AC Not Starting or Fan Not Spinning? Dual Run Capacitor 36-253R3744 — Restores 25/3MFD Compressor and Fan Motor 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 36-253R3744 is the Rotom OEM replacement that restores proper starting torque and run efficiency to both motor circuits.
🇺🇸 Matching U.S. Part Number: 36-253R3744
📦 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 25/3MFD (not 25/4MFD, 25/5MFD 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: 36-253R3744
- Type: Dual motor-run capacitor (compressor + condenser fan)
- Capacitance: 25/3 µF
- Voltage: 370/440 VAC
- Shape: Round
- Diameter: 1.97 in (50 mm)
- Height: 3.54 in (90 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: PRCFD253, PRCFD253A, TRCFD253, LCD25+3X440R, 12353, 12653, 14353, USA2224BA, C4253R
Inspect the contactor at the same time. A worn or pitted contactor is a common companion failure in systems where the capacitor has failed — replacing both during the same service call prevents a repeat call-back.
⚙️ 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 25/3MFD, and the replacement voltage must equal or exceed the original equipment requirement. Confirm the round shape and dimensions (1.97” × 3.54”) fit the mounting strap and cabinet clearance before ordering. Contact us to verify your model number before ordering.
💡 Pro Tip
The 3MFD fan section is less common than 4MFD or 5MFD. Both values must match exactly — a 25/4MFD or 25/5MFD capacitor is not a substitute even if the voltage and shape match. Always read the label on the old capacitor directly rather than relying on the unit’s model number alone.
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Kitchener, Ontario N2E 1W8
