Simple circuit with inidicator LEDs
parts:
1 DPDT center off toggle (dual pole , dual throw)
3 resistors (500-1000 ohms, lower rating=brighter led) R1,R2,R3
3 LEDs (yellow, red, green) Ly,Lr,Lg
3 diodes D1,D2,D3
1 auto lighting relay (T86,T85)
1 temperature switch (grounds when on) TS
Toggle has 2 sides, 3 terminals per side T1,T2,T3 (side 1) T4,T5,T6 (side 2) T2&T5 are center terminals. T1,T2 and T4,T5 connect or T2,T3 and T5,T6 connect or nothing is connected in center position
Get a piece of paper to draw the circuit, I'll show the parts.
IG=Ignition +
GRD = ground
Toggle:
T1 T4
T2 T5
T3 T6
Connect T1 and T6 to ground
T1-GRD
T6-GRD
T3 isn't connected
Connect T4 to temperature switch
T4-TS
Connect IG to one side of the relay coil
IG-T86
Connect the other side of the relay coil to T5
T85-T5
Connect IG to R1, R1 to Ly, Ly to T2
IG-R1-Ly-T2
Connect IG to R2, R2 to Lg, Lg to T5
IG-R2-Lg-T5
Connect IG to R3, R3 to Lr, Lr to D3, D3 to GRD
IG-R3-Lr-D3-GRD (diode current flow IG to GRD ->|- )
Connect R3 to D1, D1 to T2
R3-D1-T2 (R3 ->|- T2 )
Connect R3 to D2, D2 to T5
R3-D2-T5 ( R3 ->|- T5 )
When "ON", current flows from IG thru relay coil to T5, thru switch to T6, to GRD turning on relay (and thus the fan)
Also current flows from IG to R2 to Lg to T5, thru switch to T6, to GRD turning on Lg (green led)
When in the other on state or "AUTO", the current goes from T5 thru the switch to T4, then to TS (temperature switch).
When the temperature switch grounds due to temperature, the relay is activated turning on the fan. Also Lg gets turned on when the temperature switch grounds.
The green LED (Lg) will be on whenever the fan is on.
When in the "AUTO" state, current will flow from IG to R1 to Ly to T2, then thru the switch to T1 and then to ground, lighting the yellow LED.
When in the center "OFF" position, the Lr (red LED) is on.
(IG-R3-Lr-D3-GRD)
If the switch is in either the "ON" or "AUTO" position, the red LED is turned off because the current takes the easier path to ground
IG-R3-D1-T2-T1-GRD
or
IG-R3-D2-T5-T6-GRD
So red LED means fan off
yellow LED means fan is in automatic mode (can be running or not)
green LED means fan is on
Sounds more complicated than it is............
_________________ Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

|