AC Not Starting or Fan Not Spinning? Dual Run Capacitor 36-407R3744 — Fixes Weak Compressor or Fan Starting / Restores 40/7.5MFD Run Capacitance

If your air conditioner hums but won’t start, or the condenser fan spins slowly or only when manually pushed, a failed dual run capacitor is one of the most common causes. In most HVAC systems, the dual run capacitor supports both the compressor and the condenser fan motor from a single component. When it fails, one or both circuits lose the electrical boost needed to start and run. ⚡ Common failure point in residential central air and heat pump systems. Part 36-407R3744 is the Rotom OEM replacement that restores proper starting torque and run efficiency to both motor circuits.

🇺🇸 Matching U.S. Part Number: 36-407R3744

📦 Special Order This Part — Ships in 3–5 business days. Tracking sent once your order ships.

❓ Is This the Right Part?

This is the correct fix if ALL of the following are true:

• ✔ Unit powers on and the contactor is pulling in
• ✔ Electrical supply to the unit is confirmed OK
• ✔ Compressor or condenser fan motor is not seized
• ✔ Original capacitor is rated exactly 40/7.5MFD (not 40/5MFD, 40/10MFD or any other value)
• ✔ ONLY problem is the compressor or fan failing to start or running weakly

Not sure? Send us your model number — we’ll confirm before you order.

🔧 Common Symptoms

• AC hums but compressor won’t start
• Condenser fan spins slowly or only when manually pushed
• Unit short-cycles or shuts off shortly after starting
• Higher than normal energy bills with reduced cooling output
• Capacitor is visibly bulged, leaking, or measures out of spec

✔ If these symptoms match, this is the most likely failed component in the system.

✔ In most cases, replacing the dual run capacitor restores normal compressor and fan operation immediately.

📦 Part Details

• Part Number: 36-407R3744
• Type: Dual motor-run capacitor (compressor + condenser fan)
• Capacitance: 40/7.5 µF
• Voltage: 370/440 VAC
• Shape: Round
• Diameter: 2.36 in (60 mm)
• Height: 4.72 in (120 mm)
• Terminals: C / FAN / HERM
• Features: Built-in pressure interrupter; UL and cUL recognized
• Brand/OEM: Rotom / AllTemp
• Availability: Special Order — Ships in 3–5 business days
• Direct Round Equivalents: PPS7540440RD, PRCFD4075, PRCFD4075A, TRCFD4075, 4JR7540, TP4075440R, CD40+7.5X440R, LCR40+7.5X440R, 12287, 12787, 14287, USA2232, CD4075440, C44075R, 97F9882, 97F9882BX

⚙️ Installation

Skill Level: Moderate — 30 to 60 minutes. Disconnect and lock out power to the unit before opening the electrical compartment. Capacitors retain a hazardous charge after power is removed — discharge safely before handling. Match the terminal labels (C, FAN, HERM) exactly to the original wiring. Confirm mounting strap fit and cabinet clearance before installing — dimensions vary between equivalent brands. Diagnosis and replacement should be completed by a qualified HVAC technician.

✓ Compatible Models

Compatibility for this capacitor is specification-based. Both capacitance values must remain exactly 40/7.5MFD, and the replacement voltage must equal or exceed the original equipment requirement. Confirm the round shape and dimensions (2.36” × 4.72”) fit the mounting strap and cabinet clearance before ordering. Contact us to verify your model number before ordering.

💡 Pro Tip