Used 12v socket located in cargo bay of '98 ML 320 to power a 12v cooler. Everything worked fine and then suddenly the cooler quit. At that point the dealer-installed GPS failed to power up and the lighting for the rotary dials of the climate control (blower speed, etc.) was noted to be inoperative.

Now, a week later, the radio fails to shut off after removing the key from the ignition.... the radio will literally play for hours until manually shut off.

All fuses in the engine compartment fuse box are intact and there are no relays listed that would appear to be responsible for the GPS power.

Any fuseable links on this vehicle? Perhaps another fuse box, not located in the engine compartment? Where does the dealer-installed GPS tap into power on this vehicle? Does the GPS power line have an in-line fuse?

Safe to assume the radio problem is separate from the GPS/lighting problem?