dual sourcing, alternate source, second supplier, multi-sourcing, supply redundancy
Second sourcing is a design-time decision with a procurement-time payoff. During development a part is chosen, and someone decides whether an alternative will be qualified alongside it. If nobody does, the part is single-sourced, and its supplier now holds a veto over the programme.
The qualification is the work. A second source has to be tested and approved against the same requirements as the first, added to the AML or AVL, and reflected on the drawing. Doing that before there is a crisis takes weeks. Doing it during a crisis takes the same weeks, except that the line is down for them.
Connectivity components are frequently single-sourced by their nature. Connector systems are proprietary. A TE MQS housing mates with MQS terminals, and no other manufacturer makes a legitimate part that mates with it. The realistic second source is therefore often not a second manufacturer of the same part, but a second channel to the same manufacturer's part: another distributor, another region, the open market.
That reframes the question worth asking. For a proprietary connector family, redundancy means supply redundancy rather than manufacturer redundancy. Knowing in advance who can find the part when the normal channel cannot is the practical equivalent of a second source, and establishing that relationship costs nothing before it is needed and a great deal afterwards.
Harness Code is used that way by harness manufacturers and Tier 1 suppliers: not as a replacement for the authorised channel, but as the route that stays available when the authorised channel has no date to give.
Related terms
Franchised vs independent distributor
A franchised or authorised distributor holds a contract with the manufacturer and buys directly from the factory. An independent distributor has no such contract and sources from the open market: excess inventory, other distributors, and stock outside the manufacturer's direct channel.
Cross-reference and drop-in equivalent
A cross-reference maps one manufacturer part number to a comparable part from another family or another manufacturer. A drop-in equivalent is a cross-reference matching on form, fit and function, usable without any change to the harness, the tooling or the mating half.
Allocation and lead time
Allocation is when demand for a component exceeds supply and the manufacturer rations output across customers instead of quoting freely. Lead time is the interval between placing an order and receiving it. When a part goes on allocation, its lead time stretches and stops being a promise.
Approved Vendor List (AVL) / Bill of Materials (BOM)
A Bill of Materials (BOM) is the complete list of parts and quantities needed to build a product. An Approved Vendor List (AVL) names the manufacturers and suppliers a buyer is permitted to source those parts from. The BOM says what; the AVL says from whom.