How can you check if a resister is bad
I use the ohmmeter function on my digital multimeter (DMM). You can get a basic DMM from Sears or Radio Shack for about $30.
First, (safety check) measure the voltage across the terminals unless you know there is no power in the circuit, or better yet, disconnect the resistor so other components don't give you a false reading. Attempting to read the value of a resistor in a live circuit will give you a meaningless number at best, and may severely damage your meter at worst. It could also damage other parts in the circuit.
Now switch your meter to the lowest ? range (Greek capital Omega, for Ohm) greater than the expected value of the resistor. Connect one test lead to each end of the resistor. The number you read should be the expected value plus or minus the tolerance (e. g., a 100 ? 5% resistor should read somewhere between 95.0 - 105.0 on the 200 ? range.). A bad resistor will usually show up as 1___ (over-range) because it will be burned out and open. Some very old carbon composition resistors will short (read much less than 1 ?) when they fail.
Often, a visual inspection will identify a bad resistor - if you can see that it's burned and broken, it's bad and further testing is unnecessary. The ohmmeter is for all the other cases.
Nov 19, 2010 |
2005 Dodge Caravan