Fog Light Switch Replacement Cost Estimate

To diagnose a bad fog lamp switch, 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 may check the relay to make sure it is operational and that there is voltage to the relay. The wires to the switch will also be checked to make sure it is getting voltage. If voltage is present at the switch, the technician will test the switch for continuity - whether or not it is capable of transmitting electrical current when operated - and possibly bypass the switch to see if the relay will turn the lamps on. If the switch has power but will not operate, the switch is likely to be defective. In some cases, the problem might originate in the body control module or lighting control module. In these cases, the technician will look for a diagnostic trouble code (a fault code) that can be read with a scan tool.

To replace a bad fog lamp switch, a technician will disconnect power to the switch (usually by removing the fuse or disconnecting the battery) and carefully remove the dashboard trim panel that houses the switch assembly. The switch is unplugged from the wire harness connector and disassembled from the trim panel. The new switch is installed in its place, plugged in, and returned to the dashboard before the fuse is replaced and the system tested. On vehicles where the switch is located on an arm connected to the steering column, disassembly of the steering column trim will be necessary for access. The arm will likely contain switches that control multiple vehicle functions and the whole module will need to be replaced.

We recommend thorough and proper diagnosis of the fog lamp issue prior to purchasing replacement parts for the vehicle. If not, properly functioning components can be replaced erroneously. Also, wiring around the switch is not advised as a means of bypassing a faulty switch or relay. Homemade switches can lead to vehicle fires or electric shock.

The dashboard trim can be tricky to remove without damaging the panels. On some higher-end vehicles, the trim components can be extremely expensive to replace, and, in some cases, can only be replaced as a complete set costing thousands of dollars. Care should be exercised when disassembling components on the dashboard.

In many cases, the fog lamp switch can be replaced by a person with intermediate DIY experience as long as the problem has been properly diagnosed and the switch is easily accessible. Special tools may be required on some vehicles to avoid damage to the dashboard and trim panels. If the switch is mounted on the steering column, the procedure will likely be more complex and may best be left to a repair professional who understands how to disassemble a steering column.