Solenoid / converter issue? Trouble with battery disconnect

Every battery disconnect I have seen uses a latching relay, most use the Intellitec one like this-


This uses no power other than switching, and is switched by reversing the polarity on the smaller posts, which uses a magnetic swing arm/spring/washer arrangement to work. I have found if it clunks when you switch it but doesn't let power through, it is usually grease inside which has solidified. They are easy to disassemble and clean.