Peugeot alternator part numbers suggest that all petrols (1.4 and 1.6) use EITHER a 70amp (5705 6C) or 80amp (5705 AW) alternator. Diesels appear to have 150 amp versions (5705 A5)

Basic battery check

Although I have sophisticated test gear, I use a  car cigar 12v battery voltmeter  for a quick check. This simple meter should indicate around 12.3 volts with ignition on but engine off - rising to around 14.3 volts with the engine running.

This is the wiring schematic for the starter/alternator/battery

The battery condition is critical (I recommend change every five years) but an increasing number are reporting Alternator problems. The alternator is also connected to the Engine ECU which controls the output voltage.

This is known as  "SMART CHARGING"  and replacement batteries should be of the Silver Calcium type.

 Basic "How Battery Charging Works" 
 Basic "Smart Charging System" 
 Layman's "How Battery Charging Works" 

Engine dies or gearbox is erratic

The alternator is controlled by the main computer and is not an independent device as in the past. When the alternator stops working the battery volts start to drop and the systems interface will start cutting out the high demanding systems - like air conditioning - until it stops operating the electrical throttle body and finally cuts out the engine.   If the voltage drops below 12.4 volts you will have problems including the 2-Tronic shifting.

Changing the alternator

The alternator is a tight fit so some patience may be needed! Some remove the front wheel and mudwing which gives easier access to the end bolts, however most will do it this way:

note that "left" and "right" below relate to standing in front of the car looking towards the engine. Also that the bolts are 16mm so make sure you have the right spanner sizes.

First - Disconnect the battery

Turn the bolt at the centre of the tensioner pulley with a spanner to release the belt tension and remove the belt from the alternator pulley

Remove both left-hand fixing bolts (16mm)

Dismount the expansion tank which will allow the flexible pipes to move and create more space to extract/replace the alternator.

Undo the 4 bolts holding the heat shield over the exhaust manifold and remove it. This improves access to the top right-hand alternator bolt

At this stage it may be worth moving the front panel forward slightly to aid removal of the alternator

1. Hook & screw: remove screw and lift panel to disengage from hook.

2. Remove this bolt.

It should now be possible to pull the left-hand side of the radiator assembly forward to make just that little extra clearance that turns a difficult job into an easy one.

Slacken the alternator upper right-hand mounting bolt (16mm) using a socket on an extension bar inserted under the exhaust manifold from the right-hand side. Slacken sufficiently to reduce the grip of the expanding collar on the mounting.

Loosen the lower right-hand alternator bolt from under the car. Feel the head of the bolt and then put the 16mm socket over the head of the bolt and then clip the socket spanner in place to turn the bolt. Again, slacken sufficiently to reduce the grip of the expanding collar on the mounting.
An alternative method of getting to this bolt after the top bolt has been removed, is to use a breaker bar in between the alternator and bracket and lever it downwards to expose the bottom right bolt, making it possible to remove from the top.

Slide the alternator leftwards, the expanding bolts just fit between the mounting brackets so permitting the alternator to be disengaged from the brackets.

Completely remove the expanding bolt assemblies

Manipulate the alternator and remove it vertically upwards from the engine bay [see picture for orientation]

Refitting the alternator

The replacement alternator may be slightly different to the original, so take the precaution of removing the exhaust heat shield and dismounting the coolant expansion tank to enlarge the gap through which the alternator has to be squeezed. It may also be necessary to trim a few mm off the black plastic in the corner of the engine bay [see picture]

After the alternator is squeezed through the gap, reposition the heat shield but leave it loose.

Refit the expanding bolts to the alternator after manipulating into the approximate position in engine bay, but before offering up to the mounting.

Tighten the alternator mounting bolts and refit the belt, holding the tensioner back with a ring spanner.

Bolt the heat shield back into position and refit the expansion tank

Aud Trev Thawley: a WARNING note for anyone attempting the job. The two obvious bolts at the left of the alternator are easy to get at and undo after removing the front drivers wheel and wheel arch trim for easier access.

As for the right-hand ones .......... I thought these were just studs that the alternator located on. However they are actually split sleeves with a tightening bolt that would have made life much easier if I had loosened the bolts first.

Although access to the back is tight, no special tools are needed. It is just a case of loosening the bolts off which then loosens the split sleeve. The alternator slides off and pulls the split sleeve complete with the bolt through the casting

Sonjia notes that it is possible for the alternator warning light to stay on if the ignition key hasn't sprung fully back to the "run" position after starting. Bit of lubrication on the lock and its been fine since.