WH-RTH Radio T Harness – Installation Manual

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Tools & Parts

Tools Required:

• Wire strippers
• Cutters
• Connectors or solder (if attaching to DSP)

Parts Provided:

 

• WH-RTH Radio T Harness (see figure 1)
  
• DSP modular power harness (see figure 2)
  
• Vehicle accessory power harness (see figure 3)
  
• RCA sub harnesses (see figures 5–8)
  
  
  
  
• Speaker input sub harnesses (see figure 9)
  
  

Preparation

• Skill Level: Beginner
• Estimated Time: 30 minutes

1. Park the motorcycle on a stable surface with handlebars centered.
2. ⚠ Warning: Disconnect the motorcycle battery before making wiring connections.
3. Remove the outer fairing if needed for access.

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Installation Steps

Main T Harness Connection

1. Disconnect the factory radio main wire harness.
2. Connect the WH-RTH T harness to the factory radio to connection point 1 (see figure 1).
3. Connect the WH-RTH T harness to the bike’s wire harness that was originally plugged into the radio to connection point 8 of the T harness.
   

   
   DSP Power Harness

4. If using a DSP, connect the DSP power harness (see figure 2) to connection point 5
   on the main T harness (see figure 1). a. Strip the unterminated yellow (12V) and black (ground) wires.
   b. Connect these to the DSP’s power input.
   c. Note: This circuit is live even with ignition OFF. Do not leave wires unterminated.
   
5. If not using a DSP, do not install the DSP power harness.
   

   
   Vehicle Accessory Power Harness

6. Connect the vehicle accessory power harness (see figure 3) to the factory accessory
   connector inside the fairing (see figure 4). The factory accessory connector can be found behind the voltage gauge. It is a black 2 pin male connector and usually has an empty female connector plugged into it.
   1. Remove the empty female plug from the unused 2‑pin accessory connector.
   2. Plug in the supplied accessory power harness.
      
      
7. Connect the harness as follows:
   1. With DSP: accessory harness → DSP trigger input → DSP trigger output →
      amplifier remote turn‑on.
   2. Without DSP: accessory harness → amplifier remote turn‑on.
   
   Note: The remote turn‑on circuit must be wired in this order to prevent turn‑on pop or timing issues. Beginners often connect all remote wires together at one point, which can cause loud pops or delayed startup. By routing the remote signal first through the DSP (when present) and then to the amplifier, the system powers up in the correct sequence and avoids these common
   issues.
   
   

   RCA Outputs

8. Connect front RCA sub harnesses (see figure 5):
   
   
   
   1. Left RCA (Black RCA with white & green wires) → connection point 4 (see figure1).
      
   2. Right RCA (Red RCA with red & black wires) → connection point 3 (see figure 1).
      
      
9. Connect rear RCA sub harness (see figure 6) to connection point 2 (see figure 1).
   
   
   

   RCA Modification for Non-Compatible Amplifiers

10. ⚠ Warning: Some amplifiers with common-ground RCAs can damage the factory radio. Most quality motorcycle amplifiers accept a high-level (speaker-level) signal through RCA connectors, but you must confirm this in your amplifier’s documentation. If your amplifier instead requires a dedicated high-level input via bare wires, you must modify this harness as described below. Check your owner’s manual for references to speaker-level RCA compatibility. If uncertain, test with a digital multimeter by measuring resistance between the outer rings (negative) of the RCA jacks. If the reading is less than several thousand ohms, the amplifier is not compatible with speaker-level RCA input.
11. If amplifier does not accept RCA high-level input:
    1. Cut RCA ends off the harness as shown (see figure 7).
       
       
    2. Wire color codes (see figure 8):
       
       
       1. Green = Left Negative
       2. Red = Right Positive
       3. Black = Right Negative
    
    Once cut, strip and terminate the colored wires as needed. Connect each positive and negative lead directly to the amplifier’s high‑level (speaker‑level) input terminals according to the color code above. Use quality crimp connectors or solder joints, and insulate with heat shrink to prevent shorts. Do not leave any unterminated wires exposed inside the fairing.
    

    
    Speaker Connections

     The speaker sub harnesses provide a clean way to intercept the factory speaker circuits without running new wires through the motorcycle. They plug into the WH-RTH harness at the designated points and present unterminated leads that connect directly to your aftermarket amplifier outputs. This allows you to use the bike’s existing speaker wiring while safely integrating your amplifier.

12. Connect front speaker sub harness to connection point 7 (see figure 1). Connect the
    following unterminated circuits to the aftermarket amplifier front outputs.
    
    
    1. White = Left Front Positive
    2. White/Black = Left Front Negative
    3. Gray = Right Front Positive
    4. Gray/Black = Right Front Negative
13. Connect rear speaker sub harness (see figure 9) to connection point 6 (see figure 1). Connect the following unterminated circuits to the aftermarket amplifier rear outputs
    
    
    

    
    Factory Amplifier Bypass
    

    Some Harley-Davidson touring models come from the factory with one or two amplifiers installed that must be bypassed. These factory amplifiers must be bypassed so the radio’s audio signals can be routed directly into your aftermarket system. Without a bypass harness, the stock amplifiers would block the audio path.
    
14. For bikes with factory amplifiers:
    
    1. Use American Hard Bag part WH-14-BYP-F for front amplifier bypass. This harness allows the radio’s front and rear audio signals to continue down the bike’s wiring without the factory fairing amplifier in place.
       
       
    2. For two‑amp bikes (one in the fairing and one in the saddlebag), also use American Hard Bag part WH-14-BYP-R for rear amplifier bypass as well as WH-14-BYP-F for front amplifier bypass. This ensures the rear speaker circuits are available for connection to your aftermarket amplifier. 
        
    3.  Bikes with three or four amplifiers: Some Harley-Davidson touring models are equipped with up to four factory amplifiers. In these setups, only the fairing amplifier and the left saddlebag amplifier need to be bypassed to integrate an aftermarket system. If the bike has tour‑pack speakers, new aftermarket speaker wiring must be added for them. The third and fourth factory amplifiers—those located in the right saddlebag and in the tour
       pack—use wiring schemes that are not compatible with aftermarket audio. For this reason, they should be removed from the system entirely rather than bypassed.
       
       Optional Slim Installation
       Note: This is an alternative configuration. Choose this method if space is both limited inside the fairing and if your installation does not require DSP battery power output. Slim installation simplifies wiring and reduces clutter but is not required if the full WH-RTH harness is already suitable.
       
       
15. For non-Ultra models without DSP power needs: a. Disconnect front speaker service
    connectors at each of the fairing speaker enclosures. b. Plug front RCA sub harnesses directly into bike harness that you just unplugged from the enclosure. c. Use American Hard Bag part WH-SP-POD or American Hard Bag part WH-FPOD harnesses to connect aftermarket amplifier outputs back to front speakers.
    
    
16. For rear RCA on non-Ultra models:
    1. Locate the unused 4‑pin black Molex MX150 rear speaker output connector, which branches off near the radio harness on the clutch side of the fairing. This is the factory rear speaker output connection point that the dealer uses when they add rear speakers to a bike that shipped from the factory with only front speakers. This connector may have a rubber plug installed for weather sealing; remove it to access the rear RCA connection point.
    2.  Remove plug, connect rear RCA harness.
       
    3. On CVO models, connector is under the seat and is not located behind the radio.
17. For Ultra models: always use full WH-RTH harness for rear RCA and speaker access.
    The slim installation is not an option for Ultra models.
    
    Some Harley-Davidson touring models come from the factory with one or two amplifiers installed that must be bypassed. These factory amplifiers must be bypassed so the radio’s audio signals can be routed directly into your aftermarket system. Without a bypass harness, the stock amplifiers would block the audio path.
    
18. For bikes with factory amplifiers:
    1. Use American Hard Bag part WH-14-BYP-F for front amplifier bypass. This harness allows the radio’s front and rear audio signals to continue down the bike’s wiring without the factory fairing amplifier in place.
    2. For two‑amp bikes (one in the fairing and one in the saddlebag), also use American Hard Bag part WH-14-BYP-R for rear amplifier bypass as well as WH-14-BYP-F for front amplifier bypass. This ensures the rear speaker circuits are available for connection to your aftermarket amplifier.
    3. Bikes with three or four amplifiers: Some Harley-Davidson touring models are equipped with up to four factory amplifiers. In these setups, only the fairing amplifier and the left  saddlebag amplifier need to be bypassed to integrate an aftermarket system. If the bike has tour‑pack speakers, new aftermarket speaker wiring must be added for them. The third and fourth factory amplifiers—those located in the right saddlebag and in the tour pack—use wiring schemes that are not compatible with aftermarket audio. For this
       reason, they should be removed from the system entirely rather than bypassed.

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Verification & Testing

1. Reconnect motorcycle battery
2. Turn ignition to Accessory.
3.  Verify:
   
   1. Amplifier(s) or DSP power on correctly.
   2. Audio present at all speakers.
   3. Remote turn‑on functions as expected.

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Troubleshooting

Symptom	Likely Cause	Fix
No power to DSP	DSP harness not connected to point 5	Verify harness connection
No amplifier turn-on	Accessory power harness miswired	Check accessory harness routing
No sound from speakers	RCA harness not seated	Reseat RCA connectors
No audio	Amplifier not compatible with RCA high-level	Modify harness to direct wire-level connections (cut RCA ends and connect bare wires)