Reply to "Fluidynine radiator temp sender"

Terminals 85 and 86 are the power inputs for the electro magnetic coil of the relay. When it gets power, it pulls the relay shut, closing the circuit between terminal 30 and terminal 87. At the same time, it will open the circuit between terminal 30 and 87a.

To turn on the fans, you want terminals 85 and 86 to receive 12 volts - one terminal (doesn't matter which, although they may be labeled + and -) will be the negative, the other one will be the positive that passes through the temp sender when it closes (reaches its set point). The two temp sensor wires are, therefore, a positive 12 source and the positive switch leg that is created when the set temp is reached and the current is allowed to pass through the temp sender; this switch leg positive is the positive source for the relay coil.

When this 12 volts hits 85 and 86, the relay pull in and will complete the 30 to 87 circuit.

The power for your fans is twelve volts from a source (it can be the same as for the temp sender) that you are sure has the amperage rating for the draw of the fans - and the fans should be wired to always receive a full time negative feed. The relay is a single pole and only switches one of the two wires needed to get power to the fans.

For the fans' positive feed, the one coming from the fuse through the relay, hook the power coming from the fans' fuse to terminal 30. Take terminal 87 and hook it to the fans' positive feed.

Done.

Terminal 87a is not used in this application.

Clear as mud? Questions?

Larry