ATG (JulAug12) - Testing Voltage

By Editor,

QUESTION: Roger what do you mean when you say “check voltage across the solenoid”? Voltage across battery? This confuses me..VA from NE

ANSWER: Sorry to confuse you and all this means is just what I am implying. You are literally testing voltage across a given point. Example is the solenoid. Typically you have four connection points. Two connections are for activation (primary) and two are for power circuit (secondary). So when I say I want you to check across the activation terminals (small terminals) I mean connect the black voltmeter wire lead to the small terminal negative input. Connect the red voltmeter lead to the small solenoid positive terminal. Meaning across the two terminals.

Why we do this is to see if we have both potentials present at the time of solenoid activation. If both potentials are present and the solenoid does not “click” the solenoid coil is open (replace solenoid). It is just that simple. If we do not read both potentials we are missing one and we have to find out which one is missing. At the same time you will not connect across the secondary (power circuit) as that will be a like potential (usually positive). So talking about “across” means a component that has two potentials present not one. A battery has two potentials, solenoid, light, coil, relay, horn, converter, and so on.


Connecting to just one terminal is checking only one potential. Meaning you have to find the other potential somewhere else such as battery negative or battery positive.



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