Dim Lights

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Original submission made by T Dec 25th 2005:

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530 CCA Delco Battery after 6 trouble free years of use in a daily driver UC Torana even though the Engine is a 202 with a 173 head which gives the cranking system a real workout. Note the grease smeared all over the battery terminals and the complete lack of corrosion on them. Click to Enlargen. Photo by T.

Dim Lights, Slow Wipers, Cranky Starters, Undercharged Batteries. Causes and Cures:

Qute has provided some of the finest examples of the relevant wires. The condition these wires are in is a classic example of the state which causes Dim Lights, Slow Wipers, Cranky Starters and Undercharged Batteries. Fuse Cover Thread These conditions are not unique to Old Holdens. If your cables look like most of these they are overdue for replacing. See also Electrical Tips.

Alternator Feed:

This is the large cable that connects the Alternator to the Battery. Any voltage drop across the Alternator Feed is a direct cause of dim headlights, slow wipers poorly charged Batteries. In the example below, a burned Alternator Feed results in the Battery being deprived of the 14V it needs to be charged properly.


The effect of both a burned Alternator Feed and a burned Primary Feed can destabilise the electrical system and combine to produce very dim lights and very slow wipers. When the cables are burned the copper will be oxidised in appearance, the insulation will be hard, brittle and it will have shrunk at the connectors.

Replacing these cables with new ones of the correct current rating will return the voltage drop along them to an acceptable level. Since the Alternator Feed is the hardest working electrical cable (in a normally functioning car, engine running) because the power for every electrical device on the car will come through it, the effect of heat will can cause it to oxidise and need replacing in time.

When the engine is shut off, the battery provides the power. After a start the alternator feed has to run every electrical load as well as replenish the battery Consequently there are circumstances where the car's electrical load, plus the load of the discharged battery can exceed the current rating of the alternator.

At this stage the alternator is described as being in "current limit". Once the battery has been recharged, the current flow from the alternator will reduce and the current flow through the alternator feed will also diminish. As a consequence, the current rating of this cable must be at least equal to the maximum output of the alternator. i.e. If the alternator is rated at 85 amps max, the alternator feed must be rated at 85 amps minimum.

To protect against over current (in the event that a short circuit occurs inside the alternator) the alternator feed should be protected by a fusible link equal in rating to the alternator's maximum current. 3 x 30 amp wires each with a 30 amp fusible would do the same job. As a car ages, this cable can become burned and resistive, due to the load it carries and under bonnet temperatures.

As a result critical voltage will be lost across it and replacing it with new cable will fix the voltage loss. A badly resistive Alternator Feed can cause a glowing charge indicator light because the current will flow up the indicator feed wire from the alternator to the indicator dash bulb.

HZ Fuse Cover. Click to Enlargen. Photo by Mackv8.
HZ Fuse Cover. Photo by BIJ. Click to Enlargen.

202 UC showing extra Primary Feed wires attached to the Starter Tap. Click to Enlargen. Photo by T.
Corrosion under Battery Terminals between the Battery Post and the Terminal.  The corrosion will reduce the Alternator's ability to charge the Battery and the Battery's ability to turn the Starter. The Battery will not integrate the DC Ripple from the Alternator so will result in Audio Whine in the Radio and/or electronic equipment malfunctioning. Click to Enlargen. Photo by ReaperHR.
Lucas Alternator showing the yellow Alternator Feed wire. Click to Enlargen. Photo by Qute.
Fuse Board. The blue connector with the red and yellow wires is attached where a new fused Primary Feed could be connected. Click to enlargen. Photo by Qute.
Battery Terminals must be clean, tight and completely covered in Electrical Grease. If not, ions from within the Battery will be attracted to the Positive Terminal and erode it resulting in an Electrical Resistance there. The Resistance will prevent Alternator Charge Current getting in and Starter Current from getting out. The purple wire is the chassis ground. Increasing the current carrying of this cable is important if extra accessories are fitted to the car. Photo by Qute.
The image shows the Primary Feed and associated connectors on the Fuse Board. Click to enlargen. Photo by Qute.
The image shows the Primary Feed bus. Click to enlargen. Photo by Qute.
Corrosion under Battery Terminals between the Battery Post and the Terminal.  This image shows how penetrating hydrogen ions can be. Caused by lack of grease on the Terminals as the image shows. Click to Enlargen. Photo by ReaperHR.

Generator Feed:

The largest wire that runs from the Generator to the Regulator is called the Generator Feed. Another wire of equal thickness will exit the Regulator and run to the Battery Positive Terminal. Both these wires must be at least equal in current rating to the Generator's maximum output and the Current Regulator must be seet to allow this current to pass. The Generator requires a matching Regulator to work properly and these considerations should be provided for when adjusting the Voltage Regulator, the Current Regulator and the Cut Out Relay. All wires between the Generator, Regulator and Battery must be able to carry the current that will flow through them to allow the Generator to deliver its full output voltage and current. Of particular note is that the Generator Feed is most likely to age and become resistive first. The same requirements mentioned for Alternators hold true for Generators too i.e. the Generator feed must be rated to carry at least the maximum output current of the Generator.

The Primary Feed:

This is the second hardest working cable in any car and early Holdens are no exception. Certainly up to HZ the headlights wipers, ignition, horn, tail-lights and brake lights are all run from it. Any voltage drop across the Primary Feed is a direct cause of dim headlights and slow wipers. The Primary Feed is the lead that runs from the large Starter Tap to the Fuse Box under the dash in Kingswoods and Toranas. Over time this wire becomes resistive and a voltage drop appears there. On Kingswoods and Toranas there are additional taps on top of the fuse box that provide connection for additional Primary Feed wires.It's best to relocate any connectors using these taps to other locations, perhaps direct from the Starter Feed.If the load on the Primary Feed is increased (by adding a hi-fi system, dash fed driving lights etc) it is imperative to uprate the current carrying capacity of the primary feed to accomodate the extra load otherwise the life of the Primary Feed will deteriorate. As a car ages, the Primary Feed can oxidise and become resitive due to the load it has carried and the under bonnet heat.

Chassis Ground Cable:

The Chassis Ground Cable carries all the Body return Current. Lights, Radio, Wipers, Internal Fans, Thermo Fans etc all send their return Current through the Chassis Ground Cable. Starter and Engine Current returns via the Engine Ground Cable.Make sure the Chassis Ground Cable is large enough to carry all the Electrical Load except the Starter Current.I recommend using a separate length of Starter Cable connected between the Chassis and the Engine Ground Cable to make sure the return Current does not cause a large Voltage drop or burn any wires.

The Red Arrow in the lower right hand corner shows the Chassis Ground Cable. This Cable must be uprated if the Ancillary Equipment is increased. Photo by Tom Mitchell. Arrow by T. Click to Enlargen.
The Blue Line in the lower right hand corner shows how to connect the new and larger Chassis Ground Cable. The existing thin Cable can be left in place. Photo by Tom Mitchell. Line by T. Click to Enlargen.
The VB-VK Commodore Headlight Power comes from the Primary Feed Wire which runs from the Ignition Switch. Image by T. Triple Click to Enlargen.
To uprate the VB-VK Commodore Primary Feed Connection, add a second 30 Amp Primary Feed Wire from the Battery via a 30 Amp Fuse and connect it as shown. Image by T. Triple Click to Enlargen.
202 HJ Holden. The Wiring should have been re-routed away from the Extractors. Image by WayneHJOwner. Triple Click to Enlargen.
The Primary Feed Wire connects to the Passenger Side Starter Tap. A loss of Connection will result in the loss of all Power to the Car. See the Broken Primary Feed Wire Threads in the Links Section. Image by WayneHJOwner. Triple Click to Enlargen.
The Green Wire comes from the Battery Positive. It is also where the Primary Feed to the Dashboard connects. Photo by Qute
The Engine Ground Cable and Attachment Point can be a major cause of Electrical Problems if missing or loose. The Bolt is 3/8" UNC. Use a Phillips Impact Screwdriver to tighten or loosen. Photo by Qute.
The Primary Feed on a high time car can easily look this bad. This car would benefit from additional Primary Feeds being run from here to the Dashbord Fuse Board. Photo by Qute.

Engine Ground Cable:

The large cable that runs from the engine to the battery negative. This has to be large to carry  the starter current. It also provides the return path for ignition and any engine sensors (oil, temp etc).

Glowing Charge Light:

Extremely burned Primary Feeds can result in a glowing Generator Light on the Dash which is caused by currrent flowing from the Alternator to the dash because the Dash voltage is lower than the Alternator voltage. Fuse Glow Submitted by T on Sat, 24/02/2007 - 12:19. If the particular car has a Fuse Panel that uses an Instrumentation Fuse, and it gets rusty, then the Alternator Light can be caused to glow when the Engine was running. Under this condition the Alternator Light would provide a reverse current flow from the Alternator in pollution models like HZ's, UC's and VB's and the Alternator Light could glow because the Anti-Dieselling Solenoid and Transmission Control Switch would provide a ground path for it in the absence of the system voltage at both ends of the Alternator Light. Models that don't use an Instrumentation Fuse won't do this because the red and pink wires are direct connected in the Ignition Switch giving both wires the same potential. T

Blowing Instrument Fuse:

The circle in the image shows the wire holder on Holden Engines. Engine movement can cause the insulation to be abraided from the wires. One wire supplies the throttle stop solenoid. If the wire shorts it will cause the instrument fuse to blow and the charge light to glow. Photo by Chopper75. Click to enlargen.


Any voltage drop across the Primary Feed is a direct cause of dim headlights and slow wipers. The effects of both a burned Alternator Feed and burned Primary Feed can unstabilise the electrical system and combine to produce very dim lights and very slow wipers, weak ignition, dim dash lights, dim tail lights, interior light. Indeed any load that connects to this wire. The top of the fuse board (particularly on HZ's and UC's) provide spade connections for additional primary feeds. Additional Primary Feed wires have one end connected to the large connector on the starter by a fusible link and each other end connected to one of the spade connectors on top of the fuse board. The additional current carrying ability will prevent the lights dimming and the wipers slowing down amongst other electrical loads that are fed from there. Additional Primary Feeds should be 30 amp cable fed by a 30 amp fusible link connected to the starter tap.

Fusible Link:

I use this Fusible Link  mentioned in Thread 1.  If the above links to Dick Smith are broken, the part number for an inline blade fuse holder is P7907, and a waterproof and screw mountable version of the blade fuse holder is part number P7909.

30 Amp Fusible Link. It uses a blade type fuse. See Thread 1. Image by Tonner Mike.
Starter Tap. Click to Enlargen. Image by MattsEHute.


Oxidised Starter Cables can cause problems that may appear to be inside the Starter. They include a Slow Cranking speed and the Starter Solenoid Clicking. Weak Electrics can also deteriorate the life of the Starter Ring Gear. This occurs because insufficient Electrical Supply will cause the Starter Pinion Gear to lose engagement whenever the Starter encounters Engine Compression. Pinion Gear cycling will seriously reduce the life of the Starter Ring Gear by ripping down the face of the Starter Ring Gear.



A High Capacity Battery is the best investment for long Battery life and minimum Electrical problems. Battery connections must be clean, tight and covered by Electrical Grease otherwise Starting and Charging problems are assured.
The image shows corrosion on the Battery terminals. This can produce slow cranking and poor charging problems. These should be cleaned and greased if those problems appear. Make Battery replacement a last resort if you want to avoid a needless expense and the problem recurring. Photo by Qute
Battery Terminals must be clean, tight and completely covered in Electrical Grease. If not, ions from within the Battery will be attracted to the Positive Terminal and erode it resulting in an Electrical Resistance there. The Resistance will prevent Alternator Charge Current getting in and Starter Current from getting out. See the Battery section for further info.


The Alternator must be able to carry the entire electrical load of the car plus have capacity in reserve for recharging the Battery after a start. Over the life of a car devices can be added which can exceed the Alternator's rating so it's important to measure this load and provide for it. A dash mounted Voltmeter is invaluable when it comes to monitoring the Alternator's performance. See the Alternator Alternator section for further info.


The Chassis of the Car is sometimes called "Earth" or "Ground". Leads that connect direct to the Chassis are called "Earth Leads" or "Ground Leads". There are 2 critical Earth Leads on an old Holden.


One is a cable of at least 200 amps rating that connects the Battery Negative to a bolt on the Engine's Cylinder Head (on 6 cyl engines). This is the Engine Block Ground cable. The other lead runs from the Battery Negative Terminal to the Car's Chassis and as standard is often only rated at about 50 amps. This is the Chassis Ground cable.  It is vital that both these leads have clean and tight connections since the absence of either of them can cause serious damage to the Car. If the 200 amp Engine Block Cable is missing or loose, the Starter Current will have to find a new return path to the Battery and will be only too happy to connect through every Gear and Bearing in the Gearbox as well as Universal Joints and Gears and Bearings in the Differential in addition to the Wheel Bearings at least until the Chassis Ground burns out. If the Chassis Ground is missing or loose, Electrical Loads in the car will travel from the chassis through the transmission and back to the Battery via the 200 amp lead. The Chassis Ground cable should carry a rating at least equal to the total Electrical Load of the car excluding the starter current. My cars carry 100 amp Chassis Ground cables. Needless to say in either case Gear Pitting can result. Some folks advise fitting a 3rd Ground Strap (of 200 amps current rating) that connects the cylinder head to the block. This lead prevents the Head Bolts and Head Gasket from carrying the high current passed by a Cranking Starter from the Block up to the Head which might cause any burning or corrosion there. As with the Alternator Feed and the Primary feed, these cables age through normal use, Engine Heat and any overloading they've been exposed to. If they look old and burned then replacing them can pay an Electrical Efficiency dividend and increase the brightness of dim lights and the speed of the wipers.

Tail Light Earths:

Corrosion and moisture can prevent the rear lights from working properly.

Tail Light Earths

Improved earthing in HR Tail Lights. Photo by Snowdownunder. Click to Enlargen.

The Charging System:

Think of the Charging System (whether it's an Alternator or a Generator) as being electrically the highest point in the system with all the current flowing down hill to Earth from there. If the Charging System Voltage isn't high enough, the current won't flow through the Car's Electrical System properly. If the cables (the veins and arteries) are blocked, then the current won't be able to get through either.
One way of minimising the load on the Dash FuseBoard is to establish an additional distribution point. Note that it's important to supply the items through a Fusible Link so that the wires will not start a fire in the event of a collision. Click to Enlargen. Photo by Qute.
The Charging System must be producing it's correct Voltage and that's the first check to make.
Note the undersized Earth Wire. Grey Motors have the main Engine Earth Wire on the Rear Engine Mount near the Starter. The green wire has since been uprated. Click to Enlargen. Photo by Sherro.
Red Wire - Primary Feed, Purple Wire - Starter Activation, Black Wire Battery +ve, Bare Copper - Starter +ve Brush. Photo by HRAmbo. Click to Enlargen.
Corrosion at the Battery Terminals caused an undesirable voltage drop within the Car. Photo by DadsHG. Click to Enlargen.

Red/Blue/Black Six Cylinder Engine Ground Bolt:

3/8" UNC .End of submission by myeh.Use a large Impact type Phillips Head Screwdriver to tighten or loosen.  


Thread 1

VB - VK Headlight Relay Conversion

Broken Primary Feed Thread 1Broken Primary Feed Thread 2


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