Product Overview

The Pentair 42002-0025S is a genuine OEM automatic gas shutoff (AGS) switch for Pentair MasterTemp and Sta-Rite Max-E-Therm pool and spa heaters. It is part of the heater's safety circuit: it monitors temperature inside the heater and opens the circuit when it detects excessive heat, stopping the gas valve and shutting the heater down to protect internal components from overheating.

⚠️ Important Purchase Notice

This is a heater safety control. An AGS fault does not always mean the switch has failed, so the heater should be diagnosed by a qualified pool and gas-heater technician before the switch is replaced. Never bypass, modify or remove the AGS switch from the safety circuit. Inspect the shipment upon arrival and report damage promptly.

Ideal For

• Heaters showing an AGS fault or Service Heater light where the switch has been confirmed bad.
• Heaters that start firing and then shut down, or won't complete ignition.
• A switch with no continuity after the heater has cooled.
• Pool heater technicians servicing MasterTemp and Max-E-Therm safety circuits.

Key Features

• Genuine Pentair OEM part, number 42002-0025S.
• Automatic gas shutoff safety switch, 140°F (taped).
• Interrupts heater operation when an unsafe temperature is detected.
• Direct replacement for the original factory-installed switch.

Benefits

• Restores the heater's overheat safety shutdown.
• Helps protect the heat exchanger and internal components from heat damage.
• OEM fit for a straightforward replacement.

Compatibility

Used in select models of Pentair MasterTemp (including HD and Low NOx) and Sta-Rite Max-E-Therm pool and spa heaters. Compatibility varies by model, production date, fuel type and configuration. Verify that the original switch is marked 42002-0025S and confirm your heater's model and serial number before ordering. Don't order based on an AGS fault code alone.

Installation or Upgrade Context

Before replacing the switch, check for the common causes of AGS faults: low or restricted water flow, a dirty filter, closed valves, scale in the heat exchanger, a damaged or sticking thermal regulator, bypass valve problems, improper pump speed, incorrect plumbing, or excessive gas input. Shut off power and gas, replace the switch following Pentair's service procedures, then inspect the full safety circuit, confirm water flow and test heater operation. Replacing the switch without fixing the cause of overheating can lead to another shutdown.

What’s Included

• One Pentair 42002-0025S automatic gas shutoff switch

Specifications

Warranty

Covered by Pentair’s replacement-parts warranty, subject to Pentair’s applicable terms. Eligibility may depend on proper diagnosis, professional installation and correct application; damage from bypassed safety controls, restricted water flow, scale, incorrect water chemistry or unauthorized modifications may not be covered. Contact Pentair for warranty claim instructions; Pool Supply Depot can provide proof of purchase.

Customer Q&A

What does AGS mean on a MasterTemp heater?

AGS stands for Automatic Gas Shutoff. It is a safety circuit that shuts the heater down when it detects excessive temperature.

Does an AGS error mean this switch is bad?

Not necessarily. Restricted water flow, a dirty filter, scale, a failed thermal regulator or bypass problems can all cause an AGS fault.

Does it fit every MasterTemp heater?

No. Confirm with your heater's model and serial number and the part number on the existing switch.

Can the AGS switch be bypassed?

No. It is a critical safety component and must never be bypassed.