I finally got a chance to work on this.
We've had one real snowfall so far this winter, so it's been cold enough to encourage me to work on it as soon as I had some time.
I had about and hour and a half available to me this afternoon, and it was above freezing, so I gave it a shot.
To start with, a Gen 2 Prius has four 14mm bolts that hold in the driver's seat. There was plastic covers over the two back bolts, but not the two front ones. Those covers were easy to remove and set out of the way.
The bolts came out pretty easy. Always a blessing. In my experience, on any older vehicle, 3 bolts holding in a seat will come right out, and the last one will not…. ever. If it can, it usually involves cursing and a can of MAP gas.
With the bolts out, I could tilt back the seat to see the wiring under it. There was 3 stock cables going under the seat. I assume the yellow one was for the airbag and the other two are probably a seatbelt sensor and a occupancy sensor. There was one other wiring connector that looked very after-market, with one red and one black wire.
I unplugged all the cables. They all came apart pretty easily. I then took out the seat, so I would have room to work.
I tested the heated seat power connector with my multimeter. There was no power there whether the car was on, off, or on "accessory" mode. The black wire was grounded to the car body under the seat. The red wire ran away to under the carpet, and then beyond that it was covered by interior body panels.
I poked around under the dash until I found a "one of these things is not like the others" red wire going to the small fuse panel near the parking brake. I pulled it down to where I could see and work on it. The red wire tapped into the fuse box in an interesting way so as to replace the fuse AND pull power at the same time.
I followed the red wire back to…… NOTHING! There was a 1/4-inch spade connector with nothing where a wire should have been. Obviously, a bad crimp had been made by the original installer. I pried away the interior body panel directly below and found a 7.5a in-line fuse holder, with a bad bare wire end. The other end of it disappeared going the direction of the drivers seat.
I trimmed the end of that wire, stripped it, and crimped a new 1/4" spade connector. With that in place, and the fancy red wire with the fuses built it plugged back into the fuse box, I tested power under the seat and finally found some; 14.21VDC.
I put the seat back in place and plugged everything in. I then tested the seat heater BEFORE running all the bolts back in. It tested fine. It does indeed have power with the car in the ON or ACCESSORY position, but NOT when the car is OFF.
While the seat was out, I examined it, looking for any loose wires, scorch marks, or worn insulation and didn't see any similar problems.
The whole thing took about an hour, and didn't require any more skills and materials than simply testing for voltage with a multimeter and making one electrical connection crimp.
Whew, it was one of those rare occasions in auto repair where everything went right!
The seat heater works now…… which makes my wife happy….. which makes my life easier!
By using a block heater for the engine, and a seat heater for the driver, I can force the car to EV mode AND not freeze to death. Getting 3000 MPG in a Wisconsin winter is a pretty cool trick.
I'm still limited by the front defroster kicking on the engine. I may have to resort to a 12V Harbor Freight dashboard defroster!
Anyways, so long as my wife is happy, everything is good.
Today
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