2 and 2-1/2 in. (51 and 64 mm.) Dial

• Corrosion Resistant Polycarbonate Case
• Indicating Gage and Limit Switch
• Switch Can Activate Alarms and/or Shut Down Equipment
• Critical/High Temperature Limit Switch Is Visible and Adjustable (Most Models)
• Contact(s) Isolated From Ground


The A20 Series (2 inch/51 mm. dial) and the A25 Series (2-1/2 inch/64 mm. dial) SWICHGAGE® models are diaphragm-actuated, temperature-indicating gages, with built-in electrical switches for tripping alarms and/or shutdown devices.

Ranges are available from 32-120°F (0-45°C) thru 300-440°F (160-220°C).

All models of these rugged, built-to-last instruments are fully sealed from the environment by the unique combination of a polycarbonate case and lens, a polished stainless steel bezel, and O-ring seals.

These vapor/pressure actuated gages feature a sealed capillary tube and a sensing bulb. When subjected to heat, the liquid in the sensing bulb changes to vapor creating pressure against a diaphragm mechanism. The diaphragm translates this vapor pressure into a mechanical gage reading.

For series A20T and A25T, the gage pointer acts as a temperature indicator and as one switch pole which completes a circuit when it touches the adjustable limit contact. Contact(s) are isolated from ground. They have self-cleaning motion to enhance electrical continuity.

Models A20TE and A25TE have internal snap-acting SPDT switches.

Gage-only models, without contacts (MURPHYGAGE®) are also available.


Applications for A20 and A25 Series temperature SWICHGAGE® instruments include: engines and equipment in Oil Field, Marine, Irrigation, Construction and Trucking industries. Monitoring Engine Coolant temperature, Crankcase Oil, Transmission Oil.




Dial: White on black; U.S.A. standard scale is dual scale °F/°C; others available.
Case: Glass filled/Polycarbonate, corrosion-resistant; steel mounting clamp included.
Bezel: Polished stainless steel, standard; others are available.
Pointer: Tempered nickel silver; red tip.
Lens: Polycarbonate, high-impact.
Sensing Element: Beryllium copper diaphragm.
Capillary: PVC armored copper; 4 ft. (1.2 m).* Galvanized and stainless steel armor optional.
Sensing Bulb: Copper.*
Gage Accuracy: See accuracy chart, on page 2.
Maximum Temperature: See Temperature Ranges and Factory Settings table on page 2.
Adjustable Limit Contact (A20T and A25T):SPST contact; pilot-duty only, 2 A @ 30 VAC/ VDC; isolated from case ground. Normally Closed when the high limit is met. Normally Open when pointer is in normal operating range. Contacts are gold flashed silver.Limit Contact Adjustment: by a 1/16 in. hex wrench thru 100% of the scale.Wiring: A20T: Number 4 screw terminals; A25T: Number 6 screw terminals.

Snap-Switch Rating (A20TE and A25TE): SPDT, 3 A@ 30 VDC inductive; 4 A @ 125 VAC inductive.Wiring: A20TE: Number 4 screw terminals; A25TE: Number 6 screw terminals.
Unit Weight: A20 Series: 11.9 oz. (0.370 kg). A25 Series Models: 13.3 oz. (0.413 kg).
Unit Dimensions: A20 Series: 4-3/4 x 4-3/4 x 3 in. (121 x 121 x 76 mm.). A25 Series Models: 4-3/4 x 4-3/4 x 2-3/4 in. (121 x 121 x 70 mm.).

Base Models

Coolant or Oil Temperature
A20T and A25T Series SWICHGAGE® For these models the gage pointer makes with an adjustable contact to complete a pilot-duty circuit.
A20TL and A25TL SWICHGAGE®  For use on Ford Worldwide engines. Supplied with special sensing bulb.
A20TE and A25TE SWICHGAGE® A20TE (was A20ESR) and A25TE (was A25ESR). Models with internal SPDT snap-switches, instead of the single pole/ pointer contact(s). When the switch closes on rising temperature, it becomes Set. As temperature decreases the switch Resets.

Model A25TE is CSA listed for non-hazardous areas. Model A25TE-EX is CSA listed for Class I, Division 1, Groups C & D hazardous areas.

A20TABS and A25TABS SWICHGAGE®  Same as 20 and 25T with internal SPDT snap-switch for pre-alarm.

Cylinder Head Temperature
A20TH and A25TH SWICHGAGE® A20TH (was A20TL8133) and A25TH (was A25TL8133). For use on Air Cooled engines.

Gage–Only Models
A20TG and A25TG MURPHYGAGE®  Gage without contact(s).

* For optional capillary lengths, engine adapters, sensing bulbs and range combinations, see Murphy bulletin T-8428B.

* * Products covered by this bulletin comply with EMC Council directive 89/336/EEC regarding electromagnetic compatibility except as noted.