See Figures 1 and 2
Three types of voltage regulators have been used in the Corvette since 1963. The first type of regulator, hereafter referred to as Type One, is a double-contact model which is mounted externally, separately from the alternator. The Type One regulator was used on most 1963-68 and some 1969 Corvettes. This regulator is housed in a basically square black metal case and has four electrical terminals.
The second type of regulator, hereafter called Type Two, is a transistorized model which was offered as an option with the transistorized ignition system in 1965. The Type Two regulator is externally mounted and uses: a) one transistor which assists in limiting the voltage to a preset value, and b) two diodes which protect the system from transient voltage which may occur. The Type Two regulator is easily identified by the finned regulator casing.
The third type of regulator, hereafter called Type Three, is mounted inside of the Delcotron alternator. This electronic regulator, used in some 1969 and all later Corvettes, is nonadjustable and must be replaced if defective.
REMOVAL & INSTALLATION - Types One and Two
- Disconnect the negative battery cable at the battery.
- Disconnect the wiring harness from the regulator.
- Remove the regulator mounting screws and remove the regulator.
- Installation is the reverse of the previous steps. Be sure that the regulator base is properly grounded and do not overtighten the mounting screws, as this will cancel the cushioning effect of the rubber grommets.
- Remove the alternator from the vehicle as previously outlined.
- Scribe a line on the alternator case from front-to-rear which will aid in attaining the proper relationships between components during assembly.
- Remove the four through-bolts which join the end frame assemblies.
- Separate the end frames by carefully prying between the drive (front) end frame and the stator. DO NOT pry between the slip ring (rear) end frame and the stator. The stator is wired to the rectifier bridge which is attached within the rear end frame.
- Disconnect the three stator wire terminals at the rectifier bridge connections.
- Remove the stator from the slip ring end frame. It may be necessary to carefully pry the stator from the frame.
- Remove the three screws which retain the brush holder and regulator. Note the positions of the two screws which are equipped with plastic insulating washers-these screws MUST be installed in their original locations.
Some alternators also have a resistor which is installed between the regulator and brush ground terminals. Note its position and reinstall it in the same manner.
- Lift the brush holder and regulator out of the alternator frame.
- The regulator is installed in the reverse of the previous steps. Before installing the brush holder, push the brushes into the holder and insert a straightened paper clip through the holes provided in the holder for brush retention. Remove the paper clip after the alternator is assembled.
VOLTAGE ADJUSTMENT - Types One and Two Only
See Figure 3
The adjustment procedure is the same for both types of regulators, except for the locations where the adjustment is made. On the Type One regulator, the adjustment screw is under the regulator cover; the Type Two regulator is adjusted externally after removing the allen screw from the adjustment screw access hole.
- Insert a 1 / 4 ohm-25 watt fixed resistor into the charging circuit at the horn relay junction block, as shown in the accompanying illustration.
- Install a voltmeter as shown in the accompanying illustration.
- Warm the engine by running it for about fifteen minutes at 1,500 rpm or more.
- Disconnect the regulator connector and reconnect it to cycle the regulator.
- Read the voltage on the voltmeter. If the voltage reading is 13.5-15.2 volts, the regulator does not need adjustment or replacement. If the voltage is not within these limits, leave the engine running at 1,500 rpm and proceed to step 6.
- On Type One regulators, disconnect the regulator connector and remove the regulator cover. Reconnect the regulator connector. On Type Two regulators, remove the adjustment screw access plug from the regulator case (the plug is actually an allen screw).
- Observe the voltmeter reading and turn the voltage adjustment screw until the voltmeter reads 14.2-14.6 volts.
- On Type One regulators, disconnect the regulator connector, install the cover and reconnect the regulator connector.
- Continue running the engine at 1,500 rpm to re-establish the internal temperature of the regulator (Type One only).
- Again, cycle the regulator by disconnecting and reconnecting the regulator connector.
- Recheck the voltmeter reading: If it is between 13.5 and 15.2 volts, the regulator is good; if not, replace the regulator.
- On Type Two regulators, If the voltmeter reading is okay, reinstall the access hole plug.
VOLTAGE TESTING - Type Three Regulator Only
Though other tests of the internal voltage regulator exist, the following test is quite accurate and requires a minimum of tools.
The following test must be performed with the engine at normal operating temperature.
- Attach one lead of a voltmeter to the "BAT" terminal of the alternator and the other lead to a good ground.
- Start the engine and operate at about 1,500 rpm.
- Observe the voltmeter reading: If it is approximately 13.5-15.2 volts, the regulator is properly limiting the voltage to the battery. If the voltage is above about 15.2 volts, replace the voltage regulator as previously described. If the voltage is below 13 volts, locate the test hole in the rear end frame of the alternator (refer to the illustration under Alternator Tests.) Insert a screwdriver into the test hole about 3 / 4 " to depress the field grounding tab. Under no circumstances should you push the screwdriver further than 1" into the alternator. If the voltage reading increases as the screwdriver is put into the test hole, the alternator is functioning properly and the regulator must be replaced. If the voltage reading did not increase with the insertion of the screwdriver, the alternator must be disassembled and tested.
If the test hole is not accessible, remove the alternator and test the following components: rotor, stator, rectifier bridge, diode trio, and brushes (1/4" minimum length). Replace any component which may be defective. If these components are okay, replace the voltage regulator.OFF VEHICLE TEST
See Figures 5 and 6
This test requires the use of a fast charger.
- Remove the voltage regulator from the alternator.
- Connect voltmeter and fast charger to battery as shown.
- Connect regulator and test light as shown, observing battery polarity.
- The test light should be on when connected.
- Turn on the fast charger and slowly increase the charge rate. Check the voltmeter and make sure that the test light goes out at a minimum of 13.5 volts, and a maximum of 16.0 volts.