Something Finally Broke on my 2007

Might be a loose wire/solder area on that switch?

 

We had a spring stop being springy in the top glove box. These things happen.

 

Search the Gen II audio and electronics forum and you'll see this is a common problem. Dont recall anyone having a fix for it other than replacing the radio. If you're still under warranty Toyota will replace it. If not, a radio from the dealer is expensive but salvage units on ebay are relatively cheap. Still others propose putting in an aftermarket unit. Good luck.

 

Sounds like it could be corrosion on the volume control's wiper contact. This was very common with older radios and other consumer electronic systems, especially in smoggy or smoky areas near factories or refineries, or high salt foggy air like the Bay Area. Your saying that it works for a while after twisting the knob repeatedly clued me to this conclusion.

Years ago, the only solution was to disassemble the radio and spray contact cleaner into the control which would clean off the corrosion. However the radio in the Prius is probably so tightly packaged that you can't even see the control, let alone get to it. So the earlier response of "replace the radio" may be the most practical, though not the least expensive. The steering wheel volume controls sound like the best and least expensive solution.