How to Troubleshoot Electric Under
Put the vehicle in park or neutral with the emergency brake on. While the engine is running, check to see if the cooling fan operates. The small fan propeller should be revolving at high speed when the engine reaches operating temperature. Toshiba Ultrasonic TransducerWait a few minutes to see if the fan comes on (some are equipped with temperature sensors and come on periodically before turning off). You must trace the problem if the fan does not operate.
Separate the wire connector that leads to the cooling fan. Make sure the connectors are clean. Place the test light probe against the positive connector point to check for 12 volt passage; the bulb inside the test light will light up when voltage flows. As an alternate method, use the battery's voltage to jump a hot (positive) lead to the inside of the connector. Ground the other wire. If no current shows using the test light, or the fan does not come on with the battery's power, the problem lies elsewhere.
Remove the top case on the small plastic relay box inside the engine compartment. The relay will be the square shaped fuse inside the box; most have an aluminum or black coloring. Pull it straight up and out. Replace it with a good used duplicate or with a new one. No fan operation after this step means the relay cannot be the problem. You also can use a small jumper wire to bridge the two connector slots where the relay plugs into the relay box connector. Non operation of a replacement relay or non operation with the jump wire means the problem lies elsewhere.