How do turn signals work?
From Crankshaft Coalition Wiki
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==Overview== | ==Overview== | ||
Turn signals are one of the most misunderstood sub-systems in 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. The following procedures will cover most of the basic and common problems found in the turn signal system. | Turn signals are one of the most misunderstood sub-systems in 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. The following procedures will cover most of the basic and common problems found in the turn signal system. | ||
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==Problems== | ==Problems== | ||
Most commonly, problems occur when the system is wired incorrectly or bulbs are inserted into worn sockets upside down. This can cause malfunctioning of the brake lamp system, turn signals, 4-way emergency flashers, and brake lights (among other things). | Most commonly, problems occur when the system is wired incorrectly or bulbs are inserted into worn sockets upside down. This can cause malfunctioning of the brake lamp system, turn signals, 4-way emergency flashers, and brake lights (among other things). | ||
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The turn signal system is isolated from other lamp circuits, but appears to function with the brake lamp system, which, in part, is true. | The turn signal system 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." That's typically 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." That's typically where the trouble begins. | ||
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| + | The turn signal shares the ground with the park light in the front of the vehicle. If the ground is loose or not connected, it can allow voltage to back feed from the park lights to the turn indicator. | ||
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| + | If you have LED lights on the vehicle, you often will need 1K ohm pull-down resistors on left and right turn to | ||
| + | bleed off residual voltage. Check with a digital volt meter, look for 3 volts or more still sitting on the turn | ||
| + | signal wire. Another possibility is if they don’t have a good ground, the PARK and TURN bulb filaments | ||
| + | are both tied together and go to body ground like a “Y”. If this ground wire is not connected, the park | ||
| + | light can back-feed to the turn signal circuit. If you use LED lights for your turns/brakes, you | ||
| + | either need load balancers to draw enough current for the flasher to work or you should use | ||
| + | a No Load Flasher. | ||
==Power feed and flasher unit== | ==Power feed and flasher unit== | ||
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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 net result usually is a very rapid flash rate. And, in some cases, failure of the flasher unit, or premature failures on subsequent units. | ||
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| + | CORRECT FLASHER CONNECTIONS: | ||
| + | The flasher normally will have two terminals: X = incoming power L = Load / lights | ||
| + | No-load flashers will have a 3rd connection for ground. | ||
| + | If X & L are swapped, the flasher wont operate properly when LED lights are installed but regular bulbs would not be affected and would seem to work normal. | ||
==The turn signal switch== | ==The turn signal switch== | ||
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This is how the two systems are isolated. This is the most problematic issue for a novice to understand, primarily because nobody ever took the time to explain it to them in any detail. | This is how the two systems are isolated. This is the most problematic issue for a novice to understand, primarily because nobody ever took the time to explain it to them in any detail. | ||
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==Turn signal system troubleshooting== | ==Turn signal system troubleshooting== | ||
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#If it reads infinite, it is open. Replace the fuse and test the signal system again. If it reads 000, it is good, put it back in the buss box. | #If it reads infinite, it is open. Replace the fuse and test the signal system again. If it reads 000, it is good, put it back in the buss box. | ||
#Next, set your meter to DCV, V X 50 or auto range, turn the key on, and remove the flasher. Place the black probe on ground, the the other into either of the two flasher terminals. One will read infinite, the other should read 12 volts. If you have that, power is good to the flash unit. | #Next, set your meter to DCV, V X 50 or auto range, turn the key on, and remove the flasher. Place the black probe on ground, the the other into either of the two flasher terminals. One will read infinite, the other should read 12 volts. If you have that, power is good to the flash unit. | ||
| − | #Next, set your meter to ohms, RX1 scale and measure across | + | #Next, set your meter to ohms, RX1 scale and measure across the pins or wires. Repair or replace as required. |
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#If you don't have either a cut condition, or a burned socket, and still dead, check any lead front, or rear of the selected side. It should have 12 volts, either steady or intermittent on it. If not, your trouble is in the column harness between the plug and the switch. Or, the switch itself is bad. Repair or replace as required. | #If you don't have either a cut condition, or a burned socket, and still dead, check any lead front, or rear of the selected side. It should have 12 volts, either steady or intermittent on it. If not, your trouble is in the column harness between the plug and the switch. Or, the switch itself is bad. Repair or replace as required. | ||
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===Front signals work, but rear signals are dead (or vice-versa)=== | ===Front signals work, but rear signals are dead (or vice-versa)=== | ||
| − | #Isolate the two wires on the effected end from the column plug. Using your voltmeter, set to the above parameters, select a side, and measure the wire from the plug. It should show 12 volts (solid or intermittent). If | + | #Isolate the two wires on the effected end from the column plug. Using your voltmeter, set to the above parameters, select a side, and measure the wire from the plug. It should show 12 volts (solid or intermittent). If the socket ground and a known good ground. If it shows 12 volts, you may have an open ground wire. Replace or install a ground from each socket to a hard frame ground, following proper bonding procedures (star washers and burnishing). |
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===Left or right side turn signals dead=== | ===Left or right side turn signals dead=== | ||
Follow the same procedure as outlined for front or rear dead above. However, apply it to the affected side. | Follow the same procedure as outlined for front or rear dead above. However, apply it to the affected side. | ||
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===All rear turn signals flashing=== | ===All rear turn signals flashing=== | ||
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[[Category:Electrical]] | [[Category:Electrical]] | ||
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