How do turn signals work?
m (How Do My Turnsignals work? moved to How do turn signals work?) |
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| − | - | + | Turn signals are one of the most misunderstood sub-systems in most vehicles today. They really are simple when you stop and think about HOW the system performs its job, and why it is wired the way it is. Most commonly, the system is mis-wired and interacts with the brake lamp system causing non functioning turn-signals under braking conditions. And, 4-way flashing action when not in braking mode. |
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| + | ==Overview== | ||
| + | The turn signal system is a System that is isolated from other lamp circuits, but appears to function with the Brake lamp system, which, in part is true... | ||
| − | + | The turn signal on a traditional system is a shared element with the brake lamp function at the bulb to the rear of the vehicle. The most common misconception is "I can wire my turn signals and brake lamps together at the light housing and it will be fine...and that's where the trouble begins. | |
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| − | + | ==Power feed and flash unit== | |
| + | Power on a traditional flash unit is delivered to the system via the flash unit. A fused, switched lead is run from the fuse buss to the flasher, so that it only receives power in the "Hot in Run" position. | ||
| − | + | From the flasher, a wire is run to the center wiper (or moveable contact) of the turn signal switch inside the steering column. | |
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| − | + | The flasher operates from internal heat on a tungsten bi-metallic "strip" that makes or breaks the contact at the switch side of the contact, or power output side. | |
| − | + | As the system lamp load is imposed on the flasher unit, the bimetallic strip heats up, and curls up...breaking contact to the switch... It then cools down very rapidly, and makes contact again, the lamp load again heats the strip and it opens up. Thus: flash. | |
| − | + | When the load is under-matched to the flash unit (bulb(s) burned out), the flash cycle is slowed or stuck "On”. This is what we perceive as a lamp outage and when this occurs. We pull over and have a new bulb put in. | |
| − | + | This occurs because the lamp load on the bimetallic strip inside the flasher unit has been reduced to a point where the time allotted for heat is extended (slowing the flash rate), or never reaches the heat point of the strip (turning on and staying on). | |
| − | When the load | + | When these flash units fail, it's usually because the load on the strip has exceeded its capability to recover, and the strip just melts, leaving the switch contact side "Open” from power. This is when we normally put a new flasher in. Causes of this type of failure can include age of the flash unit, overtaxing of the lamp load (as in trailer lamps), or a short within the electrical system. |
| − | + | The other side of the coin is too many bulbs within the lamp load circuit, which taxes the flasher unit. This causes the bimetallic tungsten strip to heat and cool at a very rapid rate. | |
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| − | The other side of the | + | |
The more current draw THROUGH the flasher unit the faster it opens and closes the contact... | The more current draw THROUGH the flasher unit the faster it opens and closes the contact... | ||
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