Tempstar 40VA Transformer for T9MPX080J12A2 — 115V to 24V | Ships Today
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Overview
This OEM control transformer (part 1172810) steps line voltage down from 115V to 24V to power the low-voltage control circuit in your Tempstar T9MPX080J12A2 gas furnace. Rated at 40VA, it supplies the thermostat, control board, gas valve, and relays. When a transformer fails — usually from a shorted thermostat wire, a stuck contactor, or simple age — the entire 24V control system goes dead: no thermostat display, no blower, no heat. Many transformers include a resettable or replaceable secondary fuse; replacing the whole transformer is the reliable fix when the windings are open or burned.
Specifications
| Spec | Value |
|---|---|
| OEM Part Number | 1172810 |
| Type | Control / Step-Down Transformer |
| Brand | Tempstar (ICP / Heil) |
| Rating | 40 VA |
| Primary Voltage | 115 VAC |
| Secondary Voltage | 24 VAC |
| Application | Furnace Control Circuit |
Compatibility
Direct-fit replacement for the Tempstar T9MPX080J12A2 modulating gas furnace. The 1172810 40VA transformer is widely used across ICP, Heil, Comfortmaker, and Carrier-family furnaces and air handlers running the same control platform. Confirm your existing unit is rated 115V primary / 24V secondary at 40VA before installing.
Installation Guide
- Safety First — Disconnect power at the furnace switch and breaker, then verify zero voltage at the transformer leads with a multimeter.
- Access — Remove the control compartment service panel.
- Document — Photograph the primary and secondary wiring before disconnecting.
- Remove — Label and disconnect the leads, remove the transformer mounting screws, and pull the old unit.
- Install — Mount the new transformer and reconnect the 115V primary and 24V secondary leads exactly as documented.
- Test — Restore power, confirm 24V at the secondary with a meter, and verify the thermostat and control board power up.
Signs You Need a Replacement
- Blank or dead thermostat with good batteries
- No 24V output measured at the secondary terminals
- Burning smell or visibly charred transformer windings
- Furnace completely unresponsive to a heat call
Shipping & Returns
Ships same day on orders placed before 3 PM CST. 30-day hassle-free 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