What are the specs for this Transformer?

The correct replacement for Tempstar model T9MVX100L20A1 — 115V to 24V | Ships Today is this exact part. It is the factory-specified replacement with exact OEM specifications. Using a part with different specifications can cause equipment damage or void your warranty. You can verify this by checking the data plate on your Tempstar equipment which lists the model number T9MVX100L20A1 — 115V to 24V | Ships Today.

Is this transformer compatible with Bryant or Payne systems too?

Many Tempstar parts are cross-compatible with Bryant and Payne systems since all three brands are manufactured by Carrier Global Corporation. The same physical part is often used across multiple brand labels with different model numbers. To verify cross-compatibility, check your Bryant or Payne equipment service manual for cross-compatible part numbers, or contact info@nationalhvacparts.com with your model number for confirmation.

Tempstar

Tempstar 40VA Transformer for T9MVX100L20A1 — 115V to 24V | Ships Today

Name: Tempstar 40VA Transformer for T9MVX100L20A1 — 115V to 24V | Ships Today
Brand: Tempstar
SKU: 1172810-GEN
Price: 29.00 USD
Availability: InStock

SKU: 1172810-GEN Brand: Tempstar

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Overview

This is the OEM control transformer, part number 1172810, for the Tempstar T9MVX100L20A1 two-stage variable-speed gas furnace. It steps 115V line voltage down to the 24V used by the furnace control board, thermostat, gas valve, and safety circuits, and is rated at 40VA. When a control transformer fails, the entire low-voltage side of the system goes dead: no thermostat display, no call for heat or cooling, and no 24V at the board. Transformers commonly fail from a shorted thermostat wire, a seized blower or contactor drawing excess current, or simple age. Replacing it with the correct 40VA OEM unit restores full control power.

Specifications

Spec	Value
OEM Part Number	1172810
Type	Control Transformer
Brand	Tempstar (ICP / Heil)
Primary Voltage	115V
Secondary Voltage	24V
Rating	40VA
Fits Model	T9MVX100L20A1

Compatibility

Direct-fit replacement for the Tempstar T9MVX100L20A1 100,000 BTU two-stage variable-speed furnace. This 40VA 115V-to-24V transformer is used across the ICP/Tempstar/Heil/Comfortmaker furnace family. Confirm primary/secondary voltage and VA rating against your existing transformer before installing.

Installation Guide

Safety First — Disconnect electrical power at the furnace switch or breaker. Verify zero voltage with a multimeter.
Access — Remove the furnace control/blower door to reach the transformer and control board.
Document — Photograph the primary (line) and secondary (24V) wiring before disconnecting anything.
Remove — Disconnect the primary and secondary leads, remove the mounting screws, and take out the old transformer.
Install — Mount the new transformer, reconnect primary to line and secondary to the 24V circuit per your photo.
Test — Restore power, confirm 24V at the secondary terminals, and verify the thermostat and furnace respond.

Signs You Need a Replacement

Blank thermostat and no response from the furnace.
No 24V output measured at the secondary terminals.
Blown low-voltage fuse that fails again immediately.
Burnt smell or visibly scorched transformer housing.

Shipping & Returns

Ships same day on orders placed before 3 PM CST. 30-day returns. Backed by the National HVAC Parts fitment guarantee.

Shipping Information

Orders placed before 3PM CST ship same business day
Standard delivery: 2-5 business days
Express shipping available at checkout
Free shipping on orders over $75
Tracking number emailed upon shipment

Return Policy

30-day returns on unused parts in original packaging
Electrical parts (capacitors, contactors, control boards) are final sale once installed
Email info@nationalhvacparts.com to initiate a return
Refunds processed within 5-7 business days

Tempstar 40VA Transformer for T9...

$29.00

Frequently Asked Questions

Does this Transformer fit my Tempstar T9MVX100L20A1 — 115V to 24V | Ships Today?

Yes. This is the factory-specified OEM transformer for the Tempstar T9MVX100L20A1 — 115V to 24V | Ships Today. It is a direct drop-in replacement that fits without modification. Always verify the model number on your equipment nameplate before ordering.

How do I replace the transformer on my Tempstar T9MVX100L20A1 — 115V to 24V | Ships Today?

Difficulty: Medium (30–45 min)
Step 1: Turn off breaker. Step 2: Photo wiring connections. Step 3: Disconnect wires from old transformer. Step 4: Remove mounting hardware. Step 5: Install new transformer, reconnect wires matching voltage ratings. Step 6: Verify 24V output with multimeter.

My thermostat has no power. What failed?

Thermostat with no display = failed 24V transformer (or blown control board fuse). Check the 3A/5A fuse on the control board first ($1–$5 fix). If fuse is good but no 24V output from transformer, replace transformer.

Is this transformer compatible with Bryant or Payne too?

Many Tempstar parts are cross-compatible with Bryant and Payne since all three brands are manufactured by Carrier Global Corporation. The same physical part is often used across brand labels with different model numbers. To verify: check your Bryant or Payne equipment service manual for cross-compatible part numbers, or email info@nationalhvacparts.com with your model number.

Should I use OEM or aftermarket for my Tempstar transformer?

OEM recommended for reliability and warranty compatibility. OEM parts match exact factory specifications for proper fit, performance, and safety. While aftermarket alternatives cost less upfront, the risk of improper fit and reduced lifespan usually makes OEM the better value long-term.

How fast does National HVAC Parts ship?

Orders placed before 3:00 PM CST ship the same business day. Standard delivery is 2–5 business days anywhere in the continental United States. Express shipping available at checkout. We ship from Houston, TX to all 50 states. 30-day return policy on all parts.

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