Turn Signal Flasher: Description and Operation

Fig.5 Combination Flasher:

COMBINATION FLASHER
The combination flasher is located in a dedicated connector receptacle integral to the back of the left multi-function switch housing on the top of the steering column, where it is concealed beneath the upper steering column shroud. The combination flasher is a smart relay that functions as both the turn signal system and the hazard warning system flasher, and is also sometimes referred to as the combo flasher. The combination flasher contains active electronic Integrated Circuitry (IC) elements. This flasher is designed to handle the current flow requirements of the factory-installed lighting. If supplemental lighting is added to the turn signal lamp circuits, such as when towing a trailer with lights, the combination flasher will automatically try to compensate to keep the flash rate the same.

The combination flasher is contained within a rectangular molded plastic housing that is black in color. The combination flasher has five blade-type terminals that connect it to the vehicle electrical system through five matching cavities in the left multi-function switch connector receptacle. While the combination flasher has an International Standards Organization (ISO)-type relay terminal configuration or footprint, the internal circuitry is much different. The combination flasher does not use standard ISO-relay inputs or provide ISO-relay type outputs or functions. The combination flasher should never be substituted for an ISO-relay or replaced with an ISO-relay; otherwise, component and vehicle damage may occur.

The combination flasher cannot be repaired or adjusted and, if faulty or damaged, it must be replaced.

The combination flasher has five blade-type terminals that are intended for the following inputs and outputs: ground, fused B(+), fused ignition switch output (run-acc), turn signal/hazard switch sense, and combination flasher output. Constant battery voltage is supplied to the flasher so that it can perform the hazard warning function, and ignition switched battery voltage is supplied for the turn signal function. The Integrated Circuit (IC) within the combination flasher contains the logic that controls the flasher operation and the flash rate. The IC receives sense ground inputs from the multi-function switch for the hazard flasher, right turn signal, and left turn signal. A special design feature of the combination flasher allows it to "sense" that a turn signal circuit or bulb is not operating, and provide the driver an indication of the condition by flashing the remaining bulbs in the affected circuit at a higher rate (120 flashes-per-minute or higher). Conventional flashers either continue flashing at their typical rate (heavy-duty type), or discontinue flashing the affected circuit entirely (standard-duty type).

Because of the active electronic elements within the combination flasher, it cannot be tested with conventional automotive electrical test equipment. If the combination flasher is believed to be faulty, test the turn signal and hazard warning system. Then replace the combination flasher with a known good unit to confirm system operation. (Refer to ELECTRICAL/LAMPS/LIGHTING - EXTERIOR DIAGNOSIS AND TESTING).