Hello, Is the 2007 the Ford E250 referenced in the this question?
If so, then there would be no sound from the speakers when one of the speaker wires is pinched/kinked or some how shorted to ground (the chassis of the vehicle). Additionally one of the speakers having a shorted voice coil (being blown or dry rotted), will cause this.
You will need to remove the speakers and test them with a multi-meter. Each speaker should have a DCR of close to 3.2 ohms. If either is much lower than that- or a dead short, that speaker is putting the radio's outputs into "protect mode" to prevent damage to the radio.
If the speakers test fine, then without the radio connected, use your meter and test each terminal of the speaker wires (at the speaker side) with reference to chassis ground, and see if one show continuity to chassis ground. If it does- then you've found your culprit.
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