Low Coolant Level Circuit - Earth Switching Sender

[TWISTY]

Since my first lexus V8 shat itself, I thought I'd install a phew more safety features and gauages. I had a low water temp sender which was meant to be installed when I first done the conversion, but I never got around to it, and I didn't have the wiring for it.

When putting the new motor in, I got the sensor installed into the top of the radiator and told my mate who works at a radiator shop to get the wiring in for me. He said now worries, it'll be about $100 WTF?

So I told him to hang off, I'll try and work it out and wire it up myself. Can anybody give me details on how best to set this up. When the radaitor is full, the sensor is earthed through the coolant. When the coolant level drops, the sensor looses it earth and triggers a LED on the dash, and a buzzer.

I'm guessing you can just get a relay that switches on a output when it looses earth, or is there more to it then just that?

Thanks.

[Toy80Diesel]

yeah, from what I can gather, you need a relay with the five pins. (not four) You use the inner pin to trigger the relay, in this case.

So when its earthed, it remains an open circuit (or no buzzing/lighting) and when its not earthed the thing completes the circuit, turning on the LED/Buzzer.

Shouldn't be too hard to wire, basically if you get it wrong way round, the light would turn off when there isn't any water. Instead of turning on as you would prefer it.

[murcod]

There are a couple of ways you could do it.

Probably the simplest is using a relay powered through the sensor and using the Normally Closed contacts to power the buzzer/light (ie. when relay is energised the buzzer circuit would not be completed; the sensor goes open, the relay is de- energised and the contacts close turning the buzzer on.)

http://www.the12volt.com/relays/relays.asp will give you an idea of what I'm talking about. NO= normally open ; NC = normally closed -> all relative to when no power is applied to the coil.

[-Scott-]

yeah, from what I can gather, you need a relay with the five pins. (not four) You use the inner pin to trigger the relay, in this case.

I know exactly what you're saying, but be careful. I recently found a 5 pin relay which was Normally Open - ONLY. Two output pins were shorted together.

Cheers,

Scott

[spannercrab]

There is a LOT more too it than that. The resistance through the coolant is too great for you to be able to switch a relay coil with it ... you will need some sort of amplifier / comparator to enable you to switch a relay.

You will need to get a hold of a low coolant alarm from somewhere - lot of jap cars have them in as standard, so that would be the easiest option.

The simplest form of it would involve +12v, Gnd, Sensor & Light in/outs ...

It's not just a case of wiring it up - there is a bit missing ...

Even if you *could* trigger a relay directly - it's stil la bad idea as the amount of current you would be dragging through the coolant to the engine block would be enough to put a hole in it ... (the radiator)

[cloughy]

Nothing wrong with a bit of electrolysis ha ha, does the sender have 2 wires if so it should be fine with a relay, but why not just watch your temp. gauge and check your water???

[TWISTY]

Thanks for the reply's!!! I might just spend the $100 and get the wiring kit from them....that way the blame can go back on them if sh!t starts going wrong....

As for why I'm installing it, why not, better to be safe then sorry.....