Coolant Alarm Driving Me Nuts

[haydn callow]

It would seem so.

[roosmith]

It would seem so.

Sorry Haydn but what are you replying to?

[haydn callow]

MikeWalsalls previous comment

[tallbongo]

No..the internals of the engine being coated would have no effect.

Really. So it knackers the conductivity of the screw, but not the engine, which is also metal?

The relaively small contact area of the screw (compared to the earth contact area) will result in a higher field around it. I guess this could cause preferential coating of the screw.

As none of the earth straps are connected inside the engine that is not relevant...

It's very relevant. I think you'll find that the inside of every component (including rubber and plastic) that is in contact with coolant is electrically connected to the earth straps. It's fundamental to the functioning of the the product you market.

[Mark Elvin]

No..the internals of the engine being coated would have no effect.

Really. So it knackers the conductivity of the screw, but not the engine, which is also metal?

As none of the earth straps are connected inside the engine that is not relevant. And it is such a large lump the currant from the alarm finds a path to earth..

Really, so the fact that the coolant touches the engine & the engine is earthed would mean nothing? Hoe's the coolant alarm getting an earth through the water then. I'm not trying to be awkward, but I can't see how the coolant, being in contact with the engine, would be un-earthed. Makes no difference "none of the earth straps are connected inside the engine" as far as I can see.

[haydn callow]

I think ther might be a misunderstanding....
I thought it was being implied that because the coolant lays down a protective layer which coats the screw and so insulates it electrically that the same would happen inside the engine and so even with a clean sensor screw the currant would not be able to find its way to earth.......what I was saying was that this wouldn't happen as the engine is such a large lump it does not seem to coat it enough to insulate.
Hope that makes sense......
But you can always put a second screw about a inch below the sensor screw and connect it to a chassis earthing point.

[Mark Elvin]

I would suggest that if a clean screw fitted now plays up you have a underlying electrical problem.
Check the voltage at the screw....it trips the alarm at about 2.4 volts

Still having issues. Voltage is 2.65v

[haydn callow]

The voltage at the screw should be max 1.9 volts under normal running conditions......it triggers the alarm at approx 2.7 volts......so there is your problem........the only reason your alarm is going off is because this voltage is being reached...
If fitting a new screw does not cure this problem then the problem has to be a underlying electrical fault or contaminated coolant ( which I doubt )
Suggest you fit a second screw a inch below the sensor screw and connect it with a shorty wire to a chassis earth. Do only use the correct screws, contact Alarm HQ for free replacements .

[Mark Elvin]

Thanks, I've mailed Jo to get a couple of screws sent out, don't think there's an alternator issue as it happens even when the engine is not running

[haydn callow]

The only other thing that might trigger the alarm is a very weak coolant mix......( they don't work in plain water )

[Mark Elvin]

The only other thing that might trigger the alarm is a very weak coolant mix......( they don't work in plain water )

Coolant is OK, I know that for a fact.