How are Fog Lamp Relay issues diagnosed?
To diagnose a bad fog lamp relay, a technician will first rule out other possible causes of intermittent or inoperative fog lamps. Simple causes, such as a blown fuse, are checked first. The bulbs in the fog lamps will wear out and need replacement eventually, so the technician will check those. If the fuse and the bulbs are good, the technician will pull the relay from its mounting location and use a multimeter to check the electrical connections for voltage. If voltage is present, the technician will check the resistance across the terminals of the relay and might test the relay by applying power to it. In some cases, the problem might originate in the ECM. In these cases, the technician will look for a diagnostic trouble code (a fault code) that can be read with a scan tool.
How are Fog Lamp Relays replaced?
Replacement of the fog lamp relay is simple in most cases. It is usually located in a fuse block under the hood. With the hood and the fuse block opened, the technician locates the relay, pulls it out, and installs a new relay.
RepairPal Recommendations for Fog Lamp Relay issues
It is recommended that a qualified technician at a trusted repair shop diagnose an issue with faulty fog lamps. Problems can stem from a failing switch, broken wire, loose or corroded ground, dirty or incomplete connection, worn bulbs, or even ECM malfunction, in addition to a bad relay.
What to look out for when dealing with Fog Lamp Relay issues
Care must be exercised whenever working on the electrical system of a car, truck, or SUV. Replacement of a fog lamp relay is simple, but basic safety measures should not be overlooked when diagnosing a faulty fog lamp circuit.
Can I replace the Fog Lamp Relay myself?
The fog lamp relay can be replaced on most vehicles by a person with little DIY experience. The procedure to remove and replace a relay is not very different than that to replace a fuse. However, diagnosis of a lighting system malfunction - whether in the fog lamps or in the headlamps - can be a job that is beyond even someone with more intermediate experience and may require special diagnostic tools, especially if an Electronic Control Module needs to be accessed.
