I suspect a WATER LEAK!

Hey all, first post! I recently bought a 2004 Sequoia from my uncle, and since then, I've had electrical problems one after another. I'm a mechanical engineer and am not very electrically-minded at all, so I've been dreading doing any sort of electronic troubleshooting.

Just a summary of some of the issues I've had the last few months:
- Fuel gauge shows empty and the fuel light shows on dash -- happens once in a while
- Radio get staticy when I make a sharp turn -- maybe 50% of the time
- Radio get staticy and/or switches channels (while still displaying the intended channel) -- happened once for a few days during a heavy rain
- "A/T fluid temp" light on when just casually driving, and in 20 degF weather -- happened once
- Fan did not work for one drive cycle -- happened once
- Heat does not work, but I think I've narrowed it down to the heater core, maybe a blockage. Or maybe it's leaking fluid on other electronics stuff and causing the mystery issues??

Any ideas? I don't want to tackle this alone and in the freezin cold!

 

Definitive 2000-2006 cab-area rain water leak thread | Toyota Tundra Forum

 

Lots of ideas and they're all in this must-read thread: https://www.tundras.com/threads/so-you-wanna-buy-just-bought-a-1st-gen-tundra-eh.115928/

But I suspect the RED TEXT here, taken from inside that thread, is very high on the suspect list. Especially if you're the kind of person who mistakenly thinks windshield cracks aren't something you need to fix, or you're dealing with other A-pillar/windshield leaks.

• These trucks usually don't have a ton of other electrical issues. Hidden corrosion inside the battery/alt cables happens. Sometimes, a couple thousand miles after timing belt changes, people will have startup issues because the crank position sensor wasn't properly tucked away and gets rubbed by a belt (pic), correct routing info here. There's also a similar problem with camshaft position sensor under the cam cover, where the belt will rub through (pics). There's the rodent issues mentioned earlier. Occasionally, water leaks can send water down into the ECM behind the glovebox (pics), or into the fusebox inside the cab/dash (pics & pics & pics, it happens a LOT). Many drain/vampire issues trace back to aftermarket add-ons whether the owner knows they exist or not - alarms as mentioned earlier, brake controllers, poorly installed trailer receptacles, those are some big ones.

Multi-circuit glitchy things are often a result.

While the fuel level is a byproduct of resistance from the fuel sender, the fact you have a couple things linked to RADIO circuit, a couple things linked to GAUGE circuit, that raises an eyebrow.