intermittent dinger affects radio left speakers on 2004 Chevrolet Silverado 1500

My dinger is intermittent but the problem is that when the dinger don't work, the radio left speakers don't work either!

Check the door switch, just a guess but they will allow the dinger to work when the door is open and the radio to operate with the key out until you open the door. It's probably sticking.
The door switch on this 2004 must be inside the door panel on the end of that black rod that moves in and out. I have another little rod on the back extended cab door that doesn't seem to do anything, so it must be on the end of the rod. Couldn't find another switch anywhere....

I'll check that out and see what gives....thanks
Is there a button switch on the end of the dash?
Not that I can see. The door is about an inch or so from the end of the dash. I don't know where it might be. I think the black rod that goes into the door may be what holds the door open. This truck is a 2004 Silverado LS, if that might make any difference. Thanks again for the help.

I'm thinking of an earlier GM truck then. Just to clarify, when everything is operating normally, does this have a feature where when you turn the truck off and you take the key out of the ignition the radio continues to play until you open the door?
Yes it does, for about, maybe, 15 minutes. I stopped at one of the local Napa stores here, he used to work for Ford, and we have about decided that it must be some module, either in the computer, or between the computer and door switch. We think the switch is integrated in the door latch. I suppose I can remove the door panel again and check for wiring from the latch.

Now what we did was trip the door latch, and the dome lights went out with the door open, but the dinger and radio, on the left side front, are still inop in that condition. So we reset the door and I went on to where I was going.

Thank you again for the help