Connectors and Wiring Harness Requirements 5.2.5 Harness Bends Near Connectors Avoid wire harness bends within 25 mm (1 in.) of the connector. When a harness bend is too close to the connector, the connector seal is stretched away from the wire, providing an opening for moisture entry. The wire should exit perpendicular to the connector before curving as necessary for routing. Refer to illustration in Figure 3. Figure 3: Example of Wire Harness Routing at the ECU Connector Correct AVOID Wire harness bends near a connector must be no less than twice the wire harness diameter. Special consideration shall be given to connectors with large wire counts.
Stresses placed upon the retention system of the connector can cause contact retention failures and wire pull-out. In order to avoid this problem consider the following options: 1. Pre-form the harness to the required bend. The harness assembly drawing shall detail the harness bend requirements (e.g. location and radius). The harness braid protection should be applied up to the tangent point of the bend furthest from the connector. Connector orientation to the bend may be necessary and should be specified on the harness print. 2. If harness braiding is used, increase the unbraided harness length to 150 mm.
This will allow the wires to fan out when the harness is bent, greatly reducing the forces placed on the connector contact retention system. The connector should also be oriented properly with respect to the harness so that upon installation to the product the harness will not need to be twisted to align the connector. 5.2.6 Drip Loop When a harness is routed downward to a connector, terminal block, panel, or junction box, a trap or drip loop shall be provided in the harness. This feature will prevent fluids or condensate from running into the above devices.
5.2.7 Sealing Splices and Ring Terminals Caterpillar requires all ring terminals and splices connected to the engine ECU be sealed using Raychem ES2000 adhesive lined heat shrink tubing or equivalent. Refer to Table 1 for heat shrink tubing sizing information. I N D U S T R I A L E N G I N E E L E C T R O N I C S 34