American Hard Bag WH-BYP-RF – Installation Manual

Tools & Parts

• Tools Required
  • Wire cutters/strippers
• Parts Required
  • WH-BYP-RF — Amplifier Bypass Harness (American Hard Bag)
  • WH-RTH — Radio T Harness (American Hard Bag)
  • WH-FPOD or WH-14-PNP-P — Front Speaker Wire Harness (American Hard
    Bag)

Introduction

Purpose and Application

The WH-BYP-RF is an amplifier bypass harness designed for Harley-Davidson touring
motorcycles equipped with a factory-installed Rockford Fosgate amplifier. Its purpose is to
remove the factory amplifier from the signal path without requiring modification to the
saddlebags or factory wiring. When used together with the WH-RTH Radio T Harness and either the WH-FPOD or WH-14-PNP-P Front Speaker Wire Harness, the bypass kit provides a clean signal path for aftermarket amplification and allows you to install a much more powerful 4-channel aftermarket amplifier in the fairing and delete the factory amplifier from the saddlebag. This ensures proper integration, preserves factory connectors, and simplifies upgrades.

Factory Rockford Wiring

2021–2023 Harley-Davidson touring bikes that come factory equipped with a single 4‑channel Rockford Fosgate amplifier in the left saddlebag are wired differently from Harley’s Boom! Audio systems. In these Rockford systems, the radio only sends two channels of front audio to the amplifier. The amplifier then internally splits those two channels into four (two front and two rear) and manages front-to-rear fading by digital communication over the factory data bus. This design works fine with the factory amplifier, but it does not translate when using aftermarket amplifiers, which have no way of communicating over the Harley data bus.

How the Bypass Harness Works

The WH-BYP-RF harness solves this by rerouting signals. When installed along with the
WH-RTH Radio T Harness and a front speaker harness (WH-FPOD or WH-14-PNP-P), the system reassigns the radio’s rear audio outputs at the T harness to serve the new fairing mounted aftermarket amplifier which then drives the rear lid speakers. At the saddlebag, the WH-BYP-RF bypass harness then directs that signal straight to the lid speaker connectors, completely avoiding the factory amplifier. Meanwhile, a new front speaker wire harness is used to connect the fairing speakers directly to the aftermarket amplifier in the fairing. This arrangement provides true four-channel output from the radio to the aftermarket amplifier and restores normal fader and tone control behavior once the radio is flashed.

Preparation

1. Verify motorcycle compatibility: 2021–2023 Harley-Davidson touring models with GTS radios and a single 4-channel Rockford Fosgate factory amplifier in the left
   saddlebag. The amplifier will have Rockford Fosgate branding on it. This kit will not work with non-Rockford factory supplied amplifiers.
2. Disconnect the negative battery cable to prevent electrical shorts.
3. Place motorcycle on a stable lift or stand for safe access to saddlebags and fairing.
4. Allow 30–45 minutes for installation depending on skill level.

Note: This procedure requires reassigning speaker channels. Review the wiring diagram before starting. [Figure 2]: Diagram of all wire harnesses with detailed descriptions

Installation Steps

1. Remove the left saddlebag mounted factory Rockford amplifier. This exposes the
   amplifier connections that will be bypassed.
2. Install the WH-BYP-RF Amplifier Bypass Harness by plugging it into the amplifier wire harness where the factory amplifier used to be plugged into. This harness bridges the factory rear speaker lines on the bike to the lid speakers, preserving use of the stock connectors on the bag.
3. Install the WH-RTH Radio T Harness at the GTS radio.
   1. Use only the front speaker inputs from the T harness. These outputs are reassigned to feed the rear lid speakers. Connect them to the amplifier's rear channels
   2. Leave the rear speaker outputs from the T harness (Green, Green/Black, Violet, Violet/Black) unused because they are not valid in Rockford-equipped systems.
4. Connect the front speaker inputs from the radio T harness to the aftermarket amplifier rear channels:
   1. White (+) / White-Black (–): Connect to Channel 3 (Left Rear).
   2. Gray (+) / Gray-Black (–): Connect to Channel 4 (Right Rear).
5. Connect RCA outputs from the radio T harness to the aftermarket amplifier for all 4 channels.
6. Choose either the WH-14-PNP-P or the WH-FPOD harness (do not use both).
   1. (WH-14-PNP-P) Use the supplied 2-pin female to unterminated red/black
      wires to connect the aftermarket amplifier (channels 1 & 2) directly to the factory fairing speaker pod connectors. This bypasses the factory fairing speaker circuits and delivers full power from the new amplifier.
   2. (WH-FPOD) Plug the two female 2‑pin connectors into the fairing speaker pods. Connect the wires to the amplifier front outputs (channels 1 & 2) as follows:
      1. White = Left Front Positive
      2. Green = Left Front Negative
      3. Red = Right Front Positive
      4. Black = Right Front Negative
7. Disconnect and do not reuse the factory fairing speaker wiring, as it no longer carries a signal.
8. Verify all harnesses are secure, routed away from moving parts, and free of pinch points.

⚠ Warning: Do not attempt to use the bypass kit without the required WH-RTH and
WH-FPOD/WH-14-PNP-P harnesses. Without them, audio channels will not be correctly routed, and the system will not function as intended.

Verification & Testing

1. Reconnect the negative battery cable.
2. Power on the motorcycle and GTS radio.
3. Verify operation:
   1. All speakers play
   2. Confirm fader and tone controls function correctly after flashing.

Note: GTS radios must be flashed with a TechnoResearch flash tool using the American
Hard Bag flash profile. Without flashing, sound will be present but equalization will be incorrect and volume scaling inconsistent.

Troubleshooting

Symptom	Likely Cause	Fix	Explanation
No sound from lid speakers	Wrong T harness outputs used	Recheck wiring; use front Inputs only	In Rockford systems, only the radio’s front channels are valid. If you connect the rear outputs at the T harness, no signal will reach the bypass harness or lid speakers.
Sound but poor EQ	Radio not flashed	Perform TechnoResearch flash with AHB profile	Without the flash, the radio still outputs audio but with factory EQ curves designed for the Rockford amplifier. These curves sound very bass and treble heavy or distorted when used with aftermarket amplifiers.
Fairing speakers silent	Factory wiring still connected	Disconnect factory fairing wiring; connect via supplied leads	The factory harness to the fairing pods is cut off once the bypass is installed. If still connected, those wires carry no signal. The aftermarket amplifier must connect directly via the supplied leads.

v1.0, 2025-09-10