If you own an older Chevy pickup truck, chances are you've experienced some problems with the turn signals at some point. The wiring for the turn signals on these old trucks tends to degrade over time, leading to issues like fast blinking, hyperflashing, or turn signals not working at all. While you could take it to a professional mechanic, with some basic tools and DIY know-how, I can show you how to troubleshoot and fix these common turn signal wiring problems yourself without too much hassle.
Understanding the Turn Signal Wiring
To fix any electrical issue, you first need to understand how the system works when operating correctly. Here's a quick rundown of how the turn signal circuit functions on a classic Chevy pickup:
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Power comes from the fuse box to the turn signal flasher unit. This acts like a switch to pulse power to the turn signal bulbs.
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From the flasher, power branches off to the front and rear turn signal bulbs on each side.
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A ground completes the circuit when the turn signal or hazard switch is activated.
The main components are the bulbs, flasher unit, switch, and wiring between them. If any of these aren't working properly, it can cause problems.
Key Signs of a Turn Signal Wiring Problem
How do you know if you have a turn signal wiring issue? Here are some common symptoms:
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Fast blinking - When a bulb is burnt out, the flasher will blink rapidly because the circuit doesn't have full load.
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No blinking at all - If the flasher or switch isn't working, the signals won't activate.
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Hyperflashing - When using LED bulbs, the lower load can cause the flasher to blink too quickly.
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Intermittent operation - Corroded connections or damaged wires can cause inconsistent function.
If you notice any of these, it likely indicates a wiring problem. Don't ignore it, as damaged wiring can lead to total failure.
Inspecting the Bulbs and Sockets
The first thing I do when troubleshooting turn signal problems is visually inspect all the bulbs and sockets. Here are some tips:
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Check that the correct bulb type is installed in each socket. Using LED or the wrong wattage incandescent bulbs can cause issues.
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Look for any bulbs that appear dark or burnt out. Burnt out bulbs are the most common cause of fast blinking.
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Wiggle the bulbs gently to check for loose, corroded connections. Clear away any dirt or oxidation.
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Ensure the ground pins on the sockets make solid contact with the vehicle body.
Replacing any burnt out or improper bulbs is quick and cheap, and can potentially fix your turn signal issues.
Testing the Flasher Unit
The next component to check is the turn signal flasher. This acts like a relay to make the turn signals blink on and off.
To test the flasher:
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Locate it under the dash - it looks like a small cylindrical relay.
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With the key on, jumper wires across the two terminals on the flasher.
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If it's working, the unit will make a buzzing sound and the jumpered wires will have power pulses.
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If nothing happens, the flasher is likely bad and needs replacement. They cost around $10-15.
Tip: A fast turn signal blink rate can sometimes be fixed by swapping to a heavy duty flasher designed for LED bulbs.
Checking Wiring Condition and Connections
With the bulbs and flasher checked, the next step is to inspect the condition of the wiring itself. Here's what I look for:
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Any cracking, chafing, or corrosion on the turn signal wiring. Damage can cause shorts or open circuits.
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Make sure wiring connectors are fully plugged in at the flasher, switch, and all light sockets. Wiggle test for looseness.
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Check for securely grounded connections. Remove paint or rust from ground points.
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Use a multimeter to test for continuity between sockets and switches. Breaks in continuity signal a bad wire section.
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Carefully follow each wire run looking for potential damage. Re-wrap any exposed sections with electrical tape.
Repairing or splicing any damaged wiring sections may be needed to restore proper function.
Troubleshooting the Turn Signal Switch
The turn signal switch activates the flasher to send power to the bulbs. If your signals don't work at all, the switch could be faulty.
To troubleshoot the switch:
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With key on, check for power at the switch wiring plug using a test light or multimeter. No power indicates an upstream issue.
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Manual activate the switch signals and hazard mode. If nothing happens at the bulbs, the switch contacts could be damaged.
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Tap the switch with the heel of your hand to see if impact gets the signals working. Loose internal parts can cause intermittent operation.
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Turn the wheel left and right while activating the signals. If they cut in and out, the cancelling mechanism inside the switch may be faulty.
If you confirm the switch is defective through testing, replacement units are readily available online or at auto parts stores for around $20-40.
When All Else Fails, Trace and Re-Run the Wiring
If you've methodically tested all the bulbs, sockets, flasher, wiring, and switch but are still experiencing turn signal problems, there could be an unseen break or short in the wiring that was missed. At that point it may be necessary to trace and re-run new wiring for the entire turn signal circuit. Here's an overview:
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Draw a wiring diagram of the existing turn signal circuit to use as a reference.
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Starting at the flasher, carefully follow the full circuit from power source to switch to bulbs testing continuity.
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Where any faults are found, run a new wire segment keeping everything neatly bundled.
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Use butt connectors or solder for inline splices. Use heat shrink over connections.
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Avoid routing new wiring close to hot or moving components that could cause damage.
While re-wiring the full turn signal circuit is labor intensive, it should resolve any lingering electrical gremlins once and for all. Just take it slow and be mindful.
Conclusion: Patience and Dedication Pays Off
Troubleshooting electrical problems requires diligence and understanding, but anyone with basic skills can learn to fix common turn signal wiring issues on old Chevy pickups. The place to start is methodically testing bulbs, sockets, flasher, switch, and wiring one-by-one until the fault is discovered. Don't get discouraged - with some patience and dedication, you can get those trusty signals blinking properly again without an expensive shop visit.
Let me know in the comments if you have any other tips for diagnosing turn signal problems on a classic Chevy pickup! I'm always looking to learn more handy repair advice.