HVAC Motor Starting Weak or Not Running? Run Capacitor 36-4-370440 — Fixes Weak Motor Starting / Restores 4MFD Motor Run Capacitance
If your HVAC motor hums but won’t start, runs weakly, or draws excessive current, a failed run capacitor is one of the most common causes. In PSC (permanent split capacitor) motors, the run capacitor provides continuous phase-shift support while the motor is operating. When it fails, the motor loses efficiency, struggles to start, or stops running entirely. ⚡ Common failure point in condenser fan motors, blower motors, and auxiliary motor circuits. Part 36-4-370440 is the Rotom OEM replacement that restores proper run capacitance to compatible 4MFD PSC motor circuits.
🇺🇸 Matching U.S. Part Number: 36-4-370440
❓ Is This the Right Part?
This is the correct fix if ALL of the following are true:
- ✔ Motor circuit is confirmed to require a single 4MFD run capacitor (not a dual-run capacitor)
- ✔ Electrical supply to the unit is confirmed OK
- ✔ Motor windings are not open or shorted
- ✔ ONLY problem is the motor failing to start or running below rated speed
Not sure? Send us your model number — we’ll confirm before you order.
🔧 Common Symptoms
- Motor hums but won’t start or start is sluggish
- Fan or blower runs at reduced speed
- Motor overheats or trips thermal overload
- Unit draws higher than normal current
- Capacitor is visibly bulged, leaking, or measures out of spec
✔ If these symptoms match, this is the most likely failed component in the motor circuit.
✔ In most cases, replacing the run capacitor restores normal motor operation immediately.
📦 Part Details
- Part Number: 36-4-370440
- Type: Single motor-run capacitor (not a dual-run, not a start capacitor)
- Capacitance: 4 µF
- Voltage: 370/440 VAC
- Shape: Oval
- Width: 2.03 in
- Depth: 1.24 in
- Height: 2.36 in
- Features: Built-in pressure interrupter; UL and cUL recognized
- Brand/OEM: Rotom / AllTemp
- Direct Oval Equivalents: PPS4440OV, POCF4, POCF4A, TOCF4, 45040H, TP4440, CR4X440, 12028, 12928, 14028
Inspect the motor windings and contactor at the same time. A capacitor that has failed due to age or heat stress often indicates the motor itself is approaching end of life. Confirming motor condition during the same service call prevents a repeat failure.
⚙️ Installation
Skill Level: Moderate — 20 to 45 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 connections exactly to the original wiring. Confirm oval mounting strap fit, available height 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. Capacitance must remain exactly 4MFD, and the replacement voltage must equal or exceed the original equipment requirement. Confirm the oval shape and dimensions (2.03” × 1.24” × 2.36”) fit the mounting strap and cabinet clearance before ordering. Contact us to verify your model number before ordering.
💡 Pro Tip
A 4MFD single run capacitor has two terminals and one capacitance value. If your original capacitor has three terminals (C, FAN, HERM) and two values (e.g., 35/4MFD or 45/4MFD), it is a dual run capacitor — not a single run. Installing a single run capacitor in a dual-run circuit will damage the motor. Always read the label on the old capacitor directly before ordering.
✅Compatibility & Cross Reference
Not sure about your model number? Call 1-877-899-7278 and we’ll help you confirm. All brand names are the property of their respective owners and are used for compatibility reference only.
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