Retention Test Tools: What they are and why they are important?

Retention Test Tools are an important yet often overlooked component to proper quality control.

A contact retention tester confirms a connector's contact, either the pin or socket, meets the connector manufacturer's rating for how much force the contact must be able to take while still being fully locked in place against the tine and without resulting in a 'dropped contact'. These values vary based on the connector type and contact type, in other words not all Size 20 contacts carry the same rating. Retention force requirements range from 10lbf to 25lbf in most standardized contact sizes.

Exploded Circular Connector


Autosport Connector Tine Close Up

This tool can be likened to how a torque wrench measures the amount of force, typically in lb-ft or Nm, you are subjecting on a nut or bolt. DMC Tool's retention testers measure in lbf (pound-force), and achieve this by the specific spring tension inside the tool. There are catalog retention testers for specific connector series that we stock and there are also custom solutions DMC has produced for us for everything from Size 26 to Size 4 contacts.

Most of the contact retention testers we carry for Deutsch Autosport and Souriau 8STA connectors include the tester (tool body) with a double ended design including the appropriate tips for both male (pin) and female (socket) contacts, a palm grip cover to use as the 'handle', and a plastisol protective tip cover.

To use these, simply put the tool's appropriate tip over the contact you are checking and press down on the tool until the machined 'pass' line of the contact tip meets the tool's body. As this occurs, the tool is subjecting the pre-defined force on the contact to ensure the connector's tine is retaining the contact appropriately. Some specific testers have a different 'pass' line marking, but the same principle applies. Due to the relatively low force these testers must output, it is important to maintain calibration dates and records to ensure they do not come out of spec and if they do, recalibrate them.

While Deutsch Autosport, Souriau 8STA, and MIL-Spec connectors are produced with strict quality control guidelines and are rated up to 500 mating cycles, it is not all that uncommon to have the dreaded 'dropped contact' be realized only when it's too late and a boot has already been installed. There is no repair for this, a new connector must be fitted and the original connector discarded which can be quite painful after finishing up terminating a 100-way connector! Tine failure can happen due to manufacturer defects causing cracking of the tine mechanism, improper use of insertion/extraction tools, foreign objects being used for insertion/extraction, and on occasion...they are even missing entirely.

This very simple quality control process can be implemented at any level of wiring and is cheap insurance when compared to the result of an unknown dropped contact causing intermittent or no connection on any number of circuits in your connector. The contact drop can happen on the connector's first mating, within a half hour of run time, or after a few mating cycles - the only way to be sure you avoid this is to test before the assembly is put into use.