HVAC Compressor or Fan Not Starting? Rotom Dual Run Capacitor 36-454R3744 — Restore 45/4MFD Compressor and Fan Motor Run Capacitance

A defective dual-run capacitor is one possible cause of compressor or condenser-fan starting and running problems in HVAC systems. The dual-run capacitor supports two motor circuits from one body — the compressor through the HERM terminal and the condenser-fan motor through the FAN terminal, with C as the shared common connection. When it fails, one or both motors may hum, struggle to start, operate intermittently, or overheat.

⚡ Common service component in residential and light-commercial HVAC condensing units.

Part 36-454R3744 is the Rotom specification-based replacement rated at 45/4MFD and 370/440 VAC that may restore proper motor-run support when testing confirms the original capacitor is defective and no related motor or electrical fault remains.

❓ Is This the Right Part?

Confirm the original capacitor’s MFD rating, voltage, shape and dimensions before ordering. This is the correct specification match if ALL of the following are true:

• ✔ Your original capacitor is rated exactly 45/4MFD — both values must match exactly; do not substitute a 45/5MFD capacitor
• ✔ Your original capacitor is rated 370V or 440V — a 440V replacement may replace a 370V original when capacitance matches; the reverse is not permitted
• ✔ Terminal arrangement is C / FAN / HERM (three-terminal dual-run)
• ✔ Your mounting space accommodates a round body approximately 2.36" in diameter and 4.72" in height

Not sure? Send us your capacitor label specs — we’ll confirm before you order.

🔧 Common Symptoms of a Failed Dual-Run Capacitor

• Compressor hums but fails to start or trips on thermal overload
• Condenser fan motor struggles to start or runs at reduced speed
• HVAC system short-cycles or shuts off shortly after starting
• Capacitor body visibly bulged, leaking, or reads out-of-tolerance on a capacitance meter

✔ If these symptoms match and capacitor testing confirms a defective reading, this is a likely failed component. Similar symptoms may also result from wiring, a contactor, fan motor, compressor, or electrical-supply problems — confirm the capacitor is the root cause before ordering.

📦 Part Details

• Part Number: 36-454R3744
• Alternate Rotom Number: 45/4DVR
• Brand: Rotom / AllTemp — New
• Type: Round Dual-Run HVAC Capacitor
• Capacitance: 45/4MFD / 45/4 µF
• Voltage Rating: 370/440 VAC (dual-voltage)
• Shape: Round
• Diameter: 2.36 in / 60 mm
• Height: 4.72 in / 120 mm
• Terminal Arrangement: C / FAN / HERM
• Features: Heavy-duty compact construction, built-in pressure interrupter, UL and cUL Recognized
• Compatibility: Specification-based — match both capacitance values, voltage, terminal arrangement, shape, and dimensions to original

🔄 Also Replaces These Part Numbers

Direct round replacements (45/4MFD, 370/440V, round):
45/4DVR (Rotom alternate), TRCFD454 (Titan Pro / Packard), PRCFD454 (Packard), CD45-4X440R (Supco), 12219 (MARS Blue Box, 440V), 12891 (MARS/JARD, 370/440V — current replacement for 12219), SFCAP45D4440R (Trane/SF), C4454 (GE Industrial), C4454R (GE Industrial) — electrical rating and round case match; case dimensions may differ between manufacturers. Confirm mounting-strap diameter, capacitor height and terminal clearance before ordering.

⚙️ Installation

Skill Level: Advanced — Qualified HVAC Technician Required. Disconnect and lock out all power to the condensing unit before opening the electrical compartment. HVAC capacitor diagnosis and replacement should be completed by a qualified technician. Photograph the original wiring before disconnecting. Note terminal labelling (C, FAN, HERM), connect the replacement to the same terminals, and confirm all connections are secure before restoring power and testing compressor and fan operation.

✓ Specification Compatibility

This capacitor is compatible with any HVAC condensing unit that requires a round dual-run capacitor rated at exactly 45/4MFD and 370V or 440V with a C / FAN / HERM terminal arrangement, provided the round body (2.36" diameter × 4.72" height) fits the existing mounting bracket. Compatibility is determined by electrical specification and physical fit — not by equipment model number. Contact us with your original capacitor label before ordering if you are unsure.

💡 Pro Tip