Universal External Motor-Run/Start Capacitor Mount (3D Printable)

Overview

A 3D-printed bracket for mounting a standard cylindrical AC motor capacitor externally — useful when the OEM capacitor location (often sealed inside a motor end bell) fails and there's no room, or no desire, to source an exact physical replacement. These are sometimes referred to as "starter" capacitors. Relocating the capacitor outside the housing sidesteps case-size constraints entirely: any electrically-correct replacement capacitor works, regardless of whether it matches the original's dimensions.

The design comes in two versions:

1. A zip tie version

2. A generic screw hole version for mounting

I've also included the FreeCAD design file so you can modify the original design according to your needs.

This came out of a real repair (evaporative cooler blower motor with a blown internal start capacitor), but the mount itself is generic — it fits the common cylindrical capacitor can size used across a wide range of small single-phase motors: fans, blowers, pumps, and similar fractional-HP applications.

Fitment

Designed around the standard capacitor can footprint:

• Diameter: ~1.44 in (37 mm)

• Height: ~2.75 in (70 mm)

• Terminals: 1/4" (6.3mm) male quick-connect spades

This is one of the most common capacitor case sizes on the market (covers most 189-227 MFD / 108-130 MFD start capacitors and many run capacitors in the 5-15 MFD range from brands like Supco, Packard, Appli Parts, MARS, and others), so the mount should fit far beyond the specific motor it was designed for.

Print Settings / Material

• Material: PETG recommended. Better heat tolerance and UV/outdoor durability than PLA — relevant since these mounts often end up near a warm motor housing and/or outdoors.

Installation Notes

• Mount the bracket to a rigid point near the motor (motor frame, equipment chassis, or mounting bracket).

• Orient the capacitor with terminals facing down or to the side, never straight up, to prevent water pooling on the terminals if used outdoors or in a humid environment.

• Use properly rated wire (600V+ insulation) and insulated or heat-shrink-sealed connections for any extended leads.

• This mount is a physical support only; it does not provide electrical protection. Verify your replacement capacitor matches the original's MFD/µF range and voltage rating before use.

Safety Note

This part is for mounting a capacitor in a line-voltage AC circuit. If you're not comfortable working with mains-voltage electrical systems, have this installation reviewed or performed by a qualified technician. Always disconnect power before servicing, and discharge capacitors before handling — they can retain a dangerous charge even when unpowered.