Seiko 5M45A – Technical Guide

Introduction

The Seiko 5M45A is an advanced Kinetic quartz movement introduced in the early 2000s. As an evolution of earlier 5M-series calibers (e.g., 5M42A and 5M43A), it adds a key upgrade: a 24-hour sub-dial (GMT-style indicator), in addition to the standard timekeeping and calendar features. The 5M45A is designed for sport and travel watches, offering both self-charging functionality and practical dual-time display. It is most commonly found in Kinetic Diver’s 200M and GMT models.

Technical Specifications

Key Features

Kinetic Self-Charging

The 5M45A uses an oscillating rotor to generate electricity through a miniature generator. The energy is stored in a rechargeable energy storage unit:

• Originally: Seiko capacitor 3023-5MZ

• Now recommended: MT920 lithium-ion rechargeable cell

The MT920 provides longer power reserve, better energy retention, and overall reliability.

24-Hour Sub-Dial

• Located at 6 o’clock on most models

• Functions as a day/night indicator or secondary time reference (not independently adjustable)

• Moves in sync with the main hour hand on a 24-hour scale

• Useful for tracking a second time zone or confirming AM/PM at a glance

Power Reserve Indicator (PRI)

Activated by pressing the button at 2 o’clock, the PRI uses the seconds hand jump to display stored energy:

• 5–10 seconds: ~1 day of power

• 20 seconds: ~7 days

• 30 seconds: ~1 month

• 40 seconds or more: Fully charged (~6 months)

A weak or no jump often indicates an aged or faulty capacitor or lithium cell.

Calendar and Time Setting

• Crown Position 1:

  • Rotate clockwise → quickset date

• Crown Position 2:

  • Set main time (24-hour sub-dial moves with hour hand)

• No day-of-week function

⚠️ Do not adjust the date between 9 PM and 3 AM to avoid damaging the date-change mechanism.

Reset Procedure (After Storage Cell Replacement)

After battery replacement or capacitor upgrade:

1. Install new MT920 or compatible energy cell.

2. Locate the AC (All Clear) contact pin on the movement.

3. Use plastic or anti-static tweezers to short the AC contact to the positive battery terminal for 2–3 seconds.

4. This resets the circuit and step motor control.

Servicing Notes

• Replace aging capacitors with MT920 rechargeable lithium-ion cells for improved charge retention and reliability.

• Ensure secure battery seating and proper terminal contact.

• Clean generator contacts with non-corrosive solvent (no alcohol-based cleaners).

• Avoid lubricating the rotor system unless explicitly specified in service manuals.

• Perform pressure test after resealing dive models.

Common Issues & Troubleshooting

Compatible Watch Models

The 5M45A was used in:

• Seiko Kinetic GMT Diver’s 200M models

• Seiko Sportura and Kinetic GMT sport references

• Models featuring:

  • Large stainless steel cases

  • Bold bezels

  • Luminous markers and hands

  • Screw-down crowns and casebacks

Model example prefixes:

• SKA045

• SKA291

• SKA293

• SKA301

Check casebacks marked “5M45-xxxx” for precise movement identification.

Summary Table

Conclusion

The Seiko 5M45A is a robust, multi-function Kinetic quartz movement combining Seiko’s self-charging technology with GMT-style functionality. With its 24-hour sub-dial, long power reserve, and durable design, it is ideal for travelers, divers, and collectors seeking a dependable hybrid movement. When upgraded with a modern MT920 cell and serviced properly, the 5M45A offers years of maintenance-free performance.