Some school buses, such as the Thomas Built with a Ford chassis may be designed with no horn relay. Year and model
will determine which procedure illustrated below to use. For this type of application a five prong "Bosch" type relay must be purchased (available at P.I.C. Center).
For the purpose of this illustration we will be demonstrating the typical Ford schematic. Similar installations can be made on buses with the same problem.
Install the relay in the drivers side electrical panel.
