ISO is the international standard connection used by all radio manufacturers and fitted in all new radio harnesses (female ISO). When installing a radio these need to be connected (by push-fit) into an ISO male.

Some cars have ISO male connectors fitted to their radio harnesses as standard and this will enable you to install your radio in minutes without any problems. If you don't have an ISO connection as standard this isn't a problem. All you will simply need is a harness adaptor (unique to your car model) to convert your car’s standard radio harness to fit together with the ISO on your new radio.

If the male connector on the car fits the female connector on the radio, they will simply click together. There is an exception to this rule, as some cars, mainly Vauxhall and VW models require a small alteration to their power input configuration.

If you were to connect the ISO plugs, the radio would work OK, but once you turn off the ignition and remove your keys the radio would lose its memory settings (stored radio stations would be lost and any inserted CD's would be ejected). This is due to the power wires (yellow: permanent live and red: ignition live) being connected the wrong way around, for these particular car models.

Many radio models now come with harness adaptors that use bullet connectors in line with the harnesses power wires. You can simply disconnect the bullets, switch the yellow and red wires and reconnect.

Or, on some older cars, if the radio is connected as permanent live (can be turned on without the key in the ignition). In such cases, you may have to connect the yellow and red wires on the radio lead together. It is possible, where the manufacturer’s radio wiring allows it (using bullet connectors that are inline on the radio harness), to line up with the permanent wire on the car’s harness. This means that when the two ISO connections are pushed together the power is transferred to the correct wire positions.

Article Source: http://EzineArticles.com/?expert=Chimezirim_Chinecherem_Odimba