So my “Temperature Warning “ light went on

[Davemn]

Not a hot day.....maybe high 70’s. Maybe 10 minutes of slow riding. Light went off when I got up to speed. Never happened before. Checked coolant and it’s good. Potential problem?

[Bagger John - #3785]

What year and model Valkyrie?

[Grandpot]

Sticking thermostat?

[Valker]

Probably just one of the early sensors. They are known for this. That was the reason for the question about the year. 

[F6Dave]

This was a common problem on earlier Valks.  My light flickered often, usually in cool weather.  The problem was a part called the indicator unit, mounted under the left side cover, which connected to the temp sender, and turned the light on or off.

Later models combined the unit with the sender and ran a wire straight to the light.  They no longer make the old indicator unit.  You can use the new sender on old bikes with a slight wiring mod.

[Davemn]

It’s a 98 standard. Thanks

[Bagger John - #3785]

It’s a 98 standard. Thanks

99% probability that the Indicator Unit failed.

As was posted above, exchange the sensor for a later-model unit and make a wiring change.

My '99 Tourer's Coolant Temp light is also acting flaky, but I have a water-temp gauge installed as a primary indicator - so I know the cooling system is in proper order. When next I have the bike apart for anything I'll swap the sensors.

[indybobm]

This is something I posted back in 2015 about the problem.
Here is how I check the operation of the Temperature Indicator Unit and the Coolant Light on a 1997 to 1999 Valkyrie Standard or Tourer

How the light works. The 97-99 Valkyrie Standards and Tourers have a Thermo Sensor on the thermostat housing. The Thermo Sensor has a wire that connects it to the 2P connector on the Temperature Indicator Unit behind the left side cover and overflow tank.
The Thermo Sensor offers a variable resistance to the Temperature Indicator Unit depending on the temperature of the coolant. When the coolant is 176 degrees the resistance measures 47 to 57 ohms.
When the coolant is 248 degrees the resistance measures 14 to 18 ohms. At ~248 degrees the coolant light should be on.

How to check for proper operation:
1. Remove the left side cover
2. Remove the bolt for the coolant overflow tank and moved it aside.
3. Remove the Temperature Indicator Unit from the holding band so that you can get to the connectors.
4. Disconnect the 2P connector from the Temperature Indicator Unit. It has only wire.
5. Connect a 18 ohm resistor from the only pin on the 2P side of the Temperature Indicator Unit to ground .
6. Turn on the ignition key and the Coolant Light should be on.
7. Turn off the ignition key.
8. Exchange the 18 ohm resistor with a 53 ohm resistor.
9. Turn on the ignition key and verify that the Coolant Light is not on.

This verifies that the Temperature Indicator Unit is functioning properly and that the Coolant Light is not burned out.

Later Valkyries and all Interstates use a Thermostatic Switch to turn the Coolant Light on. The switch is either off or on to control the light.
To eliminate the 97-99 the Temperature Indicator Unit and change to the later Thermostatic Switch do the following.
1, Replace the Thermo Sensor in the Thermostat Housing with the later Thermostatic Switch. You will probably have to change the connector on the end of the wire to attached to it.
2. Remove the Left Side Cover , the Coolant Tank, and disconnect the Temperature Indicator Unit.
3. Jumper the Green/Blue wire on the 2p connector to the Lt Green/Black wire in the 4p connector.
4. The old Temperature Indicator Unit can be removed.

[RWhitehouse]

Also check that the fan is kicking on as it should. Without the fan, the engine can overheat within a few minutes of slow riding or traffic. Let the bike idle warmed up for a few minutes and the fan should kick on. If you have an infrared thermometer, shoot it at the back side of the radiator- mine shows the fan coming on at roughly 210-215 or so.

The early temp control box does seem to be a noted issue with giving "false alarms"- if the fan is running and the rad isn't in the 240+ danger zone, you can pretty safely assume the control box is faulty. 

The earlier system would seem to suggest that Honda may have intended the Valk to have a coolant gauge at one point, as the sensor is a variable resistor that could be used for a gauge. The later system is typical for a "go/no go" idiot light.

[Davemn]

Thanks very much guys. I am humbled by the expertise on this board.