Toyota Celica 1986-1993 Repair Guide



The alternator converts the mechanical energy supplied by the drive belt into electrical energy by a process of electromagnetic induction. When the ignition switch is turned on, current flows from the battery through the charging system light (or ammeter) to the voltage regulator, and finally to the alternator. When the engine is started, the drive belt turns the rotating field (rotor) in the stationary windings (stator), inducing alternating current. This alternating current is converted into usable direct current by the diode rectifier. Most of this current is used to charge the battery and to supply power for the vehicle's electrical accessories. A small part of this current is returned to the field windings of the alternator enabling it to increase its power output. When the current in the field windings reaches a predetermined level, the voltage regulator grounds the circuit preventing any further increase. The cycle is continued so that the voltage supply remains constant.

All models use a 12 volt alternator. All models have a transistorized, nonadjustable regulator, integral with the alternator.


To prevent damage to the alternator and regulator, the following precautionary measures must be taken when working with the electrical system.

  1. NEVER reverse the battery connections. Always check the battery polarity visually. This is to be done before any connections are made to ensure that all of the connections correspond to the battery ground polarity of the car.
  3. Booster batteries must be connected properly. Make sure the positive cable of the booster battery is connected to the positive terminal of the battery which is getting the boost.
  5. Disconnect the battery cables before using a fast charger; the charger has a tendency to force current through the diodes in the opposite direction for which they were designed.
  7. NEVER use a fast charger as a booster for starting the car.
  9. NEVER disconnect the voltage regulator while the engine is running, unless as noted for testing purposes.
  11. Do NOT ground the alternator output terminal.
  13. Do NOT operate the alternator on an open circuit with the field energized.
  15. Do NOT attempt to polarize the alternator.
  17. Disconnect the battery cables and remove the alternator before using an electric arc welder on the car.
  19. Protect the alternator from excessive moisture. If the engine is to be steam cleaned, cover or remove the alternator.


There are several checks that can be done with inexpensive equipment. The first thing to do is to see if the discharge warning light on the dashboard lights when the ignition switch is turned on. If it is not lit, check for blown fuses, a blown out bulb itself (The system will not charge with a bad bulb) or bad connections.

If the warning light does light with the ignition switch on, but stays on with the engine running, check for a loose (or missing) belt, a loose or faulty battery cable, corrosion, a blown fuse or fusible link or a shorted or open wire.

If everything seems to be good (including the battery), but the charge light is always on, then the alternator itself probably is to blame. This does not mean the whole alternator needs to be replaced. Many times, the IC regulator can become faulty and cause the no-charge condition. There is a way to determine whether just the IC regulator or the whole alternator should be replaced.

The alternator can be "full-fielded;" that is, the F terminal can be shorted to ground, making the alternator think there is a heavy load on the electrical system. If the alternator starts putting out when the F terminal is shorted to ground, then the IC regulator is probably faulty. If the alternator still does not put out when the F terminal is grounded, then the whole alternator should probably be replaced. It can be concluded that the alternator is "putting out" by observing the voltage of the battery. The system is charging when the battery voltage is approximately 14-15 volts. If it is only 12-12.5 volts, something is wrong. If the charging voltage is too high (more than 15 volts, the battery smells like sulfur or frequently runs out of water or the bulbs in the vehicle burn out too frequently, then the IC regulator is probably faulty (See Regulator).

Check the alternator and IC regulator by performing the following:

  1. Ground the F terminal on the alternator.
  3. Start the engine.
  5. Analyze the voltage, using the information above.

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Fig. Fig. 1 Checking the alternator and IC regulator2S-E, 3S-FE and 3S-GE engines shown

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Fig. Fig. 2 Checking the alternator and IC regulator4A-FE, 5S-FE and 3S-GTE engines shown


On models with an air bag, wait at least 30 seconds from the time that the ignition switch is turned to the lock position and the battery is disconnected before performing any further work.

  1. Disconnect the negative battery cable.
  3. Remove the alternator pivot bolt or loosen the belt adjustor bolt. Remove the drive belt from the alternator pulley.
  5. Pull back the rubber boots and disconnect the wiring from the back of the alternator. Some wiring may be held either by nuts and bolts or by connectors with locking tabs; disconnect them carefully.

Before removing the alternator, check for any wires or hoses which may interfere or be damaged as the alternator comes out. Move or disconnect lines before they become a problem.

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Fig. Fig. 3 Disconnecting the alternator power wire5S-FE engine shown

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Fig. Fig. 4 Disconnecting the alternator connector5S-FE engine shown

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Fig. Fig. 5 Removing the alternator5S-FE engine shown

  1. Remove the alternator mounting bolt(s) and then withdraw the alternator from its bracket. The alternator is heavier than it appears; use two hands.

To install:

  1. Installation is in the reverse order of removal; place the alternator in position, install and secure the bolts and connect the wiring. Install and adjust the belt and final tighten the mounting hardware. Check for unusual noises or for any belt interference.

If the battery became discharged due to a fault in the charging system, make sure to have the battery recharged before starting the vehicle. Do NOT make it the alternator's job to recharge the battery, since alternator overheating can result.