Seat warmer turns on automatically

That's the part I can't figure out either. It's intermittent, and usually if it happens, it happens 30+ minutes into the drive on a long drive. And it's been going on since at least June of last year. (Got the car in April, 2018.) But because it's intermittent, it goes away for a few weeks, up to a month, then I kind of move it down the priority list. But it happened again this week, and now *my* relay is about break.

If you've ever put a heating pad on your shoulder or back and left it on too long and start to feel that burning sensation after a while, that's it.

I've also done all of my TSBs. None helped.

One other possibility: could it be that the key fob is moving around in my pocket, and somehow the preheat button is getting hit?

Or a problem with the keyfob receiving unit? Because the other main problem I have with the car is that doors only lock about 50% of the time when I walk away. I *have* to mash the button to make sure the doors lock. If I rely on the key fob/car to do it as I walk away, it's a crap shoot. And coming back to an unlocked car is a terrible feeling.

 

AFAIK, preconditioning involves only the electric resistance heater and fan. I wonder if there's a way you could monitor the current through the fuse to sound a beeper? Assuming the relay always lights the LED when it powers the seat heater, I'm having trouble imagining a circuit design that can send power to the seat heater without lighting the LED. It must be bare wires that were never meant to touch, touching--an ad-hoc circuit, as it were.

 

Got my car back from the shop today, and while the tech could not reproduce the problem (it only happens to me 2-3 times a month, but it hurts like hell), he reasoned that it was most likely the seat heater control module, since a TSB had already swapped out my climate control unit in January. He also tested the front seat wiring, and didn't find any faults, so the most likely culprit was a bad control module.

From what I understand from talking to him, when you press the seat heater button, the switch sends a signal to the climate control unit, which then turns on the light and sends a "turn seat heater on" signal to the seat heater module, which then closes the circuit under the seat, warming it up.

A rogue/malfunctioning seat heater control module would just randomly turn the seat heater on, maybe thinking it got a signal from the climate control unit, maybe just generating bad data all on its own and closing the circuit under the seat. The problem is that now the climate control system doesn't know about the rogue module, no error code gets stored, and the worst part (for the person sitting on top of the seat heater) there's not really a way to control it if it's bugging out. So the heater stays on.

At least that's the working theory as far as I can remember from my conversation with the tech.

Just putting it in this thread in case someone else ever has this problem. According to Honda, I'm the first. Woo hoo. Lucky me.

Tomorrow I have a nice 4 hour drive to the mountains, so it'll be a good chance to see if we got it.

 

I'm amazed how complicated a seat-heater can be! So it IS possible for the seat heater to be active while the indicator LEDs remain unaware. Here's a back-up plan from Walmart:

 

Yeah, either that or I go find a square of Nomex to sit on. I've seen those around somewhere else, too, maybe at a truck stop? I almost bought one, too.

 

If Honda had instead shipped your car to @MNSteve in frigid Minnesota, the problem would never have been discovered.