How Do You Replace the Brew and Steam Thermostats on a Gaggia Classic?

A stock Gaggia Classic has two snap thermostats, not one: 107 °C brew and 145 °C steam. HomeBaristaMods’ kit is that pair on an M4 brass thread, plus a spring and thermal grease, €45. Google’s first organic result for the how-to is a video; the numbers live on the parts, stamped on the terminals.

You can decide whether you are restoring the stock cut-offs or whether you actually want a PID (€169) instead.

Two temperatures, two jobs

The brew stat opens the heater when the boiler reaches about 107 °C. The steam stat is the 145 °C ceiling for the steam circuit. Mixing them up is the classic “it only steams” or “it never steams” own-goal. The value is stamped on the terminal — match it before you land a spade connector.

A thermostat is a snap switch. It is not a PID. It does not hold a 93 °C brew window. It restores the factory logic when a stat has failed open/closed or lost thermal contact.

Safety — this is a 230 V boiler circuit

The kit page is explicit: unplug, cool the machine, and verify terminals are dead with a multimeter. Thermostats sit on mains. If that sentence makes you nervous, pay an electrician. HomeBaristaMods is not your installer.

Tools the kit lists: T15 Torx, multimeter, needle-nose pliers, grease applicator. Use the E24 open-safely workflow if you need a case sequence.

What is in the €45 kit

If your old stat is not M4, stop. “Gaggia thermostat” is not one SKU across every vintage.

Grease fills the tiny gap so the snap happens at the metal temperature you think it does. A dry stat chatters and drifts.

Swap sequence (stock restore)

1. Photo every wire before you pull it.
2. Unplug. Confirm 0 V.
3. Open the case (T15).
4. Pull spades from one stat at a time.
5. Unscrew the old body. Clean the pad.
6. Thin grease on the new M4 stat. Seat it. Do not cross-thread.
7. Return the same wires to the same terminals. 107 stays brew. 145 stays steam.
8. Close up. Prime water. Watch the brew light cycle before you steam.

If the machine was dying because the brew stat failed, this is the repair. If the machine works but light roasts swing, that is the PID conversation — different part, different wiring, different money.

PID versus new thermostats

Do not buy both in one cart unless a stat is actually dead and you still want PID later. A live PID usually replaces the brew-stat’s job. Confirm the kit instructions for your generation before you parallel-wire anything.

Frequently Asked Questions

What temperature are Gaggia Classic thermostats?

The HBM replacement pair is 107 °C brew and 145 °C steam. Read the stamp on each terminal.

Can I replace a Gaggia thermostat myself?

Yes if you will unplug, cool, and meter the circuit. No if you will work live. The kit page says to use a qualified person when unsure.

Is the kit M4?

Yes — M4 male brass. Compare the old thread before you order.

Will new thermostats act like a PID?

No. They restore snap cut-offs. A PID holds a setpoint. That is the €169 kit, with offset tables on this site.

Do I need T15?

The kit’s tool list includes a T15 Torx for the case. Bring a multimeter.

References

• HomeBaristaMods: Gaggia thermostat kit (107 °C / 145 °C, M4, grease)
• Whole Latte Love: How to replace the thermostat on a Gaggia Classic (video how-to; SERP #1/#3)
• HomeBaristaMods: how to open Gaggia Classic E24 safely; PID kit PDP

Buy the restore kit from the product page, or the controller from PID kits — not one listing that pretends they are the same screw.