From time to time we hear of 12 volt coolers power cords melting. In many cases there is a very simple reason for this and it has nothing to do with the cooler cooling mechanism failing.
The reason for this power cord failure has been determined to be an over-draw of amperage. This is typically caused by a bad or loose connection in the lighter socket outlet.
When dealing with power whether it’s AC or DC power, wattage is determined by volts x amps. The effective voltage is reduced by a poor connection, so to make up for this the amps will increase until the fuse blows or the plug melts. This occurs naturally as the cooler demands a certain amount of power for operation.
The solution is to ensure a tight fit of the cooler power cord in the vehicle’s lighter socket outlet / accessory power port, or by hard-wiring the cooler power cord into the vehicle’s 12 volt power system.