Circuit Inoperable

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Symptom—Driver-side reverse light not working, 

Since one of the lights is working, we know that overall the circuit is working properly. This means that there is an open circuit between the wiring and the non-working bulb. Possible causes are:

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• A bad bulb.

• A bad connection between the bulb and the bulb socket.

• A bad connection between the connector and the bulb socket.

• A bad connection somewhere in the wiring harness to this connector.

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Circuit Works, but Blows Fuses

 

• Another more obvious case where a circuit works but blows the fuse is where some kind of aftermarket electronics has been added to an existing circuit and its current requirements, combined with the current requirements of the accessory(s) already connected to said circuit, exceeded the circuit’s capability.

• This is where folks are tempted to replace said fuse with a larger value fuse. In the example I gave, the gauge of wire, relay, and fuse were all selected based on the fans’ current requirements, so this circuit is in harmony.

• This is exactly what the OEM does for every circuit in every vehicle they build. In such a case, the solution is to connect the aftermarket accessory to a different source of power.

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Wiring is Burned Up

 

This is hopefully not something you’ve experienced recently. I’ve seen it happen many times over the years and it is typically caused by one of three things:

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• Gauge of wiring insufficient for current demands of the circuit—as I just discussed.

• Wiring not fused/fused improperly, and pinched or shorted—this causes a short circuit, which causes an extremely high amount of current to flow through the wire, which results in the insulation being burned right off of it.

• A high resistance connection with high current flowing through it, such as a connector termination.

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 Battery is Drained Overnight

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• Symptom—Battery is dead after sitting for longer than 96 hours

• I have a suspicion about what the problem is, but let’s go through the motions. This vehicle has a bunch of aftermarket electronics, so it’s a great candidate to separate them and find the problem.

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Intermittent Circuit Operation

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These kinds of problems can be the most frustrating of all. Sometimes the accessory works, sometimes it doesn’t, with no rhyme or reason. Worst of all, Murphy’s Law ensures that it always works when you take it in for someone to look at it.