The battery on my wife's RX-7 was dying, so I replaced it today.

I started it up and it ran fine and I shut it back off and all was normal.

Then my wife drove it on some errands and had some trouble. Every time she shut off the engine, the rear heater would turn on and run for a few minutes and then turn itself off.

I tried it myself, and sure enough: Turn on the engine, it runs fine, turn it off, and then the rear heater comes on. Weird.

I tried disconnecting and reconnecting the battery to "reboot" the car, but it's still doing the same thing.

Any thoughts?

 

What year is this RX7? And are you talking about the hatch defroster?

-Sheldon.

 

This sounds very much like a similar problem cropping up in the CX-9's.
See if the relay is stuck and needs some persuading, and or needs to be replaced.