DESCRIPTION
Alternators are conventional 3-phase, self-rectifying type units containing 6 diodes (3 positive and 3 negative) which are used to rectify current. (Scheme 1) An internally-mounted, Integrated Circuit (IC) regulator is used on all models.
Scheme 1
BELT DEFLECTION
Measure belt deflection in center of longest pulley-to-pulley span. See BELT DEFLECTION SPECIFICATIONS table. If belt deflection is not as specified, adjust as necessary.
| Application | Deflection - In. (mm) | ||
|---|---|---|---|
| B2200 | |||
| New Belt | 0.28-0.31 (7.0-8.0) | ||
| Used Belt | 0.31-0.35 (8.0-9.0) | ||
| B2600i | |||
| New Belt | 0.39-0.47 (10.0-12.0) | ||
| Used Belt | 0.43-0.51 (11.0-13.0) | ||
| Miata | |||
| New Belt | 0.31-0.35 (8.0-9.0) | ||
| Used Belt | 0.35-0.39 (9.0-10.0) | ||
| MPV | |||
| 4-Cylinder Engine | |||
| New Belt | 0.39-0.47 (10-12) | ||
| Used Belt | 0.43-0.57 (11-13) | ||
| V6 Engine | |||
| New Belt | 0.35-0.39 (9-10) | ||
| Used Belt | 0.39-0.47 (10-12) | ||
| MX-3 | |||
| 4-Cylinder Engine | |||
| New Belt | 0.31-0.35 (8.0-9.0) | ||
| Used Belt | 0.35-0.39 (9.0-10.0) | ||
| V6 Engine | |||
| New Belt | 0.24-0.28 (6.0-7.0) | ||
| Used Belt | 0.28-0.31 (7.0-8.0) | ||
| MX-6 & 626 | |||
| New Belt | 0.24-0.31 (6.0-8.0) | ||
| Used Belt | 0.28-0.35 (7.0-9.0) | ||
| Protege & 323 | |||
| New Belt | 0.31-0.35 (8.0-9.0) | ||
| Used Belt | 0.35-0.39 (9.0-10.0) | ||
| RX7 | |||
| New Belt | 0.47-0.59 (12.0-15.0) | ||
| Used Belt | 0.55-0.67 (14.0-17.0) | ||
| 929 | |||
| New Belt | 0.35-0.39 (9.0-10.0) | ||
| Used Belt | 0.39-0.47 (10.0-12.0) | ||
| With 22 lbs. (98N) applied to belt. | |||
BELT DEFLECTION SPECIFICATIONS
CHARGING SYSTEM
| PROBLEM Possible Cause | Action | |
|---|---|---|
| NO START CONDITION | ||
| Dead Battery | Check/Replace Battery | |
| Bad Cable Connections | Clean/Replace Cables | |
| Ignition Switch/Circuit Fault | Check Switch/Circuit | |
| CHARGING SYSTEM WARNING LIGHT STAYS ON | ||
| Loose/Worn Alternator Belt | Tighten/Replace Belt | |
| Loose Alternator Connections | Check/Repair Connections | |
| Warning Light Wiring | Check/Repair Wiring | |
| Faulty Stator/Diodes | Test/Repair Alternator | |
| Faulty Voltage Regulator | Test/Repair Regulator | |
| WARNING LIGHT OFF WITH IGNITION SWITCH ON | ||
| Blown Fuse | Check/Replace Fuse | |
| Faulty Alternator | Test Alternator | |
| Bad Warning Light Bulb | Test/Replace Bulb | |
| WARNING LIGHT ON WITH IGNITION SWITCH OFF | ||
| Alternator Wiring Short | Check/Repair Wiring | |
| Faulty Rectifier Bridge | Test/Repair Alternator | |
| AMMETER INDICATES DISCHARGE | ||
| Loose/Worn Alternator Belt | Tighten/Replace Belt | |
| Loose Alternator Connections | Check/Repair Connections | |
| Faulty Ammeter | Test/Replace Ammeter | |
| NOISY Defective Battery | Replace Battery | |
| Defective Alternator | Test/Repair Alternator | |
| Defective Regulator | Test/Repair Regulator | |
CHARGING SYSTEM TROUBLE SHOOTING
TROUBLE SHOOTING PRECAUTIONS
Note. Observe the following precautions when trouble shooting or testing charging system
Miata
- Obtain code number and deactivate audio anti-theft system before disconnecting battery.
All Models
- DO NOT reverse battery cable connections. Rectifier will be damaged.
- DO NOT use high voltage type testers.
- Battery voltage is always applied to terminal "B".
- DO NOT ground terminal "L" while engine is running.
- DO NOT start engine with connector disconnected from terminals "L" and "S".
- DO NOT apply battery voltage to terminal "L".
ON-VEHICLE TESTING
Note. Check alternator wiring harness connections and drive belt tension. Battery must be fully charged before testing. Wait at least 30 seconds after starting engine before measuring system voltage.
| CAUTION | Ensure alternator terminal "B" does not contact ground. |
Scheme 2
Scheme 3
Scheme 4
- Connect an ammeter (80-amp minimum) in-line between terminal "B" connector and wire. (Scheme 2), (Scheme 3) and (Scheme 4). Turn all headlights and accessories on and depress brake pedal. With engine operating at 2500-3000 RPM, measure output amperage.
- If output amperage is not equal to or more than amount specified in ALTERNATOR OUTPUT table, repair or replace alternator as necessary.
- Turn off all accessories and release brake pedal. With engine operating at 2500-3000 RPM, measure output amperage. If output amperage is not at least 5 amps, repair or replace alternator as necessary.
- With engine operating at 2500-3000 RPM, measure voltage between terminal "S" and ground. If reading is not 14.1-14.7 volts, repair or replace alternator as necessary.
| Application | Amps | ||
|---|---|---|---|
| B2200 | 55 | ||
| B2600i | 60 | ||
| Miata | |||
| A/T | 65 | ||
| M/T | 60 | ||
| MPV | 70 | ||
| MX-6 & 626 | |||
| Non-Turbo | 70 | ||
| Turbo | |||
| A/T | 80 | ||
| M/T | 70 | ||
| MX-3 | |||
| 4-Cylinder | 70 | ||
| V6 | 90 | ||
| Protege & 323 | 65 | ||
| RX7 | 80 | ||
| 929 | 70 | ||
ALTERNATOR OUTPUT
Rectifier/Diode Assembly
- Using an ohmmeter, check continuity of each diode in both directions (polarity). (Scheme 5)and (Scheme 6). If diode shows high resistance in one direction and low resistance in other direction, diode is okay.
- If diode shows low resistance in both directions, it is shorted. If diode shows high resistance in both directions, diode is open. If any diode is defective, replace rectifier assembly.
Scheme 5
Scheme 6
Rotor & Slip Rings
Measure resistance between rotor slip ring contacts. (Scheme 7) If resistance is not within specification, replace rotor. See ROTOR RESISTANCE SPECIFICATIONS table. Check continuity between individual slip rings and rotor core/shaft. If there is continuity, replace rotor.
Scheme 7
| Application | Ohms |
|---|---|
| MPV | 2.7-2.9 |
| RX7 | 2.0-4.0 |
| All Others | 3.5-4.5 |
ROTOR RESISTANCE SPECIFICATIONS
Stator
Check continuity between stator coil leads and stator core. (Scheme 7) If there is continuity, replace stator. Check continuity between leads of stator coil. If there is no continuity, replace stator.
Brushes
Replace brushes if worn to limit line. (Scheme 7) Replace brush springs if corroded. For brush replacement procedure, see OVERHAUL.
Scheme 8
- Place a 200-watt soldering iron against rear bearing for 3-4 minutes to heat rear cover to 122-140°F (50-60°C). Carefully separate front case and rotor from rear cover and stator. (Scheme 8), (Scheme 10) and (Scheme 11).
- Position rotor in vise. Remove pulley. Disassemble pulley, rotor and front case. Remove front bearing from front case. Using a bearing puller, remove rear bearing.
- Remove "B" terminal nut and bushing from rear cover. Remove screws from brush holder and rectifier. Separate rear cover and stator. When unsoldering rectifier and stator leads, disconnect as quickly as possible (5 seconds maximum) to avoid damage to rectifier. To remove brushes from holder, unsolder pigtail from terminal.
Brush Installation
- Install brush and spring into holder. Allow brush to extend out of holder until wear limit line extends.08-.16" (2-4 mm) beyond end of brush holder. (Scheme 9) Solder pigtail onto brush holder.
- Insert spring and brush into brush holder. Using a spring scale, pull brush into holder until end of brush protrudes.08" (2.0 mm) from holder. (Scheme 9) Note reading on spring scale. Replace spring if tension is not 5.6-15.5 ozs. (160-440 g).
