How do turn signals work?
m (Unprotected "How do turn signals work?") |
(Small clean up, format.) |
||
| Line 1: | Line 1: | ||
{{youcanedit}} | {{youcanedit}} | ||
| − | 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. Most commonly, the system is | + | ==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. | ||
| + | |||
| + | ==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). | ||
| − | |||
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. | ||
| Line 9: | Line 12: | ||
| − | ==Power feed and | + | ==Power feed and flasher unit== |
| − | Power on a traditional | + | Power on a traditional turn signal flasher unit is delivered to the system via the flasher 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 movable contact) of the turn signal switch inside the steering column. | From the flasher, a wire is run to the center wiper (or movable contact) of the turn signal switch inside the steering column. | ||
| Line 21: | Line 24: | ||
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 " | + | 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 or distorts, 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. | ||
| Line 31: | Line 34: | ||
*Exceeding the lamp count. | *Exceeding the lamp count. | ||
*Exceeding the recommended wattage of the bulbs. | *Exceeding the recommended wattage of the bulbs. | ||
| − | *Installing the wrong bulb in the system ( | + | *Installing the wrong bulb in the system (i.e.: a single element bulb, instead of a dual). |
*Shorting of the lamp system (common culprit: trailer plugs). | *Shorting of the lamp system (common culprit: trailer plugs). | ||
*The addition of extra lamps (such as a trailer) in the circuit, without upgrading the flash unit. | *The addition of extra lamps (such as a trailer) in the circuit, without upgrading the flash unit. | ||
| Line 78: | Line 81: | ||
The exact same wiring is true for the right side, with one exception: the brake lamp power is picked up from the left contact (daisy chained). | The exact same wiring is true for the right side, with one exception: the brake lamp power is picked up from the left contact (daisy chained). | ||
| − | == | + | ==Function== |
In review, the system works in the following manner. | In review, the system works in the following manner. | ||
| Line 93: | Line 96: | ||
===Single lamp failures=== | ===Single lamp failures=== | ||
| + | This is one of the most common failures found on vehicle lamp systems. The first thing to do is check the bulb. If the bulb is good, check for power at the socket. | ||
| − | + | ====How to check for power at the socket:==== | |
| − | + | ||
#Get your DVOM out, set it for volts scale, V X 50 or higher, and turn the key on then the offending signal. | #Get your DVOM out, set it for volts scale, V X 50 or higher, and turn the key on then the offending signal. | ||
#Carefully insert the probe of your meter into the socket, to the contact pad (S) on the bottom of the socket, and the other to a good ground. | #Carefully insert the probe of your meter into the socket, to the contact pad (S) on the bottom of the socket, and the other to a good ground. | ||
| Line 110: | Line 113: | ||
===Dead system=== | ===Dead system=== | ||
| − | |||
If none of the turn signal functions work at all, follow the steps below. | If none of the turn signal functions work at all, follow the steps below. | ||
| Line 134: | Line 136: | ||
Inspect the turn signal switch for a short between the brake lamp circuit and the signal circuit. Check the column plug and harness for shorts. Ohm the harness out with no power on, but either side selected. You should have no reading from the selected side to the brake lamp circuit, and continuity in the "Off" position to the brake lamps. If not, inspect the switch and harness, and repair or replace as needed. | Inspect the turn signal switch for a short between the brake lamp circuit and the signal circuit. Check the column plug and harness for shorts. Ohm the harness out with no power on, but either side selected. You should have no reading from the selected side to the brake lamp circuit, and continuity in the "Off" position to the brake lamps. If not, inspect the switch and harness, and repair or replace as needed. | ||
| − | == | + | ==Tools, materials, and equipment== |
| − | + | ||
| − | + | ||
| − | + | ||
*[[Digital Volt-Ohm Meter]] | *[[Digital Volt-Ohm Meter]] | ||
*[[Jumper wire set]] | *[[Jumper wire set]] | ||
Your Privacy Choices