Author Topic: Fan Circuit Modification. ( ST1100 ) *  (Read 5673 times)

Offline KoTAOW

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Fan Circuit Modification. ( ST1100 ) *
« on: May 21, 2009, 07:16:31 AM »
Original article can be viewed here:

written by Charlie Woods, STOC 002.

Fan Circuit Modification

Here in Texas and in traffic, the fan on my 1996 Standard cycles on and off....

Occasionally, the fan is still running when I'm ready to turn the bike off and pull the key....

If you re like me and sometimes kill the engine and turn the key back on to let the fan run until it stops..... READ ON

Most of the cars today with electric fans behind the radiator will run after the fan after the engine
and key are off. I suppose this is to prevent the now uncirculated water from reaching the boiling point.

Why doesn t the ST (or for that matter) all water cooled bikes with electric fans do the same?
Some checking indicates that the fan on the ST draws about 6 amps. So, you d have to run the fan for
2 hours without the charging circuit working to actually run down the battery....

I decided to FIX this.... The fan will now run after the key is turned off....

    12 volts positive is routed through the key. The
    ground for the fan is provided by the thermostat.
    So, it was simple to find unswitched 12 volts positive
    to connect the fan to.

The procedure is easier than removing the necessary Tupperware to get to the wiring harness:

Step 1)  Remove the seat
Step 2)  Remove the left side cover (the one that covers
             the battery (kick stand side).
Step 3)  Remove the tank shelter
Step 4)  Locate the large bundle of wires just below and
            aft of the air box... hint - its the big one
            on the side of the bike....
Step 5)  Remove 4 or 5 inches of the wrapper to expose
            all the pretty colored wires.
Step 6)  Locate the BIG red 14 guage wire... this is
            unswitched 12 volts going up to the switch.
Step 7)  Locate the Black/Blue 18 guage wire... this is
            the switched 12 volts going to the fan.
Step 8)  Cut the Black/Blue wire.
Step 9)  Splice the part of the Blue/Black wire that appears
             to the front of the bike into the BIG red wire.
Step 10) Rewrap the wiring harness....
Step 11) Put all the tupperware back on.
Step 12) You re done.

NOTE: you may wish to review the wiring diagram in the shop
          manual for your particular year of ST to verify the
          wiring colors.

A future issue of this mod may include installing a switch to:

     1) Switch back to the original wiring.
     2) Switch to the on after shut off setting.
     3) Switch the fan on to warm your hands on cold days.
« Last Edit: January 04, 2013, 03:02:26 PM by Tom Melnik »