How to Keep the Smoke Inside the Wires, or Why do the English Drink Warm Beer?
...they all have Lucas refrigerators!!!
By Jim Leach
The first time I heard the Lucas puns I chuckled too, but most of the stories of the "Prince of Darkness" are unwarranted. I have worked on dozens of Lucas equipped cars and you might be surprised at the real reason for most of the electrical system problems. The following is neither typical nor exaggerated; it is a classic and true example of what I have found trying to keep the electrical "circulatory systems" of English cars healthy.
In Portland, Oregon I bought a 1961 Hillman Husky whose prior owner was a member of the J.C. Whitney "add-a-useless-device-of-the-month-club". Stuffed between the grill and the radiator was a klaxon (submarine diving alarm). Under the dashboard, a battery inverter (to change + ground to - ground) and an intricate alarm system added a couple of dozen wires running in all directions, and a fancy stereo with amplifier and graphic equalizer added to the birds nest of wiring. Two sets of speaker wires from prior installations remained, as did some of their power wires. Wiring had been routed for fog or driving lights and all of this was crammed up under the dashboard, and every device was wired directly to the ignition switch. Absolutely nothing electrical in the car worked.
To restore the electrical system I removed all of the junk that had been added, including three pairs of sharp-edged metal brackets (better suited for fence repair) that in years past may have mounted 8-track tape players, and I simply returned the original wiring to stock. The small contacts in the ignition switch had been severely overloaded and destroyed when they were forced to carry many times the current for which they were designed. The electrical problems were caused by the parasitic additions to the original wiring harness, or by the "golden tooled" person that incorrectly installed them, and are not representative of "lousy-Lucas-electrics"...but Lucas traditionally gets the blame. I replaced the ignition switch and everything works. The Husky wiring harness was in fairly good condition under the dashboard. My Tiger, on the other hand...every other wire was brown...the workmanship of another genius.
Adding Unswitched Accessories
(Devices independent of the ignition switch) Create new fused circuits originating from the battery side of the starter solenoid. This is a convenient junction and is electrically equivalent to the "hot" battery terminal itself. (Note: All devices so installed, are isolated from the factory wiring harness and will not register on the ammeter) Example: Electric radiator cooling fan An Electric Fan should be able to continue to cool the radiator with the engine stopped (ignition key removed). It should have its own thermostatically controlled on/off switch. Example: 12 volt power outlet (same as a lighter socket) If you want to be able to run your 12 volt coffee pot or an air compressor at the autocross track, you need to have a power outlet capable of handling a large amount of current. The accessory terminal contacts on the ignition key were not meant to handle the current it takes to brew coffee. This is not an example of "lousy-Lucas-electrics" but of design parameters. By the way, I have a 12 volt RV coffee pot I use in my Tiger and Minx on cold foggy mornings at the race track!
Adding Key-Switched Accessories
Devices switched on and off by the ignition switch. For example, an Am-Fm Stereo receiver. It is usually desirable to connect a radio so it automatically shuts off when the ignition key is removed from the switch. This insures the device cannot drain the battery after you leave the car.
On most Lucas ignition switches, the accessory contact is terminal #4. Always check the wiring diagram before adding any fused accessories. Example: 12 volt power outlet (same as a lighter socket) .
If you want to use a radar/lidar detector or other device that draws minimal current, you may want to install a switched power outlet. As above, the power outlet and device connected to it will not be accidentally left 'on' when you leave the car. (Note: All devices so installed become part of the factory wiring harness and will register on the ammeter)
Relay Switching Of Accessories
The starter motor on most cars is relay-switched. It is more practical to use a small wire connected to the ignition switch to energize the starter solenoid (a relay), and have it handle the large current requirements of the starter motor. The same theory applies to some automotive accessories such as high power or multiple driving lights.
Depending on the accessory, the relay may be connected either directly to the ignition switch as a switched accessory or to a dashboard or console mounted switch, or to both. This technique has advantages over direct wiring of accessories: the control wires from the switch to the relay can be small gauge; their length is not a concern; and the switch handles only the current required to energize the relay. The large capacity wiring that actually handles the load can be routed directly to the accessory, and can be kept shorter resulting in less resistance and/or loss.
Keep in mind, Lucas charging systems were designed to maintain the charge of the battery with the standard ancillaries operating (heater blower motor, windshield wiper motor, etc.) and there is little surplus current generated to cover the requirements of rally lights, sub-woofer blaster stereo systems and the like. In this case, the charging system is something like a garden hose. One hose can water a pretty good sized garden, but if you connected this hose to a sprinkler system at a golf course, there wouldn't be enough water to do the job. The charging system could operate perfectly and in a short time you could still end up with a very low battery.
Voltmeter vs. Ammeter - A Simple Comparison
The Voltmeter: A voltmeter is a device that samples the pressure of electrical potential, present in a circuit, at a given instant. The pressure is called voltage or electro-motive-force. A voltmeter has a high impedance or internal resistance and is always wired in parallel, in relation to the components of a circuit. The usage of a voltmeter is similar to sampling the air pressure in a tire with a pressure gauge. It is accomplished from outside the circuit (or tire!). The electric water temperature gauge and fuel gauge are both examples of voltmeters.
The Ammeter: An ammeter is a device that registers the "current affairs" occurring within a circuit: it measures the rate of electron current flow, at a given instant. It samples the number of electrons, in coulombs per second flowing through it. The rate of flow is expressed in units called amperes. One coulomb is equivalent to about 6 billion-billion electrons-per-second past a fixed point in a conductor. (6.25 X 1018 electrons per second). This is a measurement of quantity over time. An ammeter adds no significant resistance to a circuit and it consumes no energy: it is always wired in series with the components of a circuit.
By Jim Leach
The first time I heard the Lucas puns I chuckled too, but most of the stories of the "Prince of Darkness" are unwarranted. I have worked on dozens of Lucas equipped cars and you might be surprised at the real reason for most of the electrical system problems. The following is neither typical nor exaggerated; it is a classic and true example of what I have found trying to keep the electrical "circulatory systems" of English cars healthy.
In Portland, Oregon I bought a 1961 Hillman Husky whose prior owner was a member of the J.C. Whitney "add-a-useless-device-of-the-month-club". Stuffed between the grill and the radiator was a klaxon (submarine diving alarm). Under the dashboard, a battery inverter (to change + ground to - ground) and an intricate alarm system added a couple of dozen wires running in all directions, and a fancy stereo with amplifier and graphic equalizer added to the birds nest of wiring. Two sets of speaker wires from prior installations remained, as did some of their power wires. Wiring had been routed for fog or driving lights and all of this was crammed up under the dashboard, and every device was wired directly to the ignition switch. Absolutely nothing electrical in the car worked.
To restore the electrical system I removed all of the junk that had been added, including three pairs of sharp-edged metal brackets (better suited for fence repair) that in years past may have mounted 8-track tape players, and I simply returned the original wiring to stock. The small contacts in the ignition switch had been severely overloaded and destroyed when they were forced to carry many times the current for which they were designed. The electrical problems were caused by the parasitic additions to the original wiring harness, or by the "golden tooled" person that incorrectly installed them, and are not representative of "lousy-Lucas-electrics"...but Lucas traditionally gets the blame. I replaced the ignition switch and everything works. The Husky wiring harness was in fairly good condition under the dashboard. My Tiger, on the other hand...every other wire was brown...the workmanship of another genius.
Adding Unswitched Accessories
(Devices independent of the ignition switch) Create new fused circuits originating from the battery side of the starter solenoid. This is a convenient junction and is electrically equivalent to the "hot" battery terminal itself. (Note: All devices so installed, are isolated from the factory wiring harness and will not register on the ammeter) Example: Electric radiator cooling fan An Electric Fan should be able to continue to cool the radiator with the engine stopped (ignition key removed). It should have its own thermostatically controlled on/off switch. Example: 12 volt power outlet (same as a lighter socket) If you want to be able to run your 12 volt coffee pot or an air compressor at the autocross track, you need to have a power outlet capable of handling a large amount of current. The accessory terminal contacts on the ignition key were not meant to handle the current it takes to brew coffee. This is not an example of "lousy-Lucas-electrics" but of design parameters. By the way, I have a 12 volt RV coffee pot I use in my Tiger and Minx on cold foggy mornings at the race track!
Adding Key-Switched Accessories
Devices switched on and off by the ignition switch. For example, an Am-Fm Stereo receiver. It is usually desirable to connect a radio so it automatically shuts off when the ignition key is removed from the switch. This insures the device cannot drain the battery after you leave the car.
On most Lucas ignition switches, the accessory contact is terminal #4. Always check the wiring diagram before adding any fused accessories. Example: 12 volt power outlet (same as a lighter socket) .
If you want to use a radar/lidar detector or other device that draws minimal current, you may want to install a switched power outlet. As above, the power outlet and device connected to it will not be accidentally left 'on' when you leave the car. (Note: All devices so installed become part of the factory wiring harness and will register on the ammeter)
Relay Switching Of Accessories
The starter motor on most cars is relay-switched. It is more practical to use a small wire connected to the ignition switch to energize the starter solenoid (a relay), and have it handle the large current requirements of the starter motor. The same theory applies to some automotive accessories such as high power or multiple driving lights.
Depending on the accessory, the relay may be connected either directly to the ignition switch as a switched accessory or to a dashboard or console mounted switch, or to both. This technique has advantages over direct wiring of accessories: the control wires from the switch to the relay can be small gauge; their length is not a concern; and the switch handles only the current required to energize the relay. The large capacity wiring that actually handles the load can be routed directly to the accessory, and can be kept shorter resulting in less resistance and/or loss.
Keep in mind, Lucas charging systems were designed to maintain the charge of the battery with the standard ancillaries operating (heater blower motor, windshield wiper motor, etc.) and there is little surplus current generated to cover the requirements of rally lights, sub-woofer blaster stereo systems and the like. In this case, the charging system is something like a garden hose. One hose can water a pretty good sized garden, but if you connected this hose to a sprinkler system at a golf course, there wouldn't be enough water to do the job. The charging system could operate perfectly and in a short time you could still end up with a very low battery.
Voltmeter vs. Ammeter - A Simple Comparison
The Voltmeter: A voltmeter is a device that samples the pressure of electrical potential, present in a circuit, at a given instant. The pressure is called voltage or electro-motive-force. A voltmeter has a high impedance or internal resistance and is always wired in parallel, in relation to the components of a circuit. The usage of a voltmeter is similar to sampling the air pressure in a tire with a pressure gauge. It is accomplished from outside the circuit (or tire!). The electric water temperature gauge and fuel gauge are both examples of voltmeters.
The Ammeter: An ammeter is a device that registers the "current affairs" occurring within a circuit: it measures the rate of electron current flow, at a given instant. It samples the number of electrons, in coulombs per second flowing through it. The rate of flow is expressed in units called amperes. One coulomb is equivalent to about 6 billion-billion electrons-per-second past a fixed point in a conductor. (6.25 X 1018 electrons per second). This is a measurement of quantity over time. An ammeter adds no significant resistance to a circuit and it consumes no energy: it is always wired in series with the components of a circuit.
