I have two temperature switches; one is in the engine the other is in the radiator.
Both switch to ground. Here’s what I want to do: - I would like one warning LED green when the ignition is on, yellow when the engine switch switches the fan on and red when the rad switch switches. This way I can understand when the fan is running and when the fan cannot cope with the heat generated. So if I was to use a three colour LED red, green & yellow either common cathode or anode, three wire device.

But how should it be wired? I guess it will need a bit of logic as: -

with the ignition on(+ signal) – LED green enabled
Sw1 (engine tempswitch) on & Ignition (+ & - signal) – LED green and red enabled to give yellow?
Ignition, Sw1 and Sw2 on ((+signal,- signal, ,- signal) – LED red enabled green disabled

its far more simpeler if you use a micro controller

its overkill i know.

but at least this kind of problems don't exist with them.

a mikro chip is a small computer.

Sow we feed it with 5volts..

taken from a reg.

then we have 3 inputs

and 3 outputs

Tks

Thats what i thought but then I'd need a program etc! I'm willing to learn though so where do i start?

you want i can send you a sheme

wich you need to make up,

the program en the microcontroller are only interesting (to learn) if you gonna use it more times.

if you are in big need i can send you a programmed chip wich is ready for the job.

Wy you don't make this with 2 temp senders?

then you would know exactly what the temp is in the head and in the rad.

also while driveing etc. etc.

problems could be settings etc.

Do you have a laptop?

Tks

I would like to see a scheme, I could then make it up.
A programmed chip would be very handy.

The reason I chose to do it this way is because I don’t have much space and using two temp senders would require someone to make a decision! A red LED is really easy to understand! I will have a engine temp gauge as well but there’s nothing like a big red LED to tell you something is wrong!!
And I do have access to a lap top / PC.

Deleted previous posts as I realised we need more info on the wiring of this system:

1)Are there two fans (i.e. one per switch) or one?
2)If one, are both switches wired to it?
3)Is the fan(s) wired to a permanent supply or is it switched with the ignition?

Connect SW2 across the green LED so when SW 2 made, green is shorted and only red is on ?

yea that would be the simple option!