will this fan switch work with my pcm? [diagram]
03-08-2012, 07:59 PM
#1
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will this fan switch work with my pcm? [diagram] here is the original diagram, uses a dual fan pcm output and a single fan/2 speed ford tauras electric fan
DIAGRAM #1
i want to add a switch so i can run my electrical fan manualy at the "low speed" setting, mainly for track days - so i can leave it running between runs. i chose low versus high, just so i wont have to worry about battery drain.
could sending a positive current from the battery[while the vehicle is off] have an negative affect on the pcm? would i also need to jump a positive current from the battery to the "12+ Ignition" aswell for the fan to turn on/while the vehicle is off
DIAGRAM #2
REMOVED
btw im using two Tyco 12V 75A relays
thank you
DIAGRAM #1
i want to add a switch so i can run my electrical fan manualy at the "low speed" setting, mainly for track days - so i can leave it running between runs. i chose low versus high, just so i wont have to worry about battery drain.
could sending a positive current from the battery[while the vehicle is off] have an negative affect on the pcm? would i also need to jump a positive current from the battery to the "12+ Ignition" aswell for the fan to turn on/while the vehicle is off
DIAGRAM #2
REMOVED
btw im using two Tyco 12V 75A relays
thank you
Last edited by SIKHS 5; 03-09-2012 at 03:36 PM.
03-08-2012, 08:20 PM
#2
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also would the pcm being always sending out a low fan/high fan signal even if the ignition is not armed?
if so:
wouldn't this work?/would also shut off when it reaches a low enough temp. (whatever temp. shutoff is assigned in the pcm)
DIAGRAM #3
REMOVED
if so:
wouldn't this work?/would also shut off when it reaches a low enough temp. (whatever temp. shutoff is assigned in the pcm)
DIAGRAM #3
REMOVED
Last edited by SIKHS 5; 03-09-2012 at 03:36 PM.
03-08-2012, 09:43 PM
#3
TECH Senior Member
No on both diagrams.
Wire the switch between the right-hand relay pin 85 and ground (i.e. in parallel with the PCM's low fan control (green in your diagram)).
The PCM switches the relay to ground to run the fan.
Wire the switch between the right-hand relay pin 85 and ground (i.e. in parallel with the PCM's low fan control (green in your diagram)).
The PCM switches the relay to ground to run the fan.
03-09-2012, 04:56 AM
#5
TECH Senior Member
No worries.
The relay coil is connected internally between pins 86 and 85...
pin 86 is connected to 12V;
pin 85 is connected to the PCM;
to run the fan, the PCM completes the relay coil circuit to ground (the PCM pin sinks current to ground);
to stop the fan, the PCM opens the circuit (the PCM pin becomes high impedance and the circuit floats).
The relay coil is connected internally between pins 86 and 85...
pin 86 is connected to 12V;
pin 85 is connected to the PCM;
to run the fan, the PCM completes the relay coil circuit to ground (the PCM pin sinks current to ground);
to stop the fan, the PCM opens the circuit (the PCM pin becomes high impedance and the circuit floats).
