Have a friend turn the key to “Start” while you watch the multimeter. If the solenoid clicks but the voltage drops to 9 volts or lower, your battery is too weak to party. But if the voltage stays above 10 volts and nothing else happens, the solenoid is guilty.
Testing A Starter Solenoid With A Multimeter | Detroit Chinatown
Here’s the surprising part: the solenoid also has a smaller trigger wire (usually a thin purple or yellow wire). That wire gets 12 volts only when you turn the key. Touch your red probe to that trigger terminal while a friend cranks it.
If you don’t see 12 volts there when they turn the key, your ignition switch is lying to you. Now the solenoid is innocent, and you need to fix the wiring—or buy your friend a coffee for helping.
Step 3: The Resistance Check (The Sherlock Holmes Move)
Turn off the car, disconnect the battery (safety first—sparks are for fireworks, not for you), and set your multimeter to ohms (the symbol that looks like a horseshoe). Touch the probes to the solenoid’s two large terminals.
A good solenoid will show less than 1 ohm—basically zero resistance, like a greased pig sliding through a pipe. If you see infinite resistance (an “OL” on the screen), the internal contacts are fried, and the solenoid is dead as a doornail.
Fun fact: A solenoid’s coil has about 5–10 ohms of resistance. You can check that by probing the small trigger terminal and one large terminal. If it’s open (OL), the coil is broken, and your car will never start again until you replace it. Dramatic? Yes. True? Also yes.
Testing A Starter Solenoid With A Multimeter | Detroit Chinatown
