GM 25721611 Flasher Assembly, Hazard Lamp & Turn Signal Lamp

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1999 DeVilles used to control turn signals and hazard flashers by means of two separate flasher units placed under the dash board close to the steering column and left kick-panel. In 2000 through 2005 DeVilles and all Sevilles, both the flashers were merged into one unit placed below the dash also near the steering column. For all cars made in 2006 onwards however, a turn signal relay is not employed since their functions are controlled by BCM which generates a positive or negative output voltage in response to left or right turn signal multi function switch respectively. In normal working condition, it produces an audible click while operating. An early model with missing sound of clicking at the flasher unit when either side of its turn signals fail (early models) or a latter mode where one side of the car flashes faster than another on that same side yet fails completely (latest models) may have faulty blinkers. When both turn signals refuse to blink, it could mean a fuse has blown; the switch is broken; there is no flasher unit; or there is no closed connection in between them. If upon inspection of the fuse box you realize that the turn signal fuse has blown out you should search for a short circuit before putting in another one. The left knee bolster should be removed and if necessary, close out panel before disconnecting electrical connectors from (later models turn signal/hazard flasher located under the lest side of the steering column). The spare should be exactly like it. Check for any variations between new piece and old one prior to installation. Reversing of steps applies during installation.

To examine continuity through the relay control coil, follow the polarity indicated in the illustration during testing and reverse the ohmmeter leads to check continuity in the other direction. A relay with a resistor should yield consistent resistance values in both directions, while a diode should exhibit higher resistance in the forward polarity direction.