Genuine Mazda FE38-15-966 Alternator Adjustment Bolt – 1.6
Replacement Genuine Mazda alternator adjustment bolt for Mazda MX-5 Mk1 NA models fitted with the 1.6-litre B6 petrol engine.
The bolt is fitted at the upper alternator mounting point and passes through the alternator adjuster spacer block. Loosening the mounting hardware allows the alternator to move along its adjustment range so the alternator and water-pump drive belt can be tensioned correctly.
Once the correct belt tension has been set, the bolt clamps the alternator securely in position. A missing, corroded, stretched or damaged bolt can prevent accurate belt adjustment or allow the alternator to move after installation.
One adjustment bolt is fitted per vehicle, and this listing supplies one Genuine Mazda bolt. The adjuster spacer block, nut, alternator mounting bolt and drive belt are separate components.
Important fitment restriction: FE38-15-966 is confirmed for MX-5 Mk1 NA 1.6 models. Mk1 1.8 and Mk2 models use a different alternator adjuster bolt and spacer arrangement.
- Part type: Alternator adjustment bolt
- Common names: Alternator adjuster bolt / belt-tension bolt / upper alternator bolt
- Mazda catalogue description: Bolt, Adjust
- Location: Upper alternator mounting and adjustment point
- Engine application: 1.6-litre petrol engine
- Engine code: B6-ZE
- Function: Secures the alternator after drive-belt tension adjustment
- Quantity fitted per vehicle: 1
- Quantity supplied: 1 bolt
- Adjuster spacer block included: No
- Retaining nut included: No
- Alternator included: No
- Drive belt included: No
- Brand: Genuine Mazda
- Part No.: FE38-15-966
- MX-5 fitment: Mk1 NA 1.6 models
Typical reasons for replacement:
- Bolt seized through corrosion
- Threads damaged during removal or adjustment
- Bolt head rounded or distorted
- Bolt bent or stretched
- Original fastener missing
- Alternator replacement or refurbishment
- Alternator bracket or spacer-block replacement
- Drive-belt tension cannot be retained correctly
Fitment advice: Confirm that the vehicle has the original Mk1 1.6 alternator mounting and adjuster arrangement. Do not assume compatibility with the Mk1 1.8 or Mk2 system, which uses different hardware.
Replacement advice: Inspect the adjuster spacer block, alternator bracket, lower pivot bolt, mounting nut and belt before installation. Damaged threads or a cracked bracket can prevent the alternator from being secured even when a new adjustment bolt is fitted.
Other items to consider: Inspect the alternator and water-pump belt for cracking, glazing or contamination. Check the alternator bearings, water-pump pulley, crankshaft pulley and all associated mounting hardware.
Useful tools / consumables: Socket and spanner set, calibrated torque wrench, penetrating fluid, wire brush, thread-cleaning tools and suitable belt-tension measuring equipment.
Difficulty guide: DIY Difficulty: Easy to Moderate. Access is straightforward, although corrosion or damaged threads may make removal more difficult. The drive belt must be tensioned correctly before the bolt is tightened.
Why Genuine Mazda? Genuine Mazda alternator hardware matches the original bolt diameter, shank length, thread specification and adjuster arrangement. Correct dimensions help the alternator move through its intended adjustment range and remain securely clamped.
What’s in the box: One Genuine Mazda alternator adjustment bolt, part number FE38-15-966.
Installation notes: Disconnect the battery before working around the alternator. Support the alternator and loosen the relevant pivot and adjustment fasteners. Remove the damaged bolt and inspect the spacer block and bracket threads. Install the replacement bolt through the original adjuster arrangement without forcing or cross-threading it. Adjust the alternator until the drive belt has the specified tension, then tighten the pivot and adjustment hardware to the applicable Mazda specification. Rotate the engine or run it briefly, recheck belt tracking and tension and confirm that the alternator remains securely positioned.
| Make | Model | Sub Variant | Chassis / Code | Years | Power (PS) | Engine Codes | Fuel | Transmission | Notes |
|---|---|---|---|---|---|---|---|---|---|
| Mazda | MX-5 | Mk1 NA – 1.6 | NA6C | 1990–1998 | 90–115 | B6-ZE | Petrol | Manual / Automatic | Upper alternator adjustment bolt; passes through the adjuster spacer block; one fitted per vehicle; 1.8 and Mk2 applications use different hardware |
| Vehicle Manufacturer | OEM Reference Number |
|---|---|
| Mazda | FE38-15-966 |