High coolant temperature alarm?

[hypophthalmus]

If the coolant temperature spikes, it can be very easy to miss.

I've been thinking about how one might retrofit an alarm to draw to an engine heat well before you risk damage.

An obvious thing would be to wire a parallel connection to the temperature sensor and read it with a microcontroller. But I've read that having a second connection maybe could alter the temperature readings? But maybe you could drill/tap a hole for a second sensor?

Another idea I had also involves a microcontroller, that is somehow triggered by the gauge itself. But I don't actually have any ideas of how to do that.

[ole two wheels]

Good Idea, but why mess with a micro controller, why not just get a car alarm, like for no seat belts on and wire it to your radiator fan hot wire. When it gets hot enough for the fan to come then you would hear an alarm?

[hypophthalmus]

That would be a really easy/elegant way to do it. I think there's too many circumstances where the fan might not come on but the engine will still be hot though.

[MJR]

A simple buzzer wired to the light should be fine if it's loud enough.

[ole two wheels]

Yelp, even better MJR. There is no limit to what us folks can come up with when we pool of mechanical smarts.

[mousejunks]

If the coolant temperature spikes, it can be very easy to miss.

I've been thinking about how one might retrofit an alarm to draw to an engine heat well before you risk damage.

Another idea I had also involves a microcontroller, that is somehow triggered by the gauge itself. But I don't actually have any ideas of how to do that.

If you are using a microcontroller then the temp sensor must not interfere with the bike's temp sensor. In most vehicles the sensor is basically a NTC thermistor (resistance decreases as the temp increases) anything connected to it will change the resistance. As such the sensor for a microcontroller should be completely separate. You could drill a hole, but the other option is attach it to a metal part (e.g. radiator) using heatsink paste and heat-resistant (Kapton) tape.

My simplest idea is thermostat switch on > power on > warning light on. The thermostat should be rated below the overheat temp so the light correctly triggers. If you want to you can also add a relay so it can run a cooling fan.

[CROSSBOLT]

Personally, I think Mac's idea of using the radiator fan switch is the best, simplest and easiest way to go. There is no electrical downside that is obvious and those switches are quite reliable. The only problem I see is a noise maker of any kind might be hard to hear for the rider and the louder it is it becomes annoying. Seems like a good scan of your gages if you have them is in order.

Karl