Openai/693478c5-5cb0-8013-9c46-dd392ce0d589

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gpt-5-1

User: Trying to help find this part.

Trying to help find this part. I can decipher "Therm-O-Disc", 2545, 9-65, 11T-42, and F-125. All I need are the temperature specs.

Assistant: What you have is a Therm-O-Disc snap-disc thermostat.

What you have is a Therm-O-Disc snap-disc thermostat. From the stampings visible:

• Therm-O-Disc = manufacturer
• F-125 = opens at 125°F (this is the trip temperature)
• 2545 = tooling / internal series identifier
• 9-65 = production date (September 1965)
• 11T-42 / 65-78 = internal lot / calibration codes

Temperature specs (the only values that actually matter in the field)

• Open (trip) temperature: 125°F (52°C)
• Reset temperature: ~20–30°F lower than trip, typically 95–105°F for this style
• Function: Automatic reset (not a one-shot fuse)
• Action: Normally closed → opens on temperature rise

Electrical class (based on terminal size and Therm-O-Disc series)

• Typical rating: 15–25 A @ 120–240 VAC Exact current rating is not encoded in the markings shown.

If you need, I can also give you:

• Direct modern replacement part numbers
• Cross-references (Supco, White-Rodgers, Packard, etc.)
• Or help confirm whether this one is being used as a limit, fan control, or safety cutout based on where it came from.

gpt-5-1-thinking

User: Cross reference would be great.

Cross reference would be great.

Assistant: Got it.

Got it. For that old Therm-O-Disc 11T-42 / F-125 disc, you’re basically just looking for:

• 3/4" snap-disc thermostat
• Auto reset
• Nominal 125°F calibration (limit or fan control)
• Same switch action (open-on-rise vs close-on-rise)

Here are practical cross-reference families you can actually buy now:

Limit-style (L125, open on rise around 125°F)

• Supco L125-xx series snap-disc limits (e.g. L125-15, L125-20) Amazon
• MARS L125-2 (open 125°F, close 105°F) Mars Delivers
• White-Rodgers 3L01-125 (3/4" disc limit series with 125°F calibration) device.report

Fan-delay / fan-control style (F125, close on rise around 125°F)

• Emerson / Therm-O-Disc 36T / 36TX F125-xxF, e.g. - 36TX22-…-F125-25F fan delay (close 125°F, open ~100°F) – sold as Marley/Q-Mark 410074000 F125-25F Fan Delay Carroll Parts

Notes so you don’t get burned (literally or figuratively):

• 11T-42 is just the old Therm-O-Disc thermostat type; modern equivalents are the 36T / 36TX style discs. Accutherm
• Manufacturers use L125 for limit controls and F125 for fan controls, but the sensing body and mounting are the same; only switch action and differential differ.
• Before choosing the exact replacement, confirm with an ohmmeter whether your original is closed or open at room temp and whether the equipment wants it to open or close on temperature rise. Then match that plus approx 125°F calibration and a similar differential (10–25°F is typical). johnstonesupply.com

If you tell me where this came from (equipment model / application and whether it’s limit vs fan), I can narrow that list to a single “grab this one off the truck” number.