Read the rating conditions first
Identify the wire gauge, number of energized contacts, ambient temperature, and allowed rise behind the rating. Plating, crimp terminal, and housing material can change the result within one family.
Do not multiply single-contact current by pin count. Adjacent loaded contacts accumulate heat inside the housing.
- Find the temperature-rise curve
- Count simultaneously loaded positions
- Match cable-side and board-side conditions
Contact resistance changes with life
Milliohm differences in a new connector create meaningful heat at high current. Poor crimping, contamination, fretting, and mating cycles can raise resistance further.
Validation should include temperature rise after aging or cycling, not only on pristine samples.
Temperature rise is the clearest system metric. Test the final harness, housing, and airflow instead of relying only on the catalog rating.
Derate for long-term reliability
Set derating from maximum ambient, allowable housing temperature, and service life. Automotive, outdoor, and vibration environments also require sealing, corrosion, and latch-retention checks.
If margin is weak, parallel contacts, increase wire gauge, select a lower-resistance family, or separate power and signal connectors.
- Cover maximum continuous current
- Verify short peaks and thermal steady state
- Retest with production harnesses