HVAC Motor Not Starting or Running Weakly? Rotom Run Capacitor 36-12R3744 - Restore 12.5MFD Motor Run Capacitance

A defective motor-run capacitor is one possible cause of weak or unsuccessful motor starting in HVAC systems. The single-value run capacitor provides continuous phase-shift support to keep the motor running efficiently. When it fails, the motor may hum, struggle to reach operating speed, run intermittently, or overheat.

Common service component in residential and light-commercial HVAC fan motors and blower motor applications.

Part 36-12R3744 is the Rotom specification-based replacement rated at 12.5MFD 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 MFD, 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 12.5MFD - capacitance must match exactly
• Your original capacitor is rated 370V or 440V - a 440V replacement may replace a 370V original; the reverse is not permitted
• Your application uses a single-value round run capacitor - not a dual-run capacitor and not a start capacitor
• Your mounting space accommodates a round body approximately 1.65in in diameter and 2.78in in height

Not sure? Send us your capacitor label specs - we will confirm before you order.

Common Symptoms of a Failed Motor-Run Capacitor

• Fan or blower motor hums but fails to start
• Motor starts weakly or struggles to reach full operating speed
• Motor runs hot or trips on thermal overload
• 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, contactors, relays, motor winding failure, or electrical-supply faults - confirm the capacitor is the root cause before ordering.

Part Details

• Part Number: 36-12R3744
• Brand: Rotom / AllTemp - New
• Type: Round Single-Value HVAC Motor-Run Capacitor
• Capacitance: 12.5MFD / 12.5 uF
• Voltage Rating: 370/440 VAC (dual-voltage)
• Shape: Round
• Diameter: 1.65 in (42 mm)
• Height: 2.78 in (70 mm)
• Features: Heavy-duty compact construction, built-in interrupter, UL and cUL Recognized
• Availability: Special Order - ships in 3-5 business days
• Compatibility: Specification-based - match capacitance, voltage, shape, and dimensions to original

Also Replaces These Part Numbers

Direct round replacements (12.5MFD, 370/440V, round):
PRCF12.5 (Packard), PRCF125 (Packard), PRCF12.5A (Titan HD), TRCF12.5 (Titan Pro), CR12.5X440R (Supco), LCR12.5X440R (Supco Linebacker), 12233 (MARS Blue Box), 12733 (JARD/MARS), 45125R (DiversiTech), USA2208 (AmRad), 14833 (BMI/MARS USA), 97F5001BX (Genteq/Capcom) - electrical ratings and round shape match; case dimensions vary. Confirm mounting-strap diameter, available height and terminal clearance before ordering.

Electrical equivalents - oval case (confirm mounting fit before ordering):
36-12-370440 (Rotom, oval), POCF12.5A (Titan HD, oval), CR12.5X440 (Supco, oval), 12033 (MARS Blue Box, oval), 12933 (JARD/MARS, oval), 14033 (MARS USA, oval) - electrically compatible; oval case is not a mechanical drop-in for a round mounting bracket. A different mounting strap or bracket may be required.

Installation

Skill Level: Advanced - Qualified HVAC Technician Required. Disconnect and lock out all power before opening the electrical compartment. HVAC capacitor diagnosis and replacement should be completed by a qualified technician. Photograph the original wiring before disconnecting. Connect the replacement to the same terminals and confirm all connections are secure before restoring power and testing motor operation.

Specification Compatibility

This capacitor is compatible with any HVAC motor application that requires a round single-value run capacitor rated at exactly 12.5MFD and 370V or 440V, provided the round body (1.65in diameter x 2.78in 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.

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