Relay socket connectors

I just got a new power supply for my bench testing of my products. This new supply is an adjustable 0 to 15 volt 0 to 60 amp. supply capable of constant voltage or constant current. So to test the new supply I connected one of my fan relays and made up power and load cables using six 16 AWG wires on each branch. I ran 60 amps for 5 minuets just to verify the supply was working and test what could fail.

Well my relay has no problems with 60 amps of current but the relay pins and their connector sockets are what produce the most heat. By the end of that 5 minuet run the pins were getting hot, the relay was just getting warm and the wires were getting warm. So now I know why the 70 amp AUX relays use larger pins on the load connections.

I use my electronic relays replacing the AUX relays but use the standard size pins (I've added sockets to my harness). But I tested the AUX circuit currents and they are well below 30 amps each.

My test socket pins are very heavy gauge metal (made for 8 AWG wire). You could never put those pins into a socket because it takes so much force just to push one pin on or off.

This is just an FYI as to why some people get melting fan fail sockets.

My guess on the weak link would be the crimp where the connectors attach to the wires. That is a very critical operation and to be done correctly requires the exact right equipment and must be quality checked frequently. I doubt the proper level of attention was paid to that when the harnesses were made. Then add 30 + years of heating and cooling cycles and oxidation. One way to verify this would be to solder the connection and see if it heats up as much or as fast. It also wouldn't hurt to look up the specs for the connector to see what it was designed for. It is possible it is just not up to the task and cannot carry that level of current. Those connectors count on the strength of the materiel to maintain the crimp and the connection (grip) to the blade of the relay. Overheat them and you lose that grip. Once you lose the grip the connection gets worse so it gets hotter and the cycle repeats till failure. I am guessing here but to "upgrade" the connections you can solder the connector to the wire and there are compounds you can put on the blades of the relays to improve conduction, lower resistance, and prevent oxidation. Both steps may be enough to make things last longer.

Yes the crimps are another critical point of failure. The proper crimp on the open barrel pins is very reliable. My test setup has all the crimp joints soldered because I was probably exceeding design currents.

Socket terminals are AMP FASTON terminals and the spec. sheets do not rate current.
Pin terminals are AMP and spec. sheet does not rate current.