Perkins 4108 diesel engine wiring harness and diagram

The front face of the original Perkins 4108 control panel,which is fitted with VDO gauges,oil pressure,rev, counter and water temprature,charge warning light,I have added an instrument light on/off switch and a remote cockpit 12volt supply plug.



My own boats engine is a tried and trusted Perkins 4108 diesel engine,its done around 1750 hours,which is not a lot for an engine around 25 years old? I service it on a regular basis and alway use the correct grade of diesel engine oil,this in itself doubles the permisable hours you can run between service over conventional oils.

My engine has what I think is the standard switch panel and related meters,the start switch had been changed for a non marine quality one,I put a new switch in,which in my case has the optional key position to warm up the Lucas fuel pre heater device used for cold starting.

The wire loom is original,it has two cable bullet connectors at each end of the loom,which in my case is about five meters long ( 197 inches) my connector blocks show some degrade from its previous service life,the 4mm brown live supply connector has corroded right away,requiring a reconnection.I also find a few stray wires that seem to connect to nothing,plus wires that are in the loom and are not required.

In my case I have decided to remove and re make the loom as close to what it should be as possible but to remove the bullet connectors, those unused wires and make the loom diameter smaller and easier to feed.I have sourced all the various cable thickneses and colours and will re make the new loom in the next few days,this will lead to a description of what each wire does and what its colour should be,the new loom then has no breaks in it,checking the connections at each end is an easy job and no worries will exist about faulty bullet connectors.
Note,if you do a circuit check your self using a meter will not begood enough,you need to use a large load such as a light from a car which is in circuit with the test cables,if the light does not show full power,you have a bad connection?

Note: the original loom had a Generator,mine now has an Alternator,some of the original wires to this connection will have been changed,please also note that in parts of the original loom,2.5mm diameter wires become 4mm diameter after the connection joint,some colours also change too,making it impossible to track where that wire comes out when using the colour codes only!

Wire colours:

This is what goes where,you may well find (you will) that a certain wire stops and its connected to nothing,plus some small gauge wires become larger gauge once in the main loom,some colours may change one end to the other too,its nonsense when trying to work from the switch panel to the engine what wire feeds what?The standard loom I had was seven meters long,thats about 23 feet.

Key Switch

Brown 4 mm gauge
Blue/Purple 4 mm
White/Red 2.5mm
Black 4 mm
Brown/Yellow 1.5mm

Revolution Counter

White/Green 1.5mm
Black/Blue 1.5mm
Black/Brown 1.5mm

Water Temprature

White/Green 1.5mm
Green 1.5mm
Black 1.5mm

Oil Pressure Gauge

White/Brown 1.5mm
White/Green 1.5mm
Black 1.5mm

Your engine may also have oil and water temprature sender units,these wires will be 1.5mm and in any different colours,probably two wires to each sender but some senders have just one terminal and use the block as an earth,so just one colour in that case.

Note,we can supply the correct colours (as above) in kits and in wire lengths of ten meters,thats about 30ft long,please email me for prices,we can ship world wide.

Roy kits@comlumber.com