I own a JVC MX787-V model. I have a problem with the volume control knob, when i turn the knob to lessen the volume instead in increase the volume. What must be the problem.

SOURCE: volume knob

In other words the lever that the front knob is attached to is broken or the microswitch is bad or broken.. if your not a tech please take the unit in to a shop as there are no user serviceable parts inside these units. Good Luck

SOURCE: volume control problem

bring good contact luricat cleaner from near radio shack and apply it over volume and move it forward and backward many times.

SOURCE: Honda Civic Issue with Radio Volume Control

This is a known problem with the factory units and no, there is no fix. There is a series of checks you can do, but short of that the only option has been to replace the unit. I have included the graphic for the checks, other than that it is not fixable.

SOURCE: Volume Control

The volume control shaft lube, over time and heat exposure, will flow down and corrupt the contact between the volume twister and the spring loaded sensor. Pull the cover off the tuner, locate the volume control and take out the two screws holding it in. It looks like a small circuit board with the volume twister attached.
The base of the twister is hooked to the circuit panel by four metal tabs. Pry these guys gently away and pull the twister free. There will be a metal disk at the end of the volume control shaft, and will have a goopy lube residue on the face of it that can be cleaned with electric contact cleaner or some other kind of solvent. Wipe it clean,(do not immerse) reattach, and test. Worked perfect for me.
Good Luck,
F

SOURCE: Car radio volume control knob is erratic

When I turn on my radio, the volume is on and o.k. but when I try to turn it higher or lower the volume is lost completely. Any comments?