My '97 Magna had the following problem:
When I rode on hot days or took long highway trips and the fan started, there was a voltage drop when any other load like the turn signals or the brake light was used. This caused a periodic flashing of the temperature warning light.
Three Honda workshops couldn't fix the problem. They checked out everything and told me this is the way it should be...
Finally a friend found the cause and the fix to the problem:
The analog signal of the coolant temperature sensor is fed to an operational amplifier to switch on the fan and the warning light. The source voltage of the amplifier is not stable enough if other loads (like turn signals) are turned on, and drops for less than a second. The amplifier now detects a higher temperature than the actual one and starts the warning light before it is needed. The light follows the rythm of the turn signal or stays on with the brake light.
This doesn't affect the engine operation and durability, but try to sell a bike with this problem...
Fix:
I put a resistor between the sensor and the amplifier to reduce the negative source of the amplifier. The result is a different voltage curve which prevents the amplifier from switching, but which is close enough to the original curve for a sufficient operation of the fan.
How to do it:
Disclaimer:
This fix works fine for me but your bike can have some other problems. Check the voltage of your battery. It should be between 10.5 V (low) and 13.8 V (full). A broken cell in the battery could cause the same effects as described in this article. If you are not sure about the cause you should not do this modification and ask a workshop.
