Product Overview

The Pentair Automatic Gas Shutoff Switch 42002-0025S is a genuine OEM safety component designed for compatible Pentair MasterTemp and Sta-Rite Max-E-Therm pool and spa heaters.

Commonly referred to as the AGS switch, this component monitors heater operating temperature and helps protect the system from unsafe overheating conditions. If excessive temperature is detected, the switch interrupts heater operation to prevent continued firing until the underlying problem is corrected.

A failed or tripped AGS switch may cause the heater to stop operating and display an AGS-related fault or service-heater warning. Because an AGS error can also be caused by restricted water flow, scale buildup, a damaged thermal regulator, bypass problems, or other heater conditions, the complete system should be professionally diagnosed before replacing the switch.

Key Features

• Genuine Pentair OEM replacement component
• Automatic gas shutoff safety switch
• Helps protect the heater from excessive operating temperatures
• Interrupts heater operation when an unsafe condition is detected
• Designed for compatible Pentair and Sta-Rite pool heaters
• Direct replacement for the original factory-installed switch
• Compact electrical safety component
• Intended for professional heater repair and servicing

Compatible Heater Families

This switch is commonly used with select models in the following heater families:

• Pentair MasterTemp pool and spa heaters
• Pentair MasterTemp HD heaters
• Pentair MasterTemp Low NOx heaters
• Sta-Rite Max-E-Therm pool and spa heaters

Compatibility can vary according to heater model, production date, fuel type, and component configuration. Confirm the existing switch part number before ordering.

Specifications

How the AGS Switch Works

The automatic gas shutoff switch is part of the heater’s safety circuit. It monitors temperature within the heater and opens the safety circuit when excessive heat is detected.

When the AGS circuit opens, the heater may shut down and prevent the gas valve from continuing to operate. This protects internal components from damage caused by overheating or improper water circulation.

The switch should not be bypassed, modified, or removed from the heater’s safety circuit.

Common Symptoms of an AGS-Related Problem

• Heater displays an AGS fault
• Service Heater light is illuminated
• Heater begins firing and then shuts down
• Heater will not complete its ignition sequence
• Heater stops heating after operating briefly
• Repeated overheating or safety shutdowns
• No continuity through the AGS switch after the heater cools

An AGS fault does not always mean that the switch itself has failed. The heater should also be inspected for:

• Low or restricted water flow
• Dirty pool filter
• Closed or partially closed valves
• Scale buildup inside the heat exchanger
• Damaged or sticking thermal regulator
• Internal bypass-valve problems
• Improper pump speed
• Incorrect plumbing configuration
• Excessive gas input or combustion problems

Confirm Before Ordering

• Verify that the original switch is marked 42002-0025S.
• Confirm the heater’s complete model and serial number.
• Do not order solely based on an AGS fault code.
• Diagnose water-flow and overheating conditions before replacing the switch.
• Disconnect electrical power and gas supply before servicing the heater.
• Installation and diagnosis should be completed by a qualified pool-heater professional.

Installation Information

The heater must be completely shut down before servicing. Electrical power and gas supply should be disconnected according to the manufacturer’s service procedures.

After installation, the technician should inspect the entire heater safety circuit, confirm proper water flow, and test heater operation. Replacing the AGS switch without correcting the condition that caused the overheating may result in another shutdown or damage to the heater.

Never bypass the AGS switch to keep the heater operating.

Warranty Information

This genuine Pentair replacement part is covered according to Pentair’s applicable replacement-parts warranty terms. Warranty eligibility may depend on proper diagnosis, professional installation, correct application, and compliance with Pentair’s installation and service requirements.

Damage caused by improper installation, bypassing safety controls, restricted water flow, scale buildup, incorrect water chemistry, or unauthorized heater modifications may not be covered.

Customer-Facing Q&A

What does AGS mean on a Pentair MasterTemp heater?
AGS stands for Automatic Gas Shutoff. It is a safety circuit that shuts the heater down when an excessive-temperature condition is detected.

Does an AGS error mean this switch is defective?
Not necessarily. An AGS fault may also be caused by restricted water flow, a dirty filter, scale buildup, thermal-regulator failure, or internal bypass problems.

Does this switch fit every MasterTemp heater?
No. Compatibility should be confirmed using the heater model, serial number, and the part number printed on the existing switch.

Can the AGS switch be bypassed?
No. The switch is a critical safety component and must never be bypassed or removed from the heater’s safety circuit.

Is professional installation recommended?
Yes. Pool-heater safety controls should be diagnosed and replaced by a qualified pool and gas-heater technician.