Radio volume automatically goes to lowest

[jg621]

Need some help. Bought a used 2003 Disco and the previous owner installed an after market stereo. I purchased the factory unit and installed it. It is working fine if I hold the volume knob in place, but when I turn it up the Radio volume automatically goes to lowest setting. Seems like someone is holding down the volume down button on the steering wheel but it continues to happen with steering controls disconnected. Any thoughts?
Thanks in advance for your help.

 

[joey]

Did you buy this radio as a new unit or used? Sounds like the radio is having issues.