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I'm working on repairing a swimming pool hot tub heater. Feed is 240v 1Ph A/C power and it uses 18 gauge wire throughout. Apparently something got wet and I can see signs of a thermal event within the an electrical connector joint. I'm replacing the connector and the terminals with all new ones. (And yes, I will check for other potential shorts before I power this puppy up. My initial guess is it was powered up during a rainstorm, and the water caused the fault. )

The terminal system is the "Universal Mate-n-Lok" AMP from TE Connectivity. Male/female hardshell connectors, and their corresponding terminal pins/sockets are readily available from electronics supply warehouse stores.

I see they offer "split-pin" and non-split pin designs. The "split-pin" design is clearly designed for an bit 'more' of interference fit... its "in phase O.D." = 2.21 to 2.08mm The non-split pin design has an O.D. of 2.13 to 2.07mm. (Female terminal I.D. is 2.06 to 1.98mm) I can't find anything from the manufacturer on usage recommendations on the two different designs. Reference, MFGR PN: 350218-1 and 350687-1

Solid Pin Design

Split Pin Design

So here are my dumb questions. Split pin or non split pin? The prices are exactly the same. Why that choice? And if it doesn't make any difference, and they both perform the same, then why did the manufacturer tool them up that way in the first place?

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From Tyco Electronics Soft Shell Pin and Socket Connectors, page 173.

"Notes: 1. Split pins recommended for use in housings having 6, 9, 12 and 15 circuits to reduce mating force."

If you look at the TE document 110-213, page 3 under Mating force, you can see that the split pin has less than 1/3 the mating force than the solid pin.

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It is called a bifurcated contact and the reliability of redundant contacts improves significantly, so if one fails at least another is available. But it gets more complicated with varying insertion and extraction forces, so the non-split "may be " better for secure retention forces. Then there is plating removal and insertion cycle ratings. In this case, one insertion is all you need BUT you want it secure and moisture proof, so coat the connector in silicon or RTV for a poor-man's waterproof connector.

Dust + scraped plating + chlorinated water = corrosion and early failure.

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