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Discussion Starter #1
With plenty of ways MGF coolant pipes can rub holes and burst or leak I conclude fitment of a low coolant alarm is essential.

I would like to fit an alarm system which works instantly on sudden water loss and that gives no false alarms.

To that effect I have puchased a contactless external tank sensor. Having read many posts these devices seem to be best for avoiding false alarms and therefore no need for a delay timer hence a quick response time in the event of a pipe burst.. They also have very low power requirements.

Trouble is I don't want to fit an alarm buzzer or hack up the cars wiring.

Right next to the coolent tank is the high engine bay temp sensor. It has 2 electrical connections.

If this sensor is unplugged the engine bay cooling fan comes on. I guess that one wire is +12v or +5V and the other the feedback to the mems ECU.and a relay drives the fan motor.

My level sensor needs +5-12V, earth and output.

My Idea is to make a small electronics box that the level sensor plugs into and this box intercepts the engine bay overheat sensor wiring. The result a plug and play, no wiring needed factory fit looking water level alarm.

How would it work? you may ask. Well the circuit would need to power itself from that engine bay overheat sensors +12v wire.
It would need a black wire to an earth point. Intercepting the return wire a normally closed micro relay. This realy being switched by the new level sensor. (well that's phase 1)

How would the driver be alerted? Well if the water level dropped and the sensor triggered then the engine bay fan would come on and the engine bay fan warning light would shine. To avoid confusion with a regular hot engine bay condition phase 2 would add transistors to the electronics to flash the warning signal and pulse the fan.

The driver alerted by a regular flash from the instrument cluster engine bay overheat lamp and anoying on / off engine fan operation should know to pull over and deal with the problem.

Advantages of my solution..

1. Plug and play no messy wiring needs adding cutting or joining.
2. Circuit could have choice of contactless, and or existing float sensor inputs.
3. Fits all MGFs and TFs regardless of model or type.
4. Owners with complicated older water level alarms could retro fit and simplify their systems wiring using this box.
5. Flashing dash indicator more alerting than steady red LED on the dash or weird squeak buzzer from somewhere in the back thus to indicate emergancy with more urgancy.
6. Fitting time less than 5 mins very easy to install plugs and plays using quality automotive sensor quick release plugs, Black wire earth ring loop to engiine body earth point, sensor just sticks on.
7. Very low cost.

Anyway I have yet to make this and I would apreciate help from some of the more informed forum members for more information about the MEMS ecu and it's sensor voltages / maximum current etc.

Any feedback would be welcomed, but please avoid these arguments..

I've fitted X from XY&Z and everyone should buy what I got.
I wouldn't fit anything non standard you fool.
Wrong infromation like, you must use a giant power glugging automotive relay.

Do not be alarmed! As a communist I have no desire to capitalise on this idea or interfere with others making fortunes from expensive water level kits. I wish only to to have something that works for me and that others may share or part use any useful discoveries to impove their own solutions or products.
 
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