21778587 Wiring Harness | Genuine Volvo Penta Part

🔧 Product Description

Factory wiring harness for the D13B-E MG relay, cable and fuse installation. Connector housings, terminal positions and circuit lengths are configuration controlled and must match the engine electrical specification.

🚤 Compatibility

Typically suits:

• Volvo Penta D13B-L MP
• Volvo Penta D13B-M MP

• Engine Family: D

⚙️ Key Features

• OEM connector keying and pinout
• Correct conductor size and insulation
• Factory branch lengths and routing
• Sealed connectors where required
• EVC / voltage configuration controlled

🔌 Function

Distributes power, ground and control signals between the assigned electrical components.

⚠️ Common Signs of Failure

• Intermittent faults when the harness is moved
• Corroded, bent or backed-out terminals
• Damaged insulation or chafed conductors
• Water entry at connector seals

🛠️ Service Notes

• Compare the new harness with the old one before fitting — check the connector types, the number of pins and the branch lengths, and lay it out alongside the old loom to confirm every branch reaches its component
• Disconnect the batteries before unplugging or fitting a harness, and support the loom as you work so its weight never hangs on a connector or a bulkhead grommet
• Route it along the original path and secure it with the original clips and ties, clear of hot exhaust surfaces, sharp edges and anything that moves; leave a service loop at each connector rather than pulling a branch tight
• Push every connector home until the lock latches and protect the joints with a marine dielectric grease — an intermittent electrical fault is far more often a partly seated or salt-corroded pin than a broken wire
• Renewing the harness is the right repair where insulation is chafed, brittle or oil-soaked, or where corrosion has tracked inside the connector bodies; patch repairs in a damp engine bay tend to fail again, and any single conductor that is repaired should be joined with tinned marine cable of the same gauge, a proper crimp and adhesive-lined heat-shrink

🔄 Supersession & Cross Reference

OEM / Related Numbers

• 3587173 - relay box
• 3587172 - relay socket
• 3171420 - relay
• 874432 - related connector housings
• 20429844 - related connector housings
• 20429843 - related connector housings
• 20429842 - related connector housings

📦 Condition

• Genuine Volvo Penta part
• Brand new
• Supplied in original or equivalent packaging