The voltage regulators that are used with alternators are transistorized and cannot be serviced. If the voltage regulator is not operating properly, it must be replaced.
The voltage regulators that are used with shunt type generators are serviceable and can be adjusted. These regulators have three units: the circuit breaker, the voltage regulator and the current limiting regulator. Each performs a separate function.
The function of the voltage regulator unit is to hold the generated voltage at a predetermined value as long as the circuit values allow the voltage to build to the operating load.
The electromagnet of the voltage regulator unit has a winding of many turns of fine wire and is connected across the charging circuit so that the system voltage controls the amount of magnetism. The contacts of the voltage regulator unit are connected in the generator field circuit so that the field circuit is completed through the contacts when they are closed and through a resistor when the contacts are opened.
When the voltage rises to a predetermined amount, there is sufficient magnetism created by the regulator winding to pull the armature down. This opens the contacts and inserts resistance in the field circuit of the generator, thus reducing the field current. The generated voltage immediately drops, reducing the pull on the armature to the point where the spring closes the contacts. The output again rises and the cycle is repeated.
These cycles occur at sufficiently high frequencies to hold the generated voltage at a constant level and they will continue as long as the voltage of the circuit is high enough to keep the voltage regulator unit in operation. When there is a current load that is great enough to lower the battery voltage below the operating voltage of the voltage regulating unit, the contacts will remain closed and the generator will maintain a charging rate that is limited by its speed and capacity output.
CURRENT LIMITING REGULATOR
The function of the current limiting regulator is to limit the output of the generator to its maximum safe output.
The electromagnet of the current regulator unit consists of a winding of heavy wire connected in a series with the generator output. When the generator output reaches a predetermined level, the current in the winding produces enough magnetism to overcome spring tension and pull the armature down. This opens the contacts and inserts resistance in the field circuit of the generator. With the field current reduced by the resistance, the generator output falls and there is no longer sufficient magnetism to hold the contacts open. As soon as the spring closes the contacts, the output and the cycle is repeated. These cycles occur at a high enough frequency to limit the output to a minimum fluctuation.
VOLTAGE TESTS & ADJUSTMENTS
The circuit breaker is the unit with the heavy wire windings and is located on the end of the unit.
- Connect an ammeter in series with the regulator B (battery) terminal and the lead that is removed from that terminal. Connect a voltmeter from the regulator A (armature) terminal to the regulator base.
- Disconnect the field lead from the regulator F terminal and insert a variable resistance between the lead and the regulator terminal.
- Run the generator at about 1000 rpm. Insert all of the resistance in the field circuit. Slowly reduce the resistance, noting the voltage reading just before the change caused by the closing of the circuit breaker. Increase the charging rate to the figure specified for the regulator being tested, then reduce the charging rate by inserting resistance into the field circuit. Note the charging rate just before the circuit breaker opens and the ammeter reading drops to 0. The closing voltage and the opening voltage or current should be within the limits specified.
- To adjust the closing voltage, change the armature spring tension by bending the hanger at the lower end of the spring. Increase the spring tension to raise the closing voltage or decrease the tension to lower the voltage. To adjust the opening voltage, raise or lower the stationary contact, keeping the contacts perfectly aligned. Increasing the contact gap lowers the opening voltage. Change the contact gap by expanding or contracting the contact gap by expanding or contracting the stationary contact bracket, keeping the contacts aligned. Do not adjust the gap between the contacts to less than the specified minimum.
The voltage regulator unit is the one with the fine wire winding.
- Connect the ammeter as noted in the previous procedure and connect the voltmeter between regulator B terminal and the regulator base. Remove the variable resistance from the field circuit.
- Run the generator at 1 / 2 maximum output for 15 minutes to make sure the regulator is at normal operating temperature. Have the cover on the unit during this warm up period and also when taking the readings.
- Stop the engine, then bring it to approximately 2,500 generator rpm. Adjust the amperage to one half of the maximum output by turning on lights or accessories and then note the voltmeter reading. This reading should be within the limits specified for the voltage regulator.
- To adjust the operating voltage, change the armature spring tension by bending the hanger at the lower end of the armature spring. After each adjustment, stop the engine and then restart it. Bring it up to speed and adjust the current before taking a reading. The clicks of the opening and closing of the contacts should be regular and clear without irregularities. If the tone is not clear and regular, remove the regulator cover and inspect the contacts. The contacts should be flat and not burned excessively, and should be aligned to make full face contact. Refer to the section on cleaning the contacts if necessary.
The current regulator is the unit in the middle of the unit with the heavy wire winding.
- Connect the regulator and instruments as described in the previous procedures for the voltage regulator and run the generator at approximately 3,000 generator rpm. Turn on lights and accessories so the generator must charge at its maximum rate. The ammeter should show a reading within the specified limits.
- To adjust the opening amperage, change the armature spring tension by bending the hanger at the lower end of the armature spring. Stop the engine after each adjustment and then restart it. Bring the engine to speed and take an ammeter reading. Keep the cover on the unit when taking the readings. The clocks of the points closing and opening should be clear in tone and regular in frequency without irregularities or misses. If this is not the case, the contacts will have to be serviced.
The contacts should be inspected on all three of the units inside the cover of the voltage regulator. The contacts will become grayed and slightly worn during normal use. If the contacts are burned or dirty, or if they are not smooth or aligned properly, they should be adjusted and cleaned. File the contacts smooth. Just file enough so that there is a smooth surface presented to each contact. It is not necessary to file out every trace of pitting. After filing, dampen a clean cloth with carbon tetrachloride and pull the cloth between the contacts of each of the three units. Repeat with a clean dry cloth.
Keep in mind that after filing the points, the gap might have been changed enough to affect the performance of the three units. Check the three units and perform the adjustments. It might be a good idea to examine the contacts before making any adjustments. If the contacts need to be serviced, do it before adjusting spring tensions, etc.
REMOVAL & INSTALLATION
If the voltage regulator still does not function properly, after all of the checks and adjustments, replace the entire unit as described in the following procedure:
- Remove all of the electrical connections. Label them as you remove them so you can replace them in the correct order on the replacement unit.
- Remove all of the hold-down screws and then remove the unit from the vehicle.
- Install the new voltage regulator using the hold-down screws from the old one, or new ones if they are provided with the replacement regulator. Tighten down the hold-down screws.
- Connect the armature lead to the armature terminal of the voltage regulator.
- Connect the battery lead to the battery terminal of the voltage regulator.
- Momentarily touch the field lead to the battery terminal of the voltage regulator. This polarizes the generator and voltage regulator so they have the same polarization as the rest of the electrical system. This has to be done every time all of the leads are disconnected from the generator voltage regulator.
- Connect the field lead to the field terminal of the voltage regulator.