If your Vehicle is fitted with an amplifier from the factory and you want to install a new head unit, it is advised to bypass the original amplifier. The connector in these vehicles when you remove the head unit will look like that shown in the picture on the left, but there are two different head unit to amplifier connections at the amplifier depending on the car.
Some amplifiers are installed in the foot well and some in the glove box. Once you have located the original amplifier, you need to identify the speaker connections out and check to see which plug type is used. Either PC2-70-4 or PC3-300 will be required.
Both PC2-70-4 and PC3-300 have normal power supply harness such as PC2-08-4 or PC2-50-4 but long speaker harness ~ 1.2m, to plug into the speaker out connector of the original amplifier. By connecting this lead into your new aftermarket head unit, you allow the new head unit to run your original speakers directly.
Although PC9-402 is also available to connect the new head unit to the original Amplifier, we do not generally recommend these leads as with head units of more then 35w output, it can cause the original amplifier to cut out.
Amplifier Bypass lead Apr 89 - Aug 93 FD2007
Amplifier Bypass lead Mondeo/Galaxy/Escort/
Alhambra Jul 96 - Oct 97
Sharan Jul 96 - Oct 97
On Ford Galaxy, amp is located just below the head unit, silver box, undo screws from the Top of amp, rear of the amp with cable connections tight against Vent unit.