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Motorcycle H4 Headlight Relay Kits

Installation instructions are here

Finally! An easy way to get a lot more light from your headlight. Adding relays will make any bulb put out it’s full intensity. Your headlight bulb’s Voltage drop after installing this kit will be a mere .1 Volt! (that’s point one Volt) You will be amazed at your stock bulb’s output! Even on a brand new bike you will notice an incredible difference in the headlight output.

Easy Plug-In Install: Most H4 Kits just plug into your bike’s existing wiring. No cutting of your bike’s wiring is needed. You plug into your headlight bulb socket and headlight bulb, connect to the bike battery and you’re all set!

Perfect Set of Components: Two high quality relays are provided - one for low beam, one for high beam. Included is a weather proof inline fuse holder, two fuses, and enough cable ties to strap the wiring to your bike. All wiring is high temp cross linked type.

Relay kits work fine with modulators! - just make sure the modulator goes directly on the bulb(s) and the Kit’s H4 sockets go onto the modulator(s).

About the Coupler Connection - PLEASE READ

Most H4 Kits now have an option for either an H4 Coupler to plug into your stock bulb socket for HI and LO beam switching. As an alternative you can remove the H4 Coupler and make a more secure and tidy connection using a pair of Posi-Locks or you can solder these wires. There are some pros and cons for each as I will note here:

Option 1 - H4 Coupler:

PROS: Easier install, just plugs into your old H4 Socket. Easy to remove later if you sell the bike. Easy to reconnect the old H4 socket to the bulb if you have a problem with the Kit. I would consider a Relay Kit a permanent install on that bike so NOT using the Coupler makes sense to me.

CONS: Coupler/Socket combo makes a bulky unit you have to wrap and tie up somewhere safely. It’s more difficult to fit inside a crowded headlight shell. Old headlight H4 socket must be taped up to avoid shorting exposed terminals.

h4coupler-socket


Option 2 - Posilock Connection:

PROS: Removes the bulky coupler/socket unit. Avoids poor connections with an old corroded plug. Makes installing inside a headlight shell easier with less bulk. Avoids any potential shorting of old H4 socket terminals.

CONS: Requires cutting off bike’s old H4 Socket. Not as easy to remove Kit later if you sell the bike.  Posi-Locks join the hot wires from your old headlight to the Kit’s 2 coupling wires. These connections switch the new relays using your HI/LO switch.

Posilock Option with Relay Kits

You get - 2 Posilocks PL1416 and 2 pieces of dual wall 3/8” shrinktube

h4connection-posi

Install the Posilocks, cover with shrinktube, heat, and you have neat sealed connections.

h4connection-posi-2


Option 3 - Solder/Shrinkwrap Connection:

Requires crimper or soldering skills. You can connect these wires in many different ways. For example you could use a set of connector housings, either sealed or unsealed.

 If you use insulated butt connectors, please do not think that pinching them with pliers is good enough. These connections don’t pass high current but are important for headlight operation.


My Recommendation: I believe that a Relay Kit should be a permanent part of your bike. I like neat and tidy installs and I don’t like old plugs, bulky connectors that are unecessary, or possible bad connections. Installing sealed Posi-Lock connectors instead of the H4 Coupler really cleans up the area around the back of the headlight or inside the shell.

Click a Quick Link below to jump to the Kits and Options on this Page:

H4 Single  -  H4 Dual  - Positive Ground  -  Weatherproof Single - Weatherproof Dual

H4 Single Headlight Relay Kits

H4 Single ‘In Shell’ Kit

 

h4s-s-900

This Kit is has short bulb leads for fitting the relays inside a headlight shell.

Specifications:

Main leads 61” (155 cm) AWG 14 (2 sqmm) high temp cross linked Yazaki wire covered with high temp sheathing

Bulb leads 6” (15 cm) - for installing the relays inside a headlight shell

Two heavy duty 20A Panasonic Relays socketed into the wiring

Cooper-Bussman ATM Fuseholder with two 15A fuses is removable with a bullet connector to make running wires easy

Includes cable ties to secure your Kit to your bike

Fusepanel Connection option - main lead wires are longer and sheathed to 6 in (15 cm) from ends.

Choice of H4 Coupler or a Sealed Posilock option for relay triggering - see H4 Coupler Connection above.

3 Circuit Solution option has a main lead connector to plug into my 3CS-HD.

 

 

H4 Single ‘In Shell’ Relay Kit $64.95

Coupler Option
Main Leads Connection

LO Cut Integrated into this Kit (must buy both at same time) $9.95

Switch Connectors

   


H4 Single ‘In Fairing’ Kit

 

h4s-f-900

 

This Kit is has longer bulb leads for fitting the relays remotely in a fairing, where there is no regular headlight shell.

Specifications:

Main leads 61” (155 cm)

Bulb leads 16” (40 cm) - allows the relays to be remotely mounted from the headlight

Two heavy duty 20A Panasonic Relays socketed into the wiring

H4 Coupler makes installation easy by plugging into your stock headlight socket for relay triggering

Cooper-Bussman ATM Fuseholder with two 15A fuses is removable with a bullet connector to make running wires easy

Includes cable ties to secure your Kit to your bike

Fusepanel Connection option - main lead wires are longer and sheathed to 6 in (15 cm) from ends.

Choice of H4 Coupler or a Sealed Posilock option for relay triggering - see H4 Coupler Connection above.

3 Circuit Solution option has a main lead connector to plug into my 3CS-HD.

 

 

H4 Single ‘In Fairing’ Relay Kit $66.95

Coupler Option
Main Leads Connection

LO Cut Integrated into this Kit (must buy both at same time) $9.95

Switch Connectors

   


H4 Single with Driving Lights Lead

 

h4-p_1802

This Kit is an H4 Single ‘In Shell’ Headlight Relay Kit with an extra lead for powering ‘Driving Lights’ as found on Harleys and other cruisers. Relays go inside the headlight shell. The extra lead plugs into the toggle switch to power the driving lights.

Fusepanel Connection option - main lead wires are longer and sheathed to 6 in (15 cm) from ends.

Choice of H4 Coupler or a Sealed Posilock option for relay triggering - see H4 Coupler Connection above.

3 Circuit Solution option has a main lead connector to plug into my 3CS-HD.

 

 

H4 Single Relay Kit with Driving Lights on with LO Beam $68.95

Coupler Option
Main Leads Connection

H4 Single Relay Kit with Driving Lights on with HI Beam $68.95

Coupler Option
Main Leads Connection

LO Cut Integrated into this Kit (must buy both at same time) $9.95

Switch Connectors

   


H4 Single Headlight Weatherproof Relay Kit

h4w_2029

This Kit is specially for bikes like the BMW R1100GS which has a tight fitting headlight housing cover. Also, this Kit is for bikes with a very small headlight shell. This Kit allows easy insertion of the bulb leads into the headlight shell. The Kit is shipped with bulb leads out of the socket and they are then plugged in after installing the wires into the headlight housing. The relays can be mounted further back, either in the fairing or under the front of the fuel tank. The relays are shrink wrapped to keep out dirt and moisture.

Specifications:

Main leads 57” (145 cm)

Bulb leads 20” (50 cm)

Posi-Locks included with shrinktube for HI/LO connection instead of H4 Coupler

Fusepanel Connection option - main lead wires are longer and sheathed to 6 in (15 cm) from ends.

3 Circuit Solution option has a main lead connector to plug into my 3CS-HD.

 

 

H4 Single Weatherproof Relay Kit $69.95

Main Leads Connection

LO Cut Integrated into this Kit (must buy both at same time) $9.95

Switch Connectors

   


H4 Single Positive Ground Headlight Relay Kit

H4 Single Positive Ground Headlight Relay Kit

This Kit is specially for older British and other makes which have a positive ground electrical system. This Kit is basically the same as the regular H4 Single ‘In Shell’ Kit, except the wire colours are reversed with red wiring for the ground circuits. It is designed to connect directly to the battery.

 

 

H4 Single Positive Ground Relay Kit $64.95


LO Cut Integrated into this Kit (must buy both at same time) $9.95

Switch Connectors

   


H4 Dual Headlight Relay Kit

 

H4 Dual

This Kit is for bikes with dual fairing mounted H4 headlights. See here for bikes with dual headlight shells.

Fusepanel Connection option - main lead wires are longer and sheathed to 6 in (15 cm) from ends.

Choice of H4 Coupler or a Sealed Posilock option for relay triggering - see H4 Coupler Connection above.

3 Circuit Solution HD option has a main lead connector to plug into my 3CS-HD.

 

H4 Dual Relay Kit $77.95

Coupler Option
Main Leads Connection

   

 Triumph Rocket III Owners - I now have a special H4 Dual Kit for your bike, look here. Note, some Rocket III bikes have an H4 Single headlight and can use my H4 Single In Shell Headlight Kit at the top of this page.

 Bikes with Twin Headlight shells with H4 bulbs can use the Rocket III Kit.


H4 Dual Headlight Relay Kit with LO Beam On/Off Switching

h4d-lobeam-switch_0311

This Kit is specially for those who want the ability to cut their headlight at startup, or for any other reason (low battery etc).

This Kit will switch the LO beam of BOTH headlights using a SPST switch.

See my Switches Page for a switch for this Kit.

Choose a Kit with switching connectors according to the switch you will use. If you want to mate with the Handlebar Switch, choose the Bullet Connectors Kit. 1/4 inch pushons will connect to many switches that have 1/4” tabs.

Switching takes place on the low current LO beam relay trigger wire, not on the headlight bulb wires, thereby giving you full power to both headlights when ON, without any Voltage drop inherent in in-line bulb lead switching.

Fusepanel Connection option - main lead wires are longer and sheathed to 6 in (15 cm) from ends.

Choice of H4 Coupler or a Sealed Posilock option for relay triggering - see H4 Coupler Connection above.

3 Circuit Solution option has a main lead connector to plug into my 3CS-HD.

 

H4 Dual Relay Kit with LO Beam ON/OFF Switching (1/4” pushons) $87.95 

Coupler Option
Main Leads Connection

H4 Dual Relay Kit with LO Beam ON/OFF Switching (bullet connectors) $87.95 

Coupler Option
Main Leads Connection

   

Note, bullet connection has shorter switching wires because of wiring on the barswitch, to avoid excessive wire length. This Kit assumes you will use my Handlebar Switch or equivalent with 4mm bullets.


H4 Dual Headlight Relay Kit with One Headlight Cut Adapter Built in

Same H4 Dual Kit but with built in wiring for a Headlight Cut Switch (DPST). H4 Headlight cut adapters only are available separately here.

This Kit cuts both beams of one H4 Socket, in fact the one with the shorter leads. If you want to cut the right headlight, bring in the Kit’s main wiring from the right side. To cut the left headlight, bring in the main wiring from the left side.

You can buy a DPST switch for this Kit here (Toggle) or here (Rocker).

PLEASE NOTE - YOU CAN’T USE THE SPST ON/OFF BARSWITCH WITH THIS KIT.

Fusepanel Connection option - main lead wires are longer and sheathed to 6 in (15 cm) from ends.

Choice of H4 Coupler or a Sealed Posilock option for relay triggering - see H4 Coupler Connection above.

3 Circuit Solution option has a main lead connector to plug into my 3CS-HD.

 

h4dual-with-hl-cut_1111
The kit above has the H4 Coupler option and Fuse Panel main leads (bare wires)

 

H4 Dual Relay Kit w/ One Headlight Cut Wiring $91.95

Coupler Option
Main Leads Connection

   


H4 Dual Headlight Weatherproof Relay Kit - Install Page Here.

This Kit is made specially for those bikes like the Triumph Rocket III, which have two separate headlight shells. Also great for custom bikes with twin billet headlight shells.

 

h4d-w

Features:

- both bulb leads longer (puts relays under front of gas tank)

- H4 Sockets left off for easier shell insertion

- relays shrink wrapped (keeps moisture out of wiring)

- relays slightly farther apart (easier to mount relays)

- Posi-Locks instead of H4 Coupler (no bulky Socket/Coupler)

Fusepanel Connection option - main lead wires are longer and sheathed to 6 in (15 cm) from ends.

The 3CS Connection option has a main lead connector to plug into my 3 Circuit Solution HD.

NOTE: This Kit is also great for other bikes with two separate H4 headlight shells: Street Triple, etc.

 

H4 Dual Weatherproof Relay Kit $88.95

Coupler Option
Main Leads Connection


H4 Lo or Hi Beam Cut Adapters  -  Cuts one beam on one headlight.

Specially for the VStrom but will work on any H4 System, this adaptor allows you to turn off and on one headlight using any switch taking push on blade terminals. It’s available with push on spades, bullet connectors or Posi-Locks.

This Kit will work with one of my H4 Headlight Relay Kits or with a stock H4 system.

Works on HI or LO beam (depending on model), saves 55 (60 for HI beam) watts of power for your other accessories.

Now you can run a pair of Auxiliary Lights and get that triangulation that you need to be noticed by cars.

All high temperature 100o wire, with high temperature AH-6 sheathing.

Sumitube shrinktube on all terminal crimps to seal out moisture and give excellent strain relief.

H4 Socket plugs onto your one headlight bulb.

Your existing headlight socket plugs onto he H4 Coupler.

36” (92 cm) of wire is enough to reach to the fairing inner panel or to a handlebar switch.

Choice of switch connectors, push on female spades (.250” or .187”), bullet connectors, or Posi-Locks.

Order a switch to go with the adaptor here. I recommend a switch of at least 10A capacity.

 

headlight-cut-adaptor

H4 Lo Beam Cut Adapter $39.95

Switch Connectors
Quantity:

HI-beam-cut-adaptor

H4 Hi Beam Cut Adapter $39.95

Connectors
Quantity:


H4 Lo or Hi Beam Cut Adapter with Handlebar Switch

H4 Lo or Hi Beam cut adapter with bullet connectors, in combination with a handlebar switch.

Complete unit, just plug the headlight end between one bulb and its socket, attach the switch to your bars, run and cable tie the wires and you’re all set. Includes cable ties.

Handlebar switch is available separately on the Switches Page.

NOTE: A customer has informed me that on his VStrom 650, this switch won’t fit on the left side due to the bent clutch lever. However it will fit on the right side of the bars.

 

headlightcut_barswitch

 

HI-beam-cut-adaptor-with-sw

 

H4 Lo or Hi Beam Cut Adapter with Barswitch $54.95

Beam Cut
Quantity:

 

Handlebar switch mounted on DL1000. The mirror had to be moved about 3/16”.

barswitch-on-strom


H4 Headlight Cut Adapter -  Cuts both beams on one headlight.

Works on any H4 System, this adaptor basically disables or enables one of your headlight bulbs at the flick of a switch.

Works on both beams of one bulb, saves 55-60 watts of power for your other accessories.

Now you can run a pair of Auxiliary Lights and get that triangulation that you need to be noticed by cars.

All high temperature wire, with high temperature sheathing.

Sumitube shrinktube on all terminal crimps to seal out moisture and give excellent strain relief.

H4 Socket plugs onto one of your headlight bulbs. Can be used with or without my H4 Dual Relay Kit.

The removed headlight socket then plugs onto the H4 Coupler.

36” (92 cm) of wire is enough to reach to the fairing inner panel or to a handlebar switch.

You will need a DPST switch for this adaptor. See here (toggle) or here (rocker) for a switch for this adaptor.

Or you can use it with two SPST switches to control each headlight’s beam separately.

 

headlight-cut-adaptor2

 

H4 Headlight Cut Adaptor $48.95

Quantity:

 

Why not pick up a few extra Posi-Locks and Posi-Taps with your Kit? Great for all wiring, even around the house!