Headlight rewiring with relays

Jeffrey L. Walker walkerjl at charter.net
Thu Mar 13 22:04:03 PDT 2008

A)  I have rewired both my high beam and low beam.  I ran heavy gauge (8 or
10 gauge) wire directly off the battery.  I used two separate SPDT relays,
high beam and low beam.  I used the stock headlight wiring to energize /
activate the relay coils.  This part of the circuit (stock headlight wires)
now carries only minimal current, just enough to activate the coil, probably
only a couple milivolts. 

The main current to the headlight now comes through the heavy gauge wire,
with very little voltage drop.  I noticed an immediate improvement with the
stock headlight.  But of course I soon installed an (illegal) 80W - 100W
headlight bulb.

Couple of points:  With any relay that I've installed on the bike (one for
the horn too), I potted them (waterproofed) as best I could with a sealant
epoxy.  Even so, I had one relay (low beam) burn out because it was corroded
after water entered it.  The key is to mount them right side up, with the
terminals pointing down.  After I remounted it right side up, I've never had
that problem again.  

I mounted the relays inside the upper fairing, attached on each side of the
headlight housing. I wired in with a homemade wiring harness.  I had to use
spade terminals (male and female) as quick connects on this wire so I can
remove the upper fairing for maintenance easily.  This really is the weakest
part of my setup, as I have to re-wrap it with electrical tape every time.

Don't forget that you need to also improve the ground wire.  You don't have
to go to the negative battery terminal, but you do have to have a very good
ground point, and use the same gauge wire as you did with the positive wire.

My setup is slightly more complex than this, as I also have a Kriss
headlight modulator wired in there too, which is also wired up and attached
inside the upper fairing by the headlight housing. (On top if I'm
remembering right.)

B)  Stock wiring:  The design logic is that the headlight is only activated
after the motor is started.  I turn the key on, the front running lights,
instrument lights, and tail lights turn on, but not the headlight.  I assume
the reason for this is to minimize the drain on the battery to ensure
adequate starting voltage.  After the motor starts, the control relay
latches and seals it in (the headlight stays on after killing the motor with
the run/stop switch.)  It actually makes perfect sense, in that the intent
is to minimize unnecessary battery drain.  Anyway, just tap into its output
for energizing the relays.

Good luck,
Jeff in Washington

Message: 9
Date: Wed, 12 Mar 2008 23:53:31 -0500
From: "William K Denton" <wkdenton at verizon.net>
Subject: headlight rewiring with relay
To: "GPz List" <gpzlist at micapeak.com>
Message-ID: <004b01c884c6$3acd8e40$6505a8c0 at D72H4BB1>
Content-Type: text/plain; format=flowed; charset=iso-8859-1;

Hi all,

I'm thinking about rewiring the headlamp circuit on the '96 GPz1100 with 
heavy gauge wire and a SPDT relay to improve lighting performance and leave 
the door open for increasing the wattage w/o worrying about melting wires. 
Just wondering:

A) anyone has already done this?... and

B) can anyone shed light on the circuitous path that the electricity makes 
through the OEM headlamp circuit in the shop manual?  I'm not sure I fully 
understand the reason behind all the components in the circuit (i.e. the 
headlight relay in the junction box "plus" the separate headlight relay 
unit; both shown on pp15-43 in the shop manual schematic, lower drawing).  I

also think there may be a misprint in the schematic, as there's nothing in 
the junction box connecting to the BR/W wire coming out of it.

Bill in Yardley, PA
wkdenton at verizon.net
'96 GPz1100

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