Your Biggest Fan
When It Stops Going Round & Round

Not that this happens all that often but when it does it's a bad thing. Mainly because you only notice it when you're stuck in traffic, it's a hot day and you're just trying to relax, not get steamed.

Suddenly you notice one of two things. The overheat light is on or it simply dawns on you the fan hasn't turned on as it normally would. You can't even remember the last time you heard it. Time to check things out.

1. If you're quite certain the engine was warm enough to turn the fan on you can skip this step. If not then let the bike sit and idle awhile...quite awhile or go for a nice ride and when you get home let the bike idle for a bit rather than shutting it off immediately. No fan? Next step.

2. Make sure the fan is spinning freely. It isn't unknown for a bit of road tar or other gunk to find its way through the screen and keep the blades from turning. Just (carefully, don't punch the radiator) slip a slim screwdriver through the screen and give the blades a little push. The fan spins? Go to step 3

3. Check the fuse. This is a 10 amp (red) fuse under the right side cover of your bike. Inside the fuse box lid is a guide to which fuse protects which circuit. Pop the possible offender out and take a close look. If you have one, use a multitester or a 12 volt test light on the fuse to be sure there is continuity. More than one ace mechanic has looked at a fuse, deemed it good then moved into other areas needlessly. If the fuse is bad replace it. If the bike is under warranty be sure and have the service manager at your favorite shop make note of the problem so there's a history. They may even suggest popping a 15 amp fuse into the box. This isn't likely to cause any damage and it's become 'the' fix of choice for the Vulcan 1600 but if everything is working as it's supposed to, shouldn't be necessary.

4. So the fuse was good, coolant level was correct and the fan spins freely. Well now it's time to put the mechanics gloves on. Ready?

If you look at the bottom of your radiator (engine side) you'll see two gizmos that screw into the area below the cooling fins. The one on the left side of the bike (as you sit on it) is the water temperature sensor, the one on the right is the fan switch. The fan switch is your prime suspect.

To remove the switch you'll have to remove the front guard and rectifier(s) (ok, you 'might' be able to get at it but removing those items makes it a lot simpler).

Drain your coolant ( see coolant change procedure on this fixit page )

Disconnect the connector and unscrew the switch.

INSPECTION & TESTING (I'm quoting from the manual here):

Suspend the switch in a container of oil so the temperature sensing portion and threaded portion are submerged.
Suspend an accurate thermometer in the oil so the sensitive portions are located at the same depth (neither must touch the container sides or bottom)
Place the container over heat and gradually raise the temperature of the oil while stirring for even temperature.

Using a Multimeter, measure the internal resistance of the switch across the terminals at these temperatures. If the measurement is out of range, replace the switch:

Fan Switch Resistance
From Off to On at 212 to 230 degrees F (this direction isn't your problem)

From On to Off at 203-217 degrees F
On resistance should be less than .5 ohm (call it full continuity)
Off resistance should be more than 1 M ohm (no continuity)

In English, when the oil reaches the above temperature the switch should close and you have continuity. Your meter will swing up or test light will turn on.

To re-install the fan switch or install a new one if the old was faulty
Apply some silicone sealant to the threads and torque the switch to 13 foot pounds.

Fill coolant and bleed air from the system.


The hardest part of the project is explaining why the kitchen suddenly smells like burned oil. Maybe you should drag out the old camping stove and do this in the garage.