ETA Caliber E40.305

Manufacturer	ETA
Caliber Number	E40.305
Movement Type	Quartz, analog-digital, battery-powered
Lignes	15.5”’
Diameter	35mm
Jewel Count	No jewels (0)
Battery Cell	CR 1632
Battery Life	Depends on function usage
Low Battery Indicator?	Yes
Hand Count	2
Analog Functions	Central hours; central minutes; compass
Digital Functions	Hours; minutes; seconds; date; chronograph; alarm; altimeter; thermometer
	Yes
Country of Manufacture	Switzerland, Swiss made (V8)
Known Models	Tissot T-Touch Smart Watch (Z 253/353P) (Add your watch to the comments below…)

The ETA caliber E40.305 is an ani-digi watch movement found in some early generation Tissot T-Touch watches.

Caliber Number Location:

The caliber number on the E40.XXX series of movements is not always easy to see. It should be stamped into the plastic “main frame” (as Tissot calls it) somewhere near the ETA shield logo.

Caseback Removal:

E40.305 powered T-Touch watches have a caseback which appears to have notches. It is important to know that these are cutouts for air-flow (for the thermometer, etc.), and not notches for caseback removal. The caseback is a snap-on style back that needs to be carefully pried off, not twisted off.

On the back of the caseback, will be an ultra thin micro-fiber material that is meant to be a filter between the caseback and movement. It looks like a soft and pliable plastic material, but apparently it is made from 304 stainless steel.

The “filter” allows the sensor to be exposed, so that it can calculate the pressure and temperature.

The filter protects the movement from dust and other particles, but is not made to stop water. The movement is essentially exposed to the elements, which explains why the watch only has a 30m depth-dating. Actually, 30m sounds like a lot for a watch that basically has holes in the caseback – Tissot’s tech docs literally state that “the filter allows the water to pass through but stops the foreign particles”. But also, reassuringly notes, that “the water-resistance of the movement is still maintained”.

As you’ll see below, there is a gasket protecting the battery compartment from water entry. There is also a movement gasket, not pictured.

Battery Replacement:

The battery in the cal. E40.3XX is a CR1632. You can buy CR1632 batteries here (your purchase supports this site), however, perform a DIY battery swap at your own risk (continue reading). Note: after recently ordering a pack of CR1632 batteries, the package arrived with the number ECR1632. The packaging also says the ECR1632 battery replaces the CR1632, so all good there!

There are two screws holding the battery cover in place. A 1.2mm (red) screwdriver will work for these screws.

The text on the battery cover says: BATTERY CR 1632 / 16 x 3.2 (this is the diameter and thickness in mm) / 3V

You will notice a small notch on the edge for airflow – Tissot calls it the “air evacuation canal”. It’s so air can be released when the battery cover is installed.

The battery cover itself has its own gasket as seen in the image below.

The Tissot T-Touch comes with a Swiss made Renata battery from the factory.

With the battery removed, part of the electronic circuit board is exposed:

Glued to the bottom side of the negative terminal prong, is what Tissot refers to as a “negative clamp silicone block”.

It is a small piece of silicone that gets glued to the bottom of the negative clamp/prong to ensure proper contact – in other words, to prevent the negative prong from bending down too far, losing contact with the underside of the battery cell.

When changing a battery, the silicone block will likely remain in place, but if not, they can be ordered (part number T239020090). Parts account holders were given packs of these silicone block in quantities of 500 at no charge.

Official Battery Kit:

Tissot parts account holders can order a complete battery kit which includes a new battery, a new battery cover, gasket, and two new screws (part number: T239000284).

Tissot goes as far as stating:

“To perform a battery exchange without above mentioned <Battery Exchange Kit> is prohibited. Only with this kit containing new genuine parts and the gasket specially lubricated, the water-resistance can be assured.”

If you have successfully ordered this kit from Swatch Group without a dealer or parts account, please comment below.

Service Cost:

As of 2024, Tissot lists the service price for a partial maintenance for touch-screen watches as being $65.00 USD. This is for battery replacement with “waterproofness guarantee”.

Keep in mind that any additional issues or reasons to use spare parts will cost extra.

For a complete overhaul, the prices start at $225 USD (again, these are specific prices for touch-screen watches). Tissot’s service page indicates that a complete overhaul (complete maintenance as they list it), would include the following:

“Opening of the watch case; dismantling of the crown with the winding stem so as to extract the movement with the dial and the hands. Dismantling of the movement in its individual parts, revision of the movement and replace worn movement parts, cleaning, oiling, assembling, tuning of the precision and checking the functions of the movement according to the Tissot quality standard or a movement exchange Case and metal bracelet cleaning. Replacement of the hands, crown, pushers/corrector, crystal (except shaped mineral crystals and sapphire crystals), gaskets, battery if quartz calibre. Restoration and checking of the water resistance of above mentioned parts and testing according to the Tissot specifications. Technical and aesthetical final check in compliance with the Tissot quality standard.” –Source

Pressure/Temperature Sensor:

Never touch this! The gel around the sensor is the seal. It must be intact to function correctly.

Movement Holder:

The calibre E40.305 is found in “Z352” style case models which require a locking ring which tightens the movement into the case. Other case styles held the movement in place with case clamps and screws.

The locking ring is part number T399008108. Technically it should be tightened with a torque of 4 Newtons/m.

At the time of this post, there is an eBay seller here with the locking ring for sale:

Service Note – Hands Removal/Install:

The hands on the T-Touch are made from aluminum. If you have to remove the hands, Tissot recommends replacing them with a brand new set. If you do not have access to a new set of hands, keep this in mind while removing the hands as carefully as possible.

Service Note – Case Refinishing:

Not related to the movements in T-Touch watches, but service in general: Official documentation mentions that the titanium case and bracelet of certain models (for example refs: T33.7.638.81 / T33.7.658.81) has a “grey PVD surface teatment which improves the resistance of the surface”. For this reason, Tissot does not recommend refinishing titanium T-Touch watch cases and bracelets. Doing so will remove the special PVD layer and create a difference in color and reflection from the treated surface to the refinished surface.

Service Note – Water Testing:

For Tissot T-Touch watches, only use air pressure testing machines. Do not use a water-filled tester – do not test in water.

Video – Caseback Removal, Movement Removal, Sensor Repair:

This video shows how to get into the watch, as well as how to remove the movement. Perform the actions in the video at your own risk.

Video – Functions Walkthough:

Additional Resources:

• More ETA watch movements