1991 MAZDA MIATA alternator

ALTERNATOR OUTPUT
BENCH TESTING
Rectifier/Diode Assembly
1. Using an ohmmeter, check continuity of each diode in both directions (polarity). See Fig. 5 and Fig. 6. If
diode shows high resistance in one direction and low resistance in other direction, diode is okay.
2. If diode shows low resistance in both directions, it is shorted. If diode shows high resistance in both
directions, diode is open. If an
y diode is defective, replace rectifier assembly.
ApplicationAmps
B220055
B2600i60
Miata
A/T65
M/T60
MPV70
MX-6 & 626
Non-Turbo70
Turbo
A/T80
M/T70
MX-3
4-Cylinder70
V690
Protege & 32365
RX780
92970

1991 Mazda MX-5 Miata
ALTERNATOR & REGULATOR 1990-92 ELECTRICAL Alternators & Regulators - Mitsubishi
Microsoft
Sunday, July 05, 2009 2:14:54 PMPage 8 © 2005 Mitchell Repair Information Company, LLC.

Fig. 5: Testing Alternator Rectifier & Diodes
Courtesy of MAZDA MOTORS CORP.
Fig. 6: Testing Alternator Rectifier & Diodes (1992)

Courtesy of MAZDA MOTORS CORP.
Rotor & Slip Rings
Measure resistance between rotor slip ring contacts. See Fig. 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 continuit
y, replace rotor.

1991 Mazda MX-5 Miata
ALTERNATOR & REGULATOR 1990-92 ELECTRICAL Alternators & Regulators - Mitsubishi
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Fig. 7: Testing Alternator Stator, Rotor & Brushes
Courtesy of MAZDA MOTORS CORP.
ROTOR RESISTANCE SPECIFICATIONS
Stator
Check continuity between stator coil leads and stator core. See Fig. 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. See Fig. 7 . Replace brush springs if corroded. For brush replacement
procedure, see OVERHAUL.
OVERHAUL
DISASSEMBLY
1. Place a 200-watt soldering iron against rear bearing for 3-4 minutes to heat rear cover to 122-140°F (50-
60°C). Carefull
y separate front case and rotor from rear cover and stator. See Fig. 8 , Fig. 10and Fig. 11.
ApplicationOhms
MPV2.7-2.9
RX72.0-4.0
All Others3.5-4.5

1991 Mazda MX-5 Miata
ALTERNATOR & REGULATOR 1990-92 ELECTRICAL Alternators & Regulators - Mitsubishi
Microsoft
Sunday, July 05, 2009 2:14:54 PMPage 10 © 2005 Mitchell Repair Information Company, LLC.

Fig. 8: Overhauling Alternators
Courtesy of MAZDA MOTORS CORP.
2. 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.
3. 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.
REASSEMBLY
Brush Installation
1. 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. See Fig. 9
. Solder pigtail onto brush holder.
2. 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. See Fig. 9
. Note reading on spring scale. Replace spring if tension
is not 5.6-15.5 ozs. (160-440 g).

1991 Mazda MX-5 Miata
ALTERNATOR & REGULATOR 1990-92 ELECTRICAL Alternators & Regulators - Mitsubishi
Microsoft
Sunday, July 05, 2009 2:14:54 PMPage 11 © 2005 Mitchell Repair Information Company, LLC.

Fig. 9: Measuring Installed Depth of Brush
Courtesy of MAZDA MOTORS CORP.
Fig. 10: Exploded View of Alternators

Courtesy of MAZDA MOTORS CORP.

1991 Mazda MX-5 Miata
ALTERNATOR & REGULATOR 1990-92 ELECTRICAL Alternators & Regulators - Mitsubishi
Microsoft
Sunday, July 05, 2009 2:14:54 PMPage 12 © 2005 Mitchell Repair Information Company, LLC.

Fig. 11: Exploded View of Alternators
Courtesy of MAZDA MOTORS CORP.

1991 Mazda MX-5 Miata
ALTERNATOR & REGULATOR 1990-92 ELECTRICAL Alternators & Regulators - Mitsubishi
Microsoft
Sunday, July 05, 2009 2:14:54 PMPage 13 © 2005 Mitchell Repair Information Company, LLC.

1990-93 ENGINE COOLING
Drive Belt Routing & Adjustment - MX-5 Miata
ADJUSTMENT
Fig. 1: Identifying Correct Belt Mounting
Courtesy of MAZDA MOTORS CORP.
ALTERNATOR
Loosen alternator bolts and adjust belt deflection by turning adjusting bolt. See Fig. 2
, Fig. 6 and Fig. 7 . See
ADJUSTMENT SPECIFICATIONS
. Tighten bolts to specification. See TORQUE SPECIFICATIONS. NOTE: Ensure drive belts are not worn, cracked or frayed and are correctly mounted
on pulleys. See Fig. 1
.
NOTE: If a new belt is used, adjust belt deflection at midpoint of new belt specification.

1991 Mazda MX-5 Miata
1990-93 ENGINE COOLING Drive Belt Routing & Adjustment - MX-5 Miata

1991 Mazda MX-5 Miata
1990-93 ENGINE COOLING Drive Belt Routing & Adjustment - MX-5 Miata
Microsoft
Sunday, July 05, 2009 2:14:16 PMPage 1 © 2005 Mitchell Repair Information Company, LLC.
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Fig. 2: Adjusting Alternator Belt
Courtesy of MAZDA MOTORS CORP.
A/C COMPRESSOR
Loosen locknut and adjust belt deflection by turning adjusting bolt. See Fig. 3
, Fig. 6 and Fig. 7 . See
ADJUSTMENT SPECIFICATIONS
. Tighten bolts to specification. See TORQUE SPECIFICATIONS.

1991 Mazda MX-5 Miata
1990-93 ENGINE COOLING Drive Belt Routing & Adjustment - MX-5 Miata
Microsoft
Sunday, July 05, 2009 2:14:16 PMPage 2 © 2005 Mitchell Repair Information Company, LLC.