Quote:
Originally Posted by brewtoo
Could be a problem with the coolant sensor PLUG or WIRING HARNESS.
The function of the sensor is to keep the fans off when the engine is cool, not to turn them on when it is hot.
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Kinda' correct...
If one has an erratic or always ON high fan and wants to isolate the problem of ACC default due to open circuit or bad sensor, here is another simple test I came up with and use..
As most now know, you can get the high fan to come ON by simply putting the ACC into default by unplugging the blu sensor..this is just a simple/fast test for high Fan circuit integrity. However , when one has a fan that
always comes on or erratically comes on, it could be the sensor OR poor wires/connection between the ACC and sensor.
So, what I do in that case is to use a 1K resistor [ Radio Shack item/ .25 cents]. Bridge the resistor accross the unplugged harness . That shoud STOP the fan if all is well to the ACC. If that works, then the problem is the sensor or connection at the sensor.
This test simply verifies the integrity of the ACC circuit .I have one made up that plugs right into the harness. Mine also has a sw in-line so I can active the fan by open/close the sw....but you can just stick the ends in there [ bend them over for a good connection..
The 1K is below ACC default or cut-in spec , so that would be the same as a cold sensor............which will be NO fan.
** NOTE:
While we are at an understanding of this sensor/system, I will also say that, for those of you who have done a resistor/parellel bridging of the blu sensor to modify the cut-in spec of high fan to a lower temp trigger of the ACC, it should be noted that the Fan connector unplug/test for high fan verification will NO LONGER work if the bridging was done at the harness plug side....that is b/c, just as in the 1K resistor test, the bridging of the connector for temp modification will stop the ACC from seeing an open circuit when the harness is unplugged b/c the resistor is still in the circuit.. If the mod resistor is on the actual pin side of the blu sensor and the unplugged harness is now open, then the test will still work as stock..
This info is only for those who have chosen to modify the temp sensors values with a parellel Resistor for faster/sooner fan cut-in.....