Indicator Light Glowing - no power??

[RTED]

I installed an indicator light so I will know when the radiator cooling fan turns on and off....works great. However, at 55 - 60 mph, the indicator light begins to glow and gets brighter as the speed increases. The power to the fan is definitely not on because the temp gauge around 190. If I turn on the air, the light glows much brighter. I am assuming that the fan blades are spinning due to the amount of air rushing in and generating power back to the light. What do you think?

 

[Tom F&L GoR]

Did you wire the light across the fan motor or the PCM side of the relay?

 

[RTED]

I wired the light at the fan motor.

 

[Prfgdwrnch]

If a motor is spun, it will produce a voltage like a generator. The faster it spins, the higher the voltage. The airflow at speed spins the fan. That voltage is illuminating your light.

 

[RTED]

Dave....that is what I thought was happening. THANKS

 

[Tom F&L GoR]

The difference would be knowing when the fan was rotating or when the PCM wanted the fan to run. The latter would not glow.