Note the relay position. The positioning and polarity of relays and fuses should be printed on the inside of the relay box or fuse box cover. Note the position of the relay that was removed so that it may be replaced in the proper position and orientation.
Identify the relay as an ISO mini type. The International Standards Organization (ISO) defines this type of relay as 1 inch (2. 5 cm) square (25. 4 mm square). ISO defines mini relays with the control circuit connected to pin 86 and pin 85, and the load circuit connected to pin 30 and pin 87 or 87a. There will be only 1 second load pin, 87 or 87a, not both. Determine that the relay is an ISO micro type. The ISO defines this type of relay as 1 inch (2. 5 cm) by 1 inch (2. 5 cm) by 0. 5 inches (25. 4 mm by 25. 4 mm by 12. 7 mm). An ISO micro relay has the control circuit connected to pin 86 and pin 85, and the load circuit connected to pin 30 and pin 87 or 87a. There will be only 1 second load pin, 87 or 87a, not both. Read the relay connections printed on the relay. The control circuit will be depicted as a coil of wire on the surface printing of the relay. The load circuit will be depicted as straight lines with a dot or circle on the end of one of the lines. If the 2 lines are depicted as not connecting at the circle or dot, the relay is a normally open (NO) relay. If the 2 lines are depicted as meeting at the circle or dot, the relay is a normally closed (NC) relay. It is important to know if the relay is NO or NC during further testing. Determine if the relay is internally protected against voltage spikes. A relay with internal protection will have a diode symbol shown on the package drawing connected around the control coil. The diode symbol will be a triangle with a line attached perpendicularly to 1 of the points. The line shown on the diode symbol will indicated the positive polarity end of the diode.
