On 4Runner models, the flasher unit is built into the fuse box under the passenger's side. You can tell when the flasher unit works right because it makes a clear, clinking sound while it's active. The presence of any faulty turn signal bulb is suggested when one half of the turn signals stops working, while the unit that activates the blinking doesn't generate an active click sound. There are four possible reasons your turn signals aren't blinking: either you have a burned turn signal fuse under your passenger compartment fuses, a damaged flasher unit, a faulty switch, or loose wire connections. Checking the main fuse box for a bad turn signal fuse should be done first, and then looking for damaged wires is a must before installing a new fuse. To fix the flasher, disconnect it from the fuse box in the passenger area and make sure you put back the exact same model, using the reverse of how you took it out. Gently pull the hazard warning switch from the dash and disconnect it. When the switch is off, measure resistance across terminals 7 and 10 with an ohmmeter. Also, check continuity between terminals 2 and 3 for the lights circuit, and between terminals 5, 6, 9, as well as 7 and 8 for the lights function when the switch is turned on. The hazard warning switch needs to be replaced when it won't turn on.