Where does the computer get temp info?
Thread Starter
Racer
Joined: May 2013
Posts: 297
Likes: 0
From: Stowe VT
Where does the computer get temp info?
On my 86 ,i understand the aux coolant fan looks to the thermo switch for info to turn on, and i also understand the main fan gets its signal from the computer, but HOW does the computer know when the high temp is reached ? What gives it its info? Im a newbie thanks for the help.
Team Owner
Joined: Sep 2003
Posts: 25,381
Likes: 2,735
NO - not really! The aux fan has a switch of it's own and it's located between spark plugs number 1 & 3 (LH/drivers). Your car actually should have a total of three switch/sensors. The gauge (rear right cylinder head)the sensor for ECM which also controls cooling fan and the aux fan.
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
to add to the confusion...
the series of temp senders are also all unrelated and operated in a different way.
gauge sender is a variable resistor...
the main fan is similar BUT this one communicates with the ECM which then manages an internal ground to give the main fan a closed circuit. This fan ALSO has input from the a/c system that uses a high pressure switch that closes when the system pressure builds high enough and this completes a circuit for the main fan...as well.
Then there is the aux fan that is the simplest of them all. There is a switch that's set at approx 238 degrees (iirc) and when that temp is reached, the switch itself grounds, completing the circuit for the aux fan to run.
The drawings in the FSM are most helpful when trying to learn/understand this very complex electrical system.
the series of temp senders are also all unrelated and operated in a different way.
gauge sender is a variable resistor...
the main fan is similar BUT this one communicates with the ECM which then manages an internal ground to give the main fan a closed circuit. This fan ALSO has input from the a/c system that uses a high pressure switch that closes when the system pressure builds high enough and this completes a circuit for the main fan...as well.
Then there is the aux fan that is the simplest of them all. There is a switch that's set at approx 238 degrees (iirc) and when that temp is reached, the switch itself grounds, completing the circuit for the aux fan to run.
The drawings in the FSM are most helpful when trying to learn/understand this very complex electrical system.
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
As you can see in the circuit diagram below from the FSM ( that you should own ) there is no connection anywhere between the main and aux fans,
except they both get their power from the same source
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