I recently upgraded my speakers and immediately noticed that the back ones were underpowered. After about a week I noticed there was no sound coming through at all. While checking the doors, I discovered that the switches don’t work either, though I can still operate the windows using the front control panel. I've searched online but haven't found any information explaining this bilateral issue. I suspect it may be a fuse problem, but I haven't identified the specific fuse causing this. If anyone could refer me to a relevant thread or provide information on how to fix this, I'd greatly appreciate it!

 

You said the switches don't work any longer while checking the rear doors. What switch, door lock + window combo switch or door ajar switch or both? Both rear doors?

 

Okay, I figured out the window issue. The window lock was gummed up and stuck halfway in the off position. Didn’t fix the issue with the speakers, but definitely is a little relieving. I checked it yesterday!

So knowing that it’s not a power issue, what might cause the rear speakers to go out? I checked their harnesses and the connection is solid all the way through the grommet.

 

To my understanding thus far, you upgraded the speakers only, not the wires. How do you know your wires are capable to handle the upgraded speakers?
You checked the harness and connection at the grommet visually, but you didn't check for bad wiring.
What I would do, bench test the speakers or test by running your spare new speaker wires or electrical wires if you don't have any spare speaker wires directly from your stereo to the speaker and bypass all your existing wires, then you can tell if you need to replace or upgrade your speaker wires to the rear.

 

Dang, I was hoping you wouldn’t say that. I’ll get on that tomorrow morning and I’ll see what I can figure out. Thank you!