Re: [DML] Fan Fail Light Without Actual Fan Fail

[jwit6@xxxx]

In a message dated 5/13/02 9:06:05 AM Eastern Daylight Time, 
webmaster@xxxx writes:

<< the fan fail module is a 
simple hall effect sensor. It measures the current drawn by each fan and 
if there's an imbalance between the two, the current generated by the 
coil is enough to light the light. Wonderful, if it weren't so badly 
made! I imagine there's a slight imbalance in your two fans - nothing to 
loose any sleep over - but at 13.5v there's enough difference to turn 
the light on.
>>

Thanks for the explanation of the modules hall effect sensor design. Correct 
me if I'm wrong, but it seems the original design intent was to signal a 
failed fan thru a current flow imbalance between the fans, so if both fans 
failed and were essentially open, or the circuit breaker tripped, or the 
cooling fan relay failed, then you would have no fans and no warning light....

You only get a warning light if one is running and the other is not. Correct? 
That seems to be a rare yet survivable situation (with only 1 fan running 
you'll probably be able to make it home). What I did with a rewired Fan Fail 
Module socket and another accessory relay in its place, will tell me whether 
the fans have power, not if there is a current imbalance. The light comes on 
only when the fans are supposed to be running but have no power due to a 
thermal trip or a cooling fan relay failure. 

Jim 6147