OEM Control Family: Nortek / Nordyne 624631 & 903429 • Intertherm • Miller M1/M5/M7 • Frigidaire • Maytag
Nordyne, Intertherm & Miller Blink Code Decoder: Mobile Home & Residential Guide
⚡ Instant OEM Answer (Nordyne / Intertherm / Miller Red LED Codes):
Nordyne, Intertherm, Miller, Frigidaire, and Maytag furnaces use a single red diagnostic LED on the
624631 / 903429 board: 3 Flashes indicates an open Pressure Switch (clear brass inducer port and concentric roof-jack flue cap); 4 Flashes indicates an open High Limit Switch (clean louver door filter and check under-belly ducts); and 6 Flashes indicates a 1-hour Ignition Lockout (clean flame sensor below 1.0 µA DC or test 40–85 Ω spiral igniter).
Manufactured Home & Residential Reference
Nordyne / Intertherm / Miller Master Code & OEM Replacement SKU Table
Covers Intertherm & Miller downflow manufactured-home furnaces (M1MB, M1MC, M1GH, M5S, M7RL, M7TL) as well as Nortek residential furnaces sold under Frigidaire, Maytag, Gibson, Tappan, Philco, and Westinghouse badges (G6RA, G6RC, FG7SA).
| Red LED Code | Nortek OEM Fault Meaning | Nordyne / Intertherm Part SKU | Mobile Home / Residential Triage Fix |
|---|---|---|---|
| Steady Red ON | Normal Standby / Heating | 624631 / 903429 | Healthy 24V power. Check 2-wire mobile home thermostat R-W continuity. |
| 1 Flash | Low Flame Sense Signal Warning | 632484R / 903600 | Buff flame sensor rod with fine steel wool to restore > 2.0 µA DC. |
| 2 Flashes | Pressure Switch Stuck Closed | 632444R / 6323320 | Drain condensation from silicone pressure tube; replace stuck switch ($36). |
| 3 Flashes | Pressure Switch Stuck Open | 632444R (-0.55" WC) | Clear brass port on inducer; inspect mobile home concentric roof-jack pipe sleeve. |
| 4 Flashes | High Limit Switch Open | 626461R / 626338R | Wash foam louver door filter; open floor perimeter registers & check crossover duct. |
| 5 Flashes | Flame Rollout / Aux Limit Open | 626608R (Manual Reset) | CRITICAL: Inspect sealed combustion drum & concentric roof flue before resetting. |
| 6 Flashes | 1-Hour Ignition Lockout | 903110A (Spiral HSI) 624631-B / S9200U1000 |
Test 903110A igniter (40–85 Ω), check LP gas regulator freeze, or swap board. |
⚠️ HUD Manufactured / Mobile Home Sealed-Combustion Rule:
Manufactured home furnaces (
M1, M5, M7, and Coleman DGAA/DGAT) must draw 100% of their combustion air from outdoors via the concentric roof-jack assembly—never install a standard residential open-vestibule furnace in a mobile home bedroom hallway closet, and always verify proper LP propane vs. natural gas orifice conversion.