Rotom HVAC Dual Run Capacitor 36-405R3744, Round 40/5MFD 370/440V

The Rotom 36-405R3744 is a specification-based round dual-run HVAC capacitor rated at 40/5MFD and 370/440 VAC. It 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 the original capacitor fails, one or both motors may hum, struggle to start, operate intermittently, or overheat. This is a specification-based replacement — compatibility is determined by electrical rating and physical fit, not by equipment model number.

Is This the Right Part?

Confirm MFD, voltage, shape, and dimensions before ordering. 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.

Common Symptoms

• 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 is visibly bulged, leaking, or reads out-of-tolerance on a capacitance meter
• One or both circuits (compressor or fan) fail while the other continues to operate

Check Before Replacing

• Test both capacitance values (40MFD and 5MFD) separately with a dedicated capacitor tester — confirm a defective reading before ordering
• Inspect the contactor for pitting or burning — a worn contactor is a common co-failure with a capacitor in aging condensing units
• Check wiring and terminal connections — loose or corroded terminals cause identical symptoms without capacitor failure
• Verify the original capacitor label matches 40/5MFD and 370V or 440V before ordering — MFD values must match exactly
• Confirm the round body (2.36in diameter × 4.72in height) fits the existing mounting bracket and cabinet clearance

Part Details

Cross-Reference Part Numbers

Direct round replacements (40/5MFD, 370/440V, round): PRCFD405 (Packard), PRCFD405A (Titan HD), TRCFD405 (Titan Pro), PPS540440RD (ProParts standard), PPHD540440RD (ProParts HD), TP405440U (TradePro), 4JR0540 (DiversiTech), CD40+5X440R (Supco), 12286 (MARS), 12786 (JARD/MARS), USA2235 (AmRad), 97F9838 (Genteq/Capcom), C4405R (Genteq/Capcom). Electrical ratings and round shape match; diameter and height vary — confirm mounting strap diameter, cabinet clearance, and terminal clearance before ordering.

Electrical equivalents — oval case (confirm mounting fit before ordering): 36-40-5-3744 (Rotom, oval, manufacturer-discontinued), POCFD405A (Titan HD, oval), TOCFD405 (Titan Pro, oval). Electrically equivalent; oval case is not a mechanical drop-in for a round mounting bracket.

370V-only references — do not use in 440V applications: PRCD405, CD40+5X370R (Supco), 12178, 12878, 3GR0540, 97F9849, C3405R (round); 12171, 3GJ0540 (oval). Use only when the equipment originally specifies a 370V capacitor.

Installation Notes

1. Disconnect and lock out all power to the condensing unit before opening the electrical compartment.
2. Photograph the original wiring and terminal connections before disconnecting.
3. Note terminal labelling (C, FAN, HERM) and connect the replacement to the same terminals.
4. Compare the new capacitor dimensions with the original — confirm it fits the mounting bracket before installing.
5. Restore power and test compressor and fan operation before closing the unit.

HVAC capacitor diagnosis and replacement must be completed by a qualified HVAC technician. Capacitors store a lethal charge even after power is disconnected — discharge the capacitor safely before handling.

Verified Compatible Models

No verified exact equipment models confirmed. Specification-based HVAC replacement: 40/5MFD, 370/440 VAC, round case. Verify both capacitance values, voltage, terminal arrangement (C/FAN/HERM), and dimensions before ordering. Contact us with your original capacitor label to confirm before ordering.

Fitment reminder: Compatibility is determined by electrical specification and physical fit — not by equipment model number.