For all of you longtime SW readers, you will remember our '53 Buick Roadmaster 2-door hardtop. After finishing all phases of the restoration where it was ready for assembly, we drove it into the assembly shop, covered it and left it while we pursued buying other cars we wanted while they were affordable, ie: '51 Chevy 2 door Fleetline, '74 Mercedes 450 SLC, '67 Jaguar Mk 2 and a '92 Jaguar. We now are back on the '53 Buick and will resume our articles. Look for upcoming articles on starting the car after storage, checking the systems and assembly of chrome and interior. This month we are checking the electrical charging system.
In 1953, Buick changed from the 6 volt negative ground system to a 12 volt negative ground system on its 50 and 70 series, as many of the car makers were doing in the '50s. This had become necessary because of all the new power options, especially air conditioning which was becoming popular on many of the cars. The '53 Buick's system consists of the generator, regulator, charge indicator, battery, wires and cables, and ground. Its purpose is to restore to the battery the energy used in cranking the engine. It also supplies current to carry the electrical load to the ignition, lights and accessories at speeds over 25 mph up to the limit of the generator capacity. The charge indicator shows charging current going into the battery and the current leaving the battery, except when cranking the engine. The total charging rate of the generator is not indicated, since the current supplied by the generator to electrical units other than the battery doesnt pass through the indicator. The '53's generator is a two-brush type. The maximum generator output is controlled by the regulator. The generator is cooled by its pulley, which drives a fan that draws a draft of air through the generator, cooling it down.
The regulator is comprised of (1) cutout relay, (2) current regulator and (3) voltage regulator, all mounted on one base and enclosed by a cover. The above three are magnetic switches, whose function and operations are as follows: A. The cutout relay opens the circuit to prevent the battery from discharging to ground through the generator whenever the engine is stopped or the generator is operating at a low speed, producing a voltage less than the battery voltage. When the voltage of the generator is greater than battery voltage, the relay closes its circuit so that the generator can furnish current to the electrical system. B. The current regulator automatically controls the maximum output of the generator. When the electrical system demands are high, and the battery is low, the current regulator protects the generator from overload, by limiting its output to a safe value. C. The voltage regulator limits the voltage in the charging circuits to a safe value, controlling the charging rate of the generator with the requirements of the battery and the current-consuming electrical units in operation. Example: When the battery is low, the generator output is near maximum, but as the battery comes up to charge, the voltage regulator limits the voltage, reducing the generator's output, protecting the battery from over-charging.
A quick test for the system is to use a volt meter, putting the positive lead on the positive post of the battery and the negative lead on the negative post. Rev the engine to about 1100 RPMs. This will give a close reading, but a lower reading than a test at the voltage regulator--12.8 volts on this system. Never use this test right after charging the battery, because the battery voltage will be abnormally high for several hours.
First make sure that the battery is not less than 1.250 specific gravity. 1. Disconnect the wire from the generator regulator marked battand connect an ammeter in series with its terminal and the disconnected wire. 2. Then connect a jumper wire between the regulator terminal marked F and the base plate of the regulator, so that current and voltage regulator can not operate to control generator output. 3. Start engine with all electrics turned off, slowly increase engine speed until ammeter registers 30 amperes, about 1100 RPMs with generator hot (never exceed 1300 RPMs while "F" terminal is grounded. 4. If 30 amperes can not be reached, the generator does not have proper output.
After above test, we polarized the generator by removing the test ammeter and jumper wire from F terminal and base, then, before starting the engine, momentarily touched a wire between batt and gen terminals of regulator with fan belt loose. This allowed the generator to motor.
VOLTAGE REGULATOR TESTING:
Leaving all wires attached, and using a volt meter, place the positive lead on the battpole of the voltage regulator, and ground the negative lead to the car. Rev the engine to about 1100 RPMs. Using this test, the reading should be 14.5 volts. To adjust the regulators output, remove the cover and adjust the field contacts.
On OEM regulators, turn the screw on the field clockwise to increase voltage, and counterclockwise to decrease. Some replacement units don't have adjustment screws, and require bending the contacts to change the voltage, bringing them closer to increase, and vice versa. The voltage output will decrease when you put the cover back on, so a final test must be done with the cover on, and the engine at about 1100 RPMs. The voltage should be 14.5 and not exceed 15 volts.
It is easy to burn up a regulator or generator by even momentarily touching the wrong wires. These tests are the ones we performed on our '53 Buick. Always check your motors manual to see what kind of system you have, ie: negative ground, positive ground, 3rd brush generator, etc. And remember to polarize the generator after any wires or components have been removed from the system. See you next month. Keep 'em driving!