New answers tagged lights
Problems like this are usually because of a loose ground wire somewhere. Intermittent electrical failures are amongst the hardest problems to diagnose. Without further information (like the make/model/year of the vehicle), it is really hard to help you diagnose this further.
I suggest do not mess with it. Your model may have a smaller capacity alternator and this would upset the whole elctrical system and cause car break down. The foglight can add another 15% load to the system and during occasions the battery is undercharged, it may cause havoc.
Tools Digital Multimiter Voltage, Resistance, continuity settings Automotive specific DMM's are typically the same device but may have a few extra features (Duty Cycle, RPM) CAUTION: Certain modes on the multimeter can cause damage to the device or your car if improperly hooked up. Never connect the DMM to a circuit in parallel when it is on the ampere ...
I'd like to add to Nick's answer and mention a Circuit Tester if you need to simply test the circuit for power.
To track down and troubleshoot electrical issues, you will almost certainly need a multimeter (also known as a Volt-Ohm meter) - digital ones are best, like the one illustrated below (from Wikipedia) You can get cheap ones, which are fine for most automotive stuff, or much more expensive ones with all sorts of clever features. The two most useful things ...
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