I have a 2500 Ram and when the engine is running only the rear speakers work, but when the key is in the on position without the engine running front right speaker works and left is intermittent, sometime yes sometimes no, and both back speakers work. I've already switched the two front speakers so I know they both work. Any suggestion as to what to check.

 

You have the infinity sound system on yours?

Moving this to the correct section.

 

It's the stock am/fm radio with a cassette that came with the truck.

 

New update on radio. If I turn the radio off then start my truck the front passenger door speaker and the back speakers work but driver door speaker is still intermittent. Never have put a cassette in the cassette player to see if it works or not I'll see if I can get one and see if it and all the speakers work when the cassette is playing.

 

Could possibly be a bad ground in the speaker system. Or the internal amp in the radio could be bad. If you have a spare aftermarket radio kicking around, I'd buy the harness kit and the dash kit to try that out. I know a Saturn isn't the same but I had that issue in it and I swapped the radios and it worked just fine after. But definitely check the grounds before hand, especially if that speaker is intermittent.