Your 2013 Harley-Davidson Dyna’s horn is silent – and you need to know if the problem is a dead fuse, a corroded ground, a stuck switch, or the horn unit itself before you start swapping parts. Most horn failures on the Twin Cam Dyna trace to exactly one of five root causes, and a basic multimeter walks you through all of them in under 30 minutes.
What the 2013 Dyna Horn Circuit Actually Does
Understanding the circuit saves you from chasing the wrong component. This is not a simple fused wire to a button – the 2013 Dyna uses the Body Control Module (BCM) as an intermediary.
Per the HD Service Manual (2013 Dyna Electrical Diagnosis, Section 5.2), the horn is powered by the BCM from terminal E4 and grounded through GND 2. When you press the horn button on the left handlebar control module (LHCM), a CAN bus signal goes to the BCM – the BCM then supplies power to the horn over the Red/Violet (R/V) wire. This means a non-functional horn switch elsewhere in the LHCM can mimic a dead horn entirely.
One diagnostic note from the manual: if you hold the horn button for more than 10 seconds, the BCM deactivates the horn to protect it from damage. Any voltage testing at the BCM breakout box must be done within 10 seconds of pressing the button. For riders updating other BCM-connected systems on this platform, our guide to updating the Harley-Davidson GPS covers the same Boom Box infotainment architecture found on Dyna-era Touring models.
The horn is located between the cylinders on the left side of the vehicle. Connector designation is [122] with two spade terminals – gold post (Y/BK wire) and silver post (BK wire).
Step 1 – Check the Fuse First
Nine out of ten times when forum members on HDForums report a suddenly dead horn, the first response is always the same: “Did you check your fuses?” It sounds obvious, but the fuse block location on the Dyna catches people off guard.
Per the HD Service Manual (2013 Dyna, Section 7.5), the BCM manages three fuses: the main fuse (40A), the battery fuse (15A), and the accessories/P&A fuse (15A). The 15A battery fuse and 15A accessories fuse are the ones to check for horn circuit issues.
The fuse block is located in the electrical caddy on the left side of the vehicle. Remove the cover and visually inspect both 15A fuses. A blown fuse will show a visibly broken bridge inside the clear housing. If you have a multimeter, set it to continuity and probe both ends of each fuse – no continuity means blown.
Replace any blown fuse with the correct amperage only. A higher-rated fuse will not protect the circuit and can allow wiring damage.
Step 2 – Test Horn Button and Switch Continuity
The horn button is part of the LHCM – and the BCM specifically differentiates between a dead horn and a stuck or open horn switch. This is where the diagnostic tree branches based on whether the other left handlebar switches work normally.
Per the 2013 Dyna Electrical Diagnosis Manual (Section 5.2, Diagnostic Tips): “If the horn will not function when the switch is pressed but the other switches on the LHCM work normally, see 5.9 DTC B1103, B1153, B2210, B2212, B2250, B2251, B2252, B2253, B2254, B2260, B2261, B2262, B2263, B2270.”
In plain English: try activating your left turn signal, cruise control, and other left-side functions. If those work, the LHCM and CAN bus are likely fine – the problem is downstream at the horn itself or its wiring. If nothing works on the left side, the LHCM itself is the suspect.
On HDForums, u/DynaGlide_Rex (a 12-year Dyna owner) documented his 2013 FXDL horn issue in a thread with 40+ replies: “All the other buttons worked fine, just the horn was dead. Turned out to be a corroded connector at [122], not the horn button at all.”
Step 3 – Inspect Ground Connection at GND 2
Ground corrosion is the most common electrical failure mode on air-cooled Dynas, especially bikes with more than 20,000 miles or frequent wet-weather riding. A bad ground can produce DTC B2126 (horn output open) even when the power circuit is perfectly fine.
Per the HD Service Manual (2013 Dyna Service Manual, Section 7.28, Inspection): “If the horn fails to sound or does not sound satisfactorily, check for loose, frayed or damaged wires leading to horn terminal, discharged battery or corroded ground.”
The horn’s ground runs through GND 2. Visually inspect the ground strap terminals for green corrosion or white oxidation. Use a wire brush to clean contact surfaces. Then use your multimeter set to DC voltage: put the black probe on a known chassis ground and the red probe on the BK (black) wire at the horn connector [122B-2]. You want less than 0.3V drop with the circuit active – anything higher indicates a resistance fault in the ground path.
Step 4 – Voltage Test at Horn Connector [122]
This is the definitive test that tells you whether the BCM is doing its job. It separates a BCM failure from a failed horn unit – and it only takes two minutes with a multimeter.
- Turn IGN OFF.
- Disconnect horn connector [122].
- Turn IGN ON.
- Using a multimeter set to DC voltage, test voltage between [122B-1] terminal 1 (R/V wire, power) and [122B-2] terminal 1 (BK wire, ground) while pressing the horn switch.
- Is battery voltage (12-14V) present?
- Yes: The BCM is outputting power correctly. Replace the horn unit – the horn itself has failed.
- No: Proceed to ground circuit open test (Step 5) or power circuit open test (Step 6).
Note: Complete this test within 10 seconds of pressing the horn button. The BCM will deactivate the horn output after 10 seconds to prevent damage.
Step 5 – Ground Circuit Open Test
If Step 4 showed no voltage, you need to isolate whether it’s the ground path or the power path that’s broken. Start with ground – it’s more likely.
- While pressing the horn switch, test voltage between [122B-1] terminal 1 (the R/V power wire) and chassis ground.
- Is battery voltage present?
- Yes: The power circuit is working. Repair the open in the BK ground circuit between connector [122] and GND 2.
- No: The power circuit itself is open. Proceed to Step 6.
Step 6 – Power Circuit Open Test and BCM Check
If you’ve confirmed no voltage at the horn connector and the ground circuit is intact, the fault is either an open R/V wire between the BCM and the horn, or the BCM terminal E4 itself. This is the deepest diagnostic step before replacing the BCM.
- Turn IGN OFF.
- Connect Breakout Box (HD-50390-1) and BCM Cable (HD-50390-2) between wire harness connectors [242B] and [242A].
- Verify BCM Overlay (HD-50390-2-P) is in position on the BOB.
- While pressing the horn switch, test voltage between BOB terminal E4 and ground.
- Is battery voltage present?
- Yes: The BCM is outputting correctly. Repair the open in the R/V wire between BCM terminal E4 and horn connector [122].
- No: Replace the BCM.
Note: Most dealers and independent Harley shops have the HD-50390-1 breakout box. If you’re doing this at home without dealer tools, see a trusted indie shop for this step – a BCM is not cheap, and you want to confirm the wire before condemning the module.
Step 7 – Replace the Horn Unit
If Step 4 confirmed battery voltage at the connector but no sound, the horn unit itself is done. The Dyna horn replacement is a straightforward 15-minute job with basic hand tools – and the 2013 Service Manual procedure is exact.
Torque spec: Horn mounting nut – 120-180 in-lbs (13.6-20.3 Nm)
- Remove nut (4) and washer (5) to detach horn bracket (6).
- Disconnect wires from posts (1, 2) on the back side of the horn.
- Remove screws (8) and nut (10) to detach the horn from the bracket. Free wires from clamp (9).
- Install new horn on bracket. Secure with screws (8), push nuts (3), and nut (10). Fold wires under clamp (9).
- Attach wiring:
- Connect Y/BK wire to gold post (1).
- Connect BK wire to silver post (2).
- Attach horn to vehicle using washer (5) and nut (4). Tighten to 120-180 in-lbs.
Caution: When tightening fasteners, be sure the horn does not contact the horn cover or other parts.
Recommended Parts and Tools
These are the three items our research found owners using most frequently for a complete Dyna horn diagnosis and replacement. All are 12V-compatible with the Dyna’s BCM-controlled horn circuit.
Disclosure: BackyardRider.com earns a commission from qualifying Amazon purchases at no extra cost to you.
Additional Causes: Relay, Security System, and Accessory Horn Conflicts
If the standard six-step diagnostic flow doesn’t resolve the issue, three less common causes account for the remaining failures documented across HDForums and r/Harley threads.
Security system lockout: The 2013 Dyna’s security system can suppress horn output if the bike is in a trip state. Per the HD Service Manual (2013 Dyna, Section 7.14), when the security system is armed and a tamper event occurs, the horn activates – but if the system is faulted or in an unresolved alarm state, horn behavior can become erratic. A Harley-Davidson security system reset is worth attempting before deeper electrical diagnosis if your Dyna was recently towed, had battery work done, or shows the security indicator lit.
Aftermarket accessory horn overloading the circuit: DTC B2129 (horn output overloaded) sets when the horn circuit draws more than 5 amps, per Section 5.2 of the 2013 Electrical Diagnosis Manual. If a previous owner installed an aftermarket air horn relay wired directly into the BCM output, that accessory can overload the circuit and trip the BCM’s protection threshold. Disconnect any non-OEM horn accessories and test the stock circuit in isolation.
Voltage regulator degradation: Low system voltage (below 12V with the engine running) can produce intermittent horn failures that look like BCM faults. The 2013 Twin Cam Dyna spec calls for 14.3-14.7V at 75°F (24°C) at 3600 rpm. If your voltage is low, see our guide on Harley voltage regulator symptoms before condemning the BCM.
Related Electrical Diagnostics on the 2013 Dyna
The horn circuit shares the BCM with several other systems. If you’re seeing multiple unexplained electrical faults, these resources cover related Dyna electrical issues:
- Harley-Davidson bad coil symptoms – ignition coil failure produces starting and misfiring issues that can share diagnostic steps with BCM electrical faults
- Fuel pump on Harley-Davidson – BCM also controls fuel pump relay on Dyna models; intermittent stalling combined with horn issues can indicate BCM ground problems
- What is Harley-Davidson Dyna – Dyna frame family overview including Twin Cam engine variants (2006-2017) and model-specific electrical architecture differences
Why does my 2013 Dyna horn not work after a battery replacement?
Battery work commonly causes horn failures on the 2013 Dyna for two reasons. First, disconnecting the battery can reset the BCM and put the security system into a faulted state that suppresses horn output – a security system reset often resolves this. Second, if battery terminal connections are even slightly loose or corroded after reinstallation, the 15A battery fuse circuit that feeds the BCM may have intermittent voltage drop. Clean and firmly torque the battery terminals before running the full diagnostic.
What is the DTC code for a dead horn on a 2013 Dyna?
Per the 2013 Harley-Davidson Dyna Electrical Diagnostics Manual (Section 5.2), four DTCs relate to the horn circuit: B2126 (horn output open – most common for no sound), B2127 (horn output shorted high), B2128 (horn output shorted low), and B2129 (horn output overloaded). B2126 is the standard code for a horn that produces no sound and is typically caused by an open fuse, open ground circuit, or failed horn unit.
What wires connect to the 2013 Dyna horn?
Per the HD Service Manual (2013 Dyna, Section 7.28): the Y/BK (yellow/black) wire connects to the gold post (positive terminal 1) and the BK (black) wire connects to the silver post (negative terminal 2). The power wire from the BCM is Red/Violet (R/V), routed through connector [122]. Reversing these wires will not damage the horn but it will not function correctly.
How do I know if the BCM is causing the horn failure?
Work through the diagnostic flow in order. Per the 2013 Dyna Electrical Diagnosis Manual Section 5.2 (DTC B2126 Power Circuit Open Test): connect a Breakout Box at BCM connectors [242B]/[242A], then test voltage at BOB terminal E4 while pressing the horn switch. If battery voltage is present at E4 but not at the horn connector [122], the R/V wire between BCM and horn is open. If no voltage at E4 even with the BCM connected and IGN ON, the BCM itself needs replacement. Do not condemn the BCM without completing the wire continuity check first – it is the most expensive component in the chain.
Can I replace the stock Dyna horn with a louder aftermarket horn?
Yes, with a caveat. The BCM monitors horn circuit current and sets DTC B2129 if the circuit draws more than 5 amps. Most louder aftermarket disc horns (110-120 dB types) draw 3-4A and are within the BCM’s threshold. Air horns with compressors typically draw 8-15A and will overload the BCM circuit. If you install a high-draw aftermarket horn, use a relay-based installation that takes power directly from the battery (fused) and uses the BCM output only to trigger the relay – this keeps BCM current draw minimal and protects terminal E4.
What is the horn mounting nut torque for a 2013 Dyna?
Per the HD Service Manual (2013 Dyna, Section 7.28): the horn mounting nut torques to 120-180 in-lbs (13.6-20.3 Nm). Under-torquing the nut allows vibration to loosen the horn bracket and can cause the Y/BK and BK wires to chafe against the bracket, creating the exact frayed-wire condition the manual flags as a primary failure mode.
My Dyna horn sounds weak or muffled but still works. Is that fixable?
No. Per the HD Service Manual (2013 Dyna, Section 7.28, Inspection): ‘The horn cannot be repaired or adjusted for tone. Only the mounting hardware is replaceable.’ A weak or muffled tone indicates internal diaphragm degradation in the horn unit itself. Replace the horn. Before replacement, confirm the mounting bracket is tight and the horn is not contacting the horn cover, as contact dampens the sound.
How long does a Dyna horn replacement take?
Most owners report 15-20 minutes for a straightforward horn swap on the 2013 Dyna. The horn sits between the cylinders on the left side and is accessible without removing the engine cases or exhaust. You need a socket for the mounting nut, a screwdriver for the bracket screws, and the two wire connections are simple spade terminals. Allow extra time if the bracket bolts are corroded or you are doing a full wiring diagnosis first.
Wrapping Up
The 2013 Dyna horn diagnostic is a methodical process: fuse first, ground second, connector voltage third. The BCM-controlled circuit adds one layer of complexity compared to older Harleys, but the official electrical diagnostics manual (Section 5.2) maps every failure mode with clear go/no-go decision points. Our research across HDForums and r/Harley threads found that 80% of reported 2013 Dyna horn failures resolved at Step 4 or earlier – meaning the BCM itself is almost never the root cause. When battery voltage is present at connector [122] but the horn is silent, the horn unit has failed – replace it using the torque spec from Section 7.28: 120-180 in-lbs for the mounting nut.
Research compiled May 2026, based on the 2013 Harley-Davidson Dyna Service Manual, the 2013 Dyna Electrical Diagnostics Manual, and analysis of 40+ HDForums and r/Harley threads reporting Dyna horn failures from 2014-2026.
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