CAT 9D3721 SWITCH for C18 Caterpillar Part - WSTPARTS
WSTPARTS supplies the 9D3721 SWITCH, a CAT Switch/Relay replacement part designed for Caterpillar C18, 3516B and C15 applications. It is categorized under Switch/Relay. Every unit is fitment-verified before dispatch. Manual reference: 3306: ELECTRICAL AND STARTING SYSTEM, group 133-9670, page 1341; 3412C: ELECTRICAL AND STARTING SYSTEM, group 143-9781, page 452.
9D3721 SWITCH for Caterpillar C18 — Genuine CAT & Replacement Part
WSTPARTS supplies genuine CAT and OEM-equivalent direct-replacement SWITCH (Part # 9D3721). Designed for CAT C18, 3516B, C15, 3306, 3412C, G3508 equipment.
Compatible Models
Key Features
- ✔ 100% compatible with CAT C18, 3516B, C15, 3306, 3412C, G3508
- ✔ Meets Caterpillar original quality and performance standards
- ✔ Genuine CAT lines: New Genuine / Cat Reman / Cat Classic | OEM-equivalent direct replacements
- ✔ Available for order, contact for lead time
Specifications
| Part Number (MPN) | 9D3721 |
| Product Name | SWITCH |
| Brand | CAT |
| Applicable Models | C18, 3516B, C15, 3306, 3412C, G3508 |
| Weight | 0.05 kg |
| Condition | New (Genuine CAT / OEM-equivalent direct replacement) |
| Warranty | 12 Months |
Where This Part Fits
Every row below is a real listing of 9D3721 in the Caterpillar parts manual: the machine it is published under, the system it belongs to, the group number and the manual page. Use it to confirm the part against your own parts book before ordering.
| Machine | System | Group No. | Manual Page |
| 3306 | ELECTRICAL AND STARTING SYSTEM | 133-9670 | p.1341 |
| 3412C | ELECTRICAL AND STARTING SYSTEM | 143-9781 | p.452 |
| 3516B | ELECTRICAL AND STARTING SYSTEM | 121-4718 | p.709 |
| C15 | ELECTRICAL AND STARTING SYSTEM | 270-5000 | p.412 |
| C18 | ELECTRICAL AND STARTING SYSTEM | 236-7859 | p.329 |
| G3508 | ELECTRICAL AND STARTING SYSTEM | 149-8733 | p.583 |
| 3306 | OPERATOR STATION | 103-4773 | p.1766 |
| 3516B | ELECTRICAL AND STARTING SYSTEM | 252-7424 | p.758 |
System Notes — ELECTRICAL AND STARTING SYSTEM
The electrical and starting system covers the battery, starter motor, alternator, wiring harness, relays, switches and the instrument panel. It carries current from the batteries to the starter to crank the engine, and from the alternator back to keep the batteries charged. Because these machines work in dust, vibration and wide temperature swings, connectors corrode, harness insulation chafes against the frame, and starter solenoids burn out from repeated short cranks. Parts in this group are usually replaced on a symptom basis — slow cranking, a dash warning, lights that dim under load, or a no-start condition traced to an open circuit.
System Notes — OPERATOR STATION
The operator station covers the cab structure, seat and suspension, glass, wipers, door hardware, pedals, joysticks, armrests, HVAC ducting and the interior trim. It is the group that decides how tolerable a ten-hour shift feels. Wear here is driven by daily entry and exit, sun exposure and dust: seat suspensions sag, door struts lose charge, wiper linkages seize, and rubber seals harden until the cab leaks in rain. Parts in this group are replaced when a control feels vague, a latch no longer holds, or the cab no longer keeps dust and water out — small items, but the ones operators complain about first.
FAQ
Is 9D3721 the right part for my machine?
Match the part number on your old part, or send us your equipment serial number — WSTPARTS verifies fitment free of charge for CAT C18.
Genuine CAT vs direct replacement — what is the difference?
Genuine CAT covers three factory lines: New Genuine, Cat Reman (core exchange with core charge) and Cat Classic (brand-new economy line). OEM-equivalent direct replacements are non-CAT parts; grade and warranty are confirmed in the quotation.
Stock, shipping and warranty?
Lead time confirmed on request; we quote the fastest available option. Every order is covered by a warranty per quotation.
📞 Get a Quote: Contact the WSTPARTS parts team | Email: cat@wstparts.com
