Caterpillar 345B External Wiring Harness
External Wiring Harness for Caterpillar 345B excavator. OEM part 128-3774. Direct replacement.
Fitment
Fits the Caterpillar 345B Excavator. ECS lists 12 harness sections for this machine — see all 12 sections for the Caterpillar 345B before you order, because the sections are not interchangeable.
Part number reference for the 128-3774
This harness is one part sold under one number. Suppliers and parts books write it differently — you may see it as 128-3774, 1283774 · CA1283774. They are all the same part; the number on the tag of your old harness is what settles the order.
If the tag shows a different number entirely, do not order by eye — send us a photo of it on WhatsApp and we will match it against the catalogue before anything ships.
Where this harness sits on the Caterpillar 345B
It is the outside harness on the machine body — exposed to rain, wash-down, mud and UV. On most machines it is the section most often replaced.
What it connects
- Cab and engine circuits to the machine body — the link between the enclosed sections and everything mounted outside.
- Body-mounted components — lights, sensors, valves and switches that sit outside the cab.
What a failing Caterpillar 345B harness looks like
| What the operator reports | Why the harness fits that symptom |
|---|---|
| Several circuits dead after rain or a wash | Water ingress at an outside connector. |
| Green corrosion at the plugs | The first visible sign; the strands behind the pin are usually worse. |
| Intermittent faults on rough ground | A loom that has lost its clips and is rubbing the frame. |
| One function fails, then another | Corrosion spreading through a shared connector. |
These are circuit-level symptoms, not a diagnosis. The same behaviour can come from a sensor, an ECM input or a mechanical fault — the checks below are how you tell them apart.
How to confirm it is the harness before you buy
- Compare the part number on the old harness. The number is printed on a tag or moulded into the main connector body. If it does not match, stop — stop here and send us a photo, because two sections of the same machine are not interchangeable.
- Resistance test the suspect run. Disconnect both ends and measure end to end. A reading that is far above the others in the same loom means broken strands; a reading to ground means chafing.
- Wiggle test under load. Back-probe the circuit with the machine running and flex the loom by hand along its length, especially at clips and at the cab or boom entry. If the meter or the fault jumps, you have found the run.
Other harness sections for the Caterpillar 345B
Same type of harness on other machines
Product Description
External Wiring Harness for Caterpillar 345B excavator. OEM part number 128-3774. Direct replacement ensuring plug-and-play installation.
Why Choose ECS System Parts?
- Factory Direct: we build the loom — no middlemen
- In Stock Ready to Ship: most orders leave within 24 hours
- OEM Quality: made to the original drawing, connector for connector
- 1 Year Warranty: full coverage against defects
- Worldwide Shipping: DHL, FedEx, UPS, EMS
- Expert Support: WhatsApp +86-13714733803 — send us a photo of your old harness and we will confirm the section
Technical Specifications
| OEM Part Number | 128-3774 |
|---|---|
| Compatible Model | Caterpillar 345B Excavator |
| Harness Type | External |
| Warranty | Packaging Machine Normal Use |
Shipping Information
- DHL / FedEx / UPS / EMS worldwide
- Ships within 24 hours
- 3-7 days express, 7-15 days standard
- Tracking number provided
Return Policy
- 30-day return window
- Must be unused, original packaging
- Contact via WhatsApp for RMA authorization