If you find a point of high resistance (over five ohms), you will need to attach a bonding strap or wire between the panels or parts where resistance is highest. Continue to where the fender attaches to the main body, and from there to the accessory. Starting at the battery, run the voltmeter probe from the battery to the first grounding point, usually a fender on muscle cars and trucks. If the reading is higher, you need to probe the grounding path between the accessory and the battery. If you find a point where voltage is present, then you need to add a bonding strap or find a new grounding point so no voltage is present at any of the grounding points. Turn the accessory on and retrace the grounding path as you did before. If the resistance is okay but the accessory still isn’t working right, set the voltmeter to DC current (voltage). If you have a reading less than five ohms, the ground is okay.

Set the voltmeter to read ohms (resistance) and probe the battery’s negative stud and ground connection on the accessory (the ground terminal on an amp, for example). If your accessory still doesn’t work properly after redoing the grounds, you will need a voltmeter or multimeter to trace the wiring. Using a Voltmeter/Multimeter to Test the Connection If you are grounding an accessory to the engine, it’s good practice to run a ground wire directly to the alternator case and make sure there is no paint between the starter and the engine block mounting surface. Best Practice for Grounding Accessories to an Engine

Paint on body panels and the engine acts as an insulator, resulting in a bad ground connection. You must make sure the ground wire is attached at a point that is free of paint, rust, or plating. Many think that as long as the accessory’s ground wire is touching some part of the vehicle, it is grounded. Make Sure You Have a Quality Ground Point A bad ground can cause noise in an audio system, make electric fuel pumps run hot or produce low pressure, and make electronic engine controls do weird things. Chasing down electrical gremlins in a motor vehicle can be an exercise in frustration-the kind of frustration that makes young men old and old men talk to themselves.Īn electrical problem can often be traced to a single source: a bad ground connection.

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