Low Coolant Alarm - How to fit one on the cheap.

Hi David,

I just saw this post of you. Did not saw it earlier.

It took me some time with my morning coffee to figure out how this timer works in all situations in accordance to your descriptions.

Actually, you should not move LED and buzzer from NC terminal to NO terminal. You need to leave them on NC terminal. NO and NC terminals have nothing to do with how your source of signal - your switch in the expansion coolant bottle. NO and NC terminals just show how timer relay works on which terminal.

In accordance to your setup which worked you need to revert your source signal from expansion bottle to work how it worked before in previous bottle. You can do that by adding one plain relay in the part of circuit from your expansion bottle switch to T2 terminal.

I will draw you diagram later in the morning to show you how to connect it.

Here is the drawing how you can connect new float switch with relay to your timer:



I will also use this space to explain how this timer circuit works:

Outputs are taken from either NC (Normaly Closed) or NO (Normaly Open) terminals. Whatever signal (earth or power) you put on C (Common) terminal that signal, is passed on NC terminal. NO terminal is empty.

Now you have timer inputs. You cen either use earth (for that you must use T2 terminal) or power (for that you need to use T1 terminal). So when you put signal on timer, timer is alerted, but still did not started to count time. You need to release the signal from timer input in order for count to begin.

However as soon timer is alerted relay changed its position from NC to NO and now you have connection from C to NO, and will remain in that state until you drop signal from T terminal when count will start and when count ends, NO terminal will be empty and NC terminal will again pass signal from C terminal.

Now, signal from C terminal will remain on NO terminal as long as you hold signal on T terminal. When you release signal from T terminal countdown begins, but if you return signal to T terminal before countdown ends it will stop countdown and relay will remain in state where it passes signal from C to NO terminal.

Thankyou, very much.:yesnod:

It all becomes clear after your explanation.

Now where did I put that spare relay?

I got hold of a tank from a ZR Streetwise a while ago that has an internal float.
I ran a permanent live through a bulb fitted in the "cat overheat" warning on the dash and on to the tank and earthed the other side.
I get a warning light on the dash when the float drops too low but as there is no audible warning I don't an annoying buzz.
The light does flicker when driving hard but that just confirms it is working.
And as it is permanently live I know the coolant is too low as soon as I get in the car, I'd rather a a flat battery than an empty cooling system.

Interestingly, I took the car down to a body shop for some titivation and the alarm, still wired incorrectly, only went off once on a sharp lefthand turn. Stayed on for the delay time and reset.
Once I get the car back I'll get the relay wired in.

Source of the coolant leak


You can see here where the reinforcing sleeve has dropped down allowing the plastic above to fracture.