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Manual Installation

WH-PNP-R Rear Audio Signal Adapter – Installation Manual

Vehicle Compatibility: 2014–2023 Harley-Davidson Street Glide, Road Glide, Electra Glide.
Not compatible: Ultra models. Some CVO models route rear output under the seat (see Notes below).

Tools & Parts

  • Digital multimeter (DMM) — verify RCA ring-to-ring resistance and signal presence.
  • RCA cables — reach the aftermarket amplifier inputs. Some CVO require ~6 ft RCA
    extension from under-seat to fairing.
  • Zip ties — secure the harness to factory loom.
  • Wire cutters/strippers + butt connectors/solder & heat-shrink — only if performing
    the modification procedure for non‑RCA high‑level amplifiers.
  • TechnoResearch® flash tool (dealer/installer access) — apply the American Hard Bag
    profile.


Included: WH-PNP-R harness with load resistors and RCA connectors.
Related (not included): WH-PNP-F (front signal version; different connection point/style).

Installation Steps

  1. Locate the factory rear speaker output connector. Find the black 4‑pin male connector with a rubber plug on the fairing harness behind the radio.

    An image of the WH-PNP-R wire harness with callouts for the 4 pin connection to the radio, the load resistors, and the RCA connectors.

    Figure 2

    an image of a Harley Street Glide with the fairing removed showing the 6 most important connection points on the bike for audio systems including the factory radio rear speaker connection point that the WH-PNP-R connects to for signal.


    Figure 5

  2. Remove the rubber plug. Pull the plug straight out of the 4‑pin connector.
  3. Connect the WH-PNP-R to the 4‑pin radio connector. Push until fully seated; verify latch engagement.
  4. Route the RCA leads to the amplifier location. Follow the factory loom and avoid pinch points/sharp edges. Secure with zip ties.
  5. Connect the RCA outputs to the aftermarket amplifier inputs. Insert left/right RCA plugs into the amplifier’s input.
    ⚠ Warning: The WH-PNP-R is not a high‑to‑low converter; signal at the RCA ends is speaker level (>8 V balanced). Your amplifier must accept speaker‑level over RCA.
  6. Special case – some CVO models. If the bike’s rear output is not available in the fairing it can be found under the seat, extend the signal to the fairing using an approx. 6 ft RCA cable, then proceed with Step 7.
  7. Perform the radio flash (TechnoResearch). Use the TechnoResearch tool to select the American Hard Bag profile and apply the flash. See Radio Flash Behavior below.
  8. Finalize harness management. Dress and secure wiring; verify no interference with fairing reinstallation.
An image of the WH-PNP-R wire harness with callouts for the 4 pin connection to the radio, the load resistors, and the RCA connectors.


Figure 2

an image of a Harley Street Glide with the fairing removed showing the 6 most important connection points on the bike for audio systems including the factory radio rear speaker connection point that the WH-PNP-R connects to for signal.

Figure 5

Harness Modification Procedure — For amplifiers without high-level input over RCA

Use only if your amplifier requires a dedicated high‑level plug (not RCA) and does not support speaker‑level over RCA.

  1. Verify amplifier input type. Measure resistance between the outside rings of the
    amplifier’s RCA inputs with a DMM. A reading in the thousands of ohms indicates
    typically compatible; zero/near-zero ohms indicates not compatible over RCA (use thisprocedure).
  2. Cut the WH-PNP-R as shown. Cut at the marks in 
    An image of the WH-PNP-R wire harness with a wire cutter tool icon and dashed lines showing where the harness should be cut for modification.
    Figure 3
    to remove the load
    resistor section and the RCA connectors.
  3. Prepare the amplifier’s high-level pigtail. Locate the amplifier’s supplied high‑level
    input harness (pigtail with unterminated leads).
  4. Match and splice wires per color legend. Use 
    this image shows the cut wire harness as well as a wire color legend the user can use to identify the channel and polarity of each wire to be spliced into the amplifier’s high level input pigtail.

    Figure 4
    to identify channel and
    polarity. Splice each WH-PNP-R wire to the corresponding pigtail lead.
    Note: Depending on pigtail length, you may need to extend leads to reach the amplifier.Use solder & heat‑shrink or quality crimp connectors.
  5. Secure and protect splices. Insulate each joint and add loom as needed.
An image of the WH-PNP-R wire harness with a wire cutter tool icon and dashed lines showing where the harness should be cut for modification.Figure 3
this image shows the cut wire harness as well as a wire color legend the user can use to identify the channel and polarity of each wire to be spliced into the amplifier’s high level input pigtail.


Figure 4

Important Compatibility Note (Reference)

This adapter is not a high‑to‑low level converter. The RCA connections carry full speaker‑level audio. Most quality motorcycle‑specific amplifiers accept high‑level over RCA. Some products require a dedicated high‑level plug instead. Consult your amplifier’s manual. If needed, use the Harness Modification Procedure above.

Quick check: DMM resistance ring‑to‑ring on the amplifier’s RCA inputs should read in the kΩ range for compatibility. 0 Ω / near‑0 Ω = incompatible via RCA.

Radio Flash Behavior (TechnoResearch — American Hard Bag profile)

Flashing the radio means reprogramming its software settings with a specialized tool. Harley radios are shipped with profiles tailored to factory equipment, and many useful audio features are disabled. A TechnoResearch brand flash tool updates the radio to recognize aftermarket gear, turning on hidden functions and optimizing the output signal. Without a flash, the WH-PNP-R may not deliver any rear audio signal.

  • Rear output & Fader: Enables rear audio out and front–rear fader (disabled from the
    factory). If fader shows but was non‑functional, the flash restores that operation.
  • Tone controls: Ensures Bass and Treble operate even without a factory amplifier.
    Some factory configurations process tone/fader/EQ inside the factory amplifier; removing it breaks these controls until flashed.
  • EQ curve: Applies an EQ that is friendly to aftermarket equipment.
  • Signal level: Reduces radio output level but keeps it speaker‑level (>8 V balanced),
    suitable for most DSPs/amplifiers with balanced-over-RCA inputs.
  • Dynamic EQ retained: Keeps the Harley dynamic equalization (loudness-style curve)
    that varies with volume, improving clarity at varying road noise and volume settings.

Verification & Testing

  1. Power up the system. Turn ignition ON and power the amplifier.
  2. Check fader operation. On the Boom!™ radio display, verify Fader control is present
    and adjusts front vs. rear.
  3. Verify channel mapping. Play test audio; confirm left/right and front/rear are
    positioned correctly.
  4. Confirm tone controls. Adjust Bass and Treble.
  5. Listen for distortion at moderate volume. If distortion occurs early, re‑check amplifier input mode/settings.
  6. Inspect harness routing and clearance. Cycle bars lock‑to‑lock; check panel fit.

Note: If using the modification procedure, repeat Steps 2–5 focusing on correct channel polarity and absence of engine noise.

Troubleshooting

Symptom
Likely Cause 
Fix
No rear sound  Radio not flashed / Fader disabled Apply TechnoResearch flash with American Hard Bag profile; re‑test.
Fader shows but has no effect Flash not applied correctly / wrong profile Re‑flash; verify profile selection.
Distortion at low volume Amplifier incompatible
with speaker‑level over
RCA		 Switch amplifier to high‑level‑over‑RCA mode (if available) or perform Harness Modification Procedure.
No sound after RCA connection RCA leads connected to
wrong input / mute or
DSP bypass		 Verify amplifier input selection and gain; check DSP routing.

v1.0, 2025-09-18

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