short side of the block and Rows 1 through 12 are the long side.  The 10 gauge orange wire is found in position B1.

Yes, I completely cut the old harness out of the Blazer. I needed to for the purposes of this document. Note: DON'T CUT YOUR HARNESS IN YOUR TRUCK!!!! you don't need to.  Unbolt the harness from the body relay block using a 7mm socket.

Once removed, use a small screwdriver or pick to remove the blue clip that provides extra support for the wires in the harness.  Remove it completely.

At this point you can use a pick to pry up the terminal lock (circled) to remove the orange wire.

I removed the orange wire and inserted it into my existing connector in position B1, which was obviously empty since I had no power seats to begin with.  I reversed the processes outlined above to insert the wire into the connector.

Now this is the most important part.  I had to use the Blazer body relay block.  The S10 block will NOT work.  Even though there is a provision for the power seat circuit breaker, it is not connected to anything.  This is very noticeable.  The circuit breaker will just fall out of the hole if it is turned upside-down. Below is the S10 pickup body relay block with the power seat circuit breaker provision circled as well as the part number.

I made sure to use part number 15319605 (circled).  This is the correct body relay block for a truck using power seats, power windows, and power mirrors. It already had a 25 amp circuit breaker (circled) in place.

I slid the "new" body relay block onto the clip located behind the dash and bolted my connector to it. I bought some additional wire to use to power the seats and will discuss that in Part 2.