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 | + | 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. |
==Overview== | ==Overview== | ||
| − | The turn signal system is a | + | 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. | + | 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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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. | 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 | + | 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 | + | 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. 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). | 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 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 | + | 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 in a new flasher. 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. | 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. | ||
| − | 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. |
| − | The | + | The typical causes of this type of failure are exceeding the lamp count, exceeding the recommended wattage of the bulbs, install the wrong bulb in the system (ie: a single element bulb, instead of a dual), shorting of the lamp system (common culprit: trailer plugs), and the addition of extra lamps (such as a trailer) in the circuit without upgrading the flash unit. |
| − | + | To prevent this malady from occurring, always install the recommended wattage or bulb number when replacing the bulbs. | |
| + | The net result usually is a very rapid flash rate. And in some cases, failure of the flasher unit, or premature failures on subsequent units. | ||
| − | The | + | ==The turn signal switch== |
| + | This little switch has been responsible for more "hair pulling” incidents than most other parts of the vehicle. When you understand how t works, and why it works the way it does, it’s really quite simple. | ||
| − | + | At the bottom of the steering column on traditional turn signal systems, there is a plug. From that plug all the system signals (power) go in and come out. And, an added system, a wire from the brake lamp switch. | |
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| − | + | At this plug you will find flash unit power in to the switch handle, two sets of wires for the left and right turn signal lamp socket power, Those will be front left, rear left, front right, and rear right. These wires bring power to the lamps for turn signal AND brake lamps to the rear. Also at that plug you will find a wire for the brake lamp system from the Brake lamp switch. | |
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| − | At this plug you will find | + | |
The switch itself, Located below the horn ring on most traditional Systems, is like any other, except...It is two switches in one, the Left side and Right side. It also provides the isolation required between the Brake lamp system and the turn signal system. | The switch itself, Located below the horn ring on most traditional Systems, is like any other, except...It is two switches in one, the Left side and Right side. It also provides the isolation required between the Brake lamp system and the turn signal system. | ||
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