Take a look at your shorts
You know, I really hate to see a grown man cry, especially one that should be happy with a nice old LaSalle or Cadillac.
One type of problem that seems to bring a lot of tears (and fears) is electrical problems. It never ceases to amaze me that many old car hobbyists who have trouble telling the difference between an end-wrench and a socket are not afraid to tackle a backyard engine teardown and overhaul.
Even some experienced mechanics are afraid to change a light bulb or even touch any part of the electrical system.
I feel the same way about “modern iron” with all the computers, chips, circuit boards, etc. It seems that when the carmakers went to 12-volt systems, they began to make electrical systems more complicated. But when it comes to the old 6-volt systems, it’s really a piece of cake if you use a little horse sense and logic.
A big help is to understand a few basic circuits and their functions. The six basic circuits are battery, charging, starting, ignition, lighting and accessory. Let’s talk a little about each one.
The heart and start of the system is the battery– very simple, it’s good or it’s bad. It is a positive or a negative terminal that hooks to two cables. One is a power cable and one is a ground cable. This can be the start of many problems that are easy to correct.
First of all, you will have a positive or negative ground, and many of our old Cads and LaSalles are positive ground. They are not interchangeable anywhere in the electrical system. Make sure you have heavy enough cables. A minimum for 6-volt systems is OO gauge cables. The power cable generally goes to the starter and all the rest of the circuits come from this point. The ground cable usually goes to the frame.
Many electrical problems can be traced to loose or dirty connections from the battery to these two points. You must also have a good heavy ground cable or strap to the engine block and the body. If you forget everything else, remember the rule: 90 percent of all electrical problems are because of a poor ground somewhere.
Anything electrical must have a good ground to work properly. To have a good ground anywhere, you must start with a good main ground.
The next circuit is the charging circuit, which consists of a generator that replaces electricity to the battery and powers all the circuits in the car (except the starter) when the car is running.
The regulator governs the amount of voltage and amperage flowing from the generator to the battery and other elements using current. Kind of a traffic cop directing electrical flow—if they work in harmony, it supplies enough current to operate everything in use and a bit left over to charge the battery. When the battery is at full charge, it lets the generator back off and produce only what is needed.
If any one of these three items (battery, generator or regulator) go bad, they can damage one or both of the others. When replacing or repairing any of the three, always polarize. Your service manual will explain this simple procedure.
The starter circuit has only one job, which is to turn over the engine enough to start the car. When you push the starter button, you activate a relay that provides a heavy enough current to pull a solenoid that does two things at once. First of all, it engages the starter to the flywheel. Second, it supplies heavy current to the starter motor, causing it to turn over.
When the engine starts, the Bendix drive disengages the starter from the flywheel. Also at this time, the regulator and generator cut off the power to the relay. If all the systems are working right, the starter relay will not engage when the generator is charging.
The ignition circuit is actually two separate circuits working in harmony. One is low voltage (6 volts), one is high voltage (10,000 or more volts). The purpose is simple. You take 6 volts from the batter (or generator) and convert it to voltage sufficient to make a spark at each spark plug at the right time. Here you have three elements working in harmony—the distributor, the coil and the plugs.
The spark plugs with the right gap, being clean and not broken are simple…“’nuff said.”
The distributor and coil work closer together. The low voltage goes directly into the coil and out to the distributor looking for a ground. It gets a ground when the points close and sets up a magnetic field. When the points open, this magnetic field collapses, it in turn generates a high voltage current that goes from the center of the coil to the center of the distributor cap, down to the rotor which will be next to one of the spark plug wires, to the top of the spark plug and makes a spark while going to ground.
This needs to be timed to the precise instant that the piston is a few degrees before top dead center. At 2,000 rpm (or about 50 mph) this happens 8,000 times a minute or about 133 times per second. This obviously requires precise timing and a clean sparkless opening of the points.
The purpose of the condenser is to divert the low voltage long enough to prevent the points from sparking.
The lighting circuit and accessory circuit are very much intermingled and similar in operation. The main brain and traffic cop for these are the light switch and ignition switch. The light switch has power all the time, but will only pass current to certain places and only when the switch is in a certain position. Also certain lights and accessories will only get power when the ignition switch is on. Both switches work together to decide what works when.
The light switch usually has a circuit breaker that opens under too much load (heat) and most accessories will have a separate fuse. Two of the dash instruments, the gas gauge and temperature gauge, operate on the same principle in that both have power all the time and the float in the gas tank as well as the heat sending unit regulate the amount of ground allowed.
When these older cars are restored in a professional manner, many parts are cleaned and painted individually and then reassembled. Care must be taken that good grounds are provided for. Rust can also prevent a good ground. All light assemblies, the gas tank and the dash should have separate specific ground wires installed in an unobtrusive manner.
Make sure all accessories have a good ground. Remember, I told you earlier, about 90 percent of problems are from poor grounds.
When any circuit doesn’t have a good ground, it will look for one through another or adjacent circuit. This creates many ghosts and gremlins.
For example, you step on the brake and the dash lights come on. Maybe your turn on the radio and the heater starts to run, or maybe you put on the turn signal and the horn blows. It can boggle the imagination when these ghosts and gremlins play their games. I will say again—the first thing to look for in an electrical problem is a bad ground.
Of course, when you have a ground that you don’t want, it is called a short. Usually a short occurs when old wires lose their insulation and touch each other. This also happens when a power line rubs off some insulation and grounds out or “shorts out.” These are dangerous and cannot only burn up the wiring, but complete units or the whole car.
If you are restoring one of these fine old cars or driving as is, the first thing to do is install a new wiring loom. Don’t take a chance–or to put it more factually–“Don’t take it in the shorts.”
See you next month.