Bongo Fury

Hi, Help please

I have one of Haydn's excellent water alarms and for nearly two years now I have had to disconnect it when driving due to a very annoying gradual whining turning into full alarm over time (perhaps 5 mins). It works fine when first connected/engine first started but gradually starts to whine as explained above, so is fine for an instant test but not to leave connected. I believe I have narrowed the problem down to some kind of voltage or charging problem.
Obviously I would like it to be connected 24/7 but due to the whine it's not possible.

So my question is to all those 12v electric experts out there, how do I diagnose the problem?

Here are some points,
- I have a leisure battery fitted with one of the willinton kits
- the alarm neg wire (from the screw) is directly connected to the main battery negative and the other negative from the unit is to a good earth on the dash.
- the alarm pos wire (from the screw) runs through the body and into the unit as it comes fitted.
- the positive from the main unit is connected to the main battery via a spare fuse (courtesy of the willinton kit)
- I have tried connecting the positive directly to the main battery to ensure a good connection/circuit.
- adding to the electrical load when the alarm starts whining only increases the pitch of the alarm and brightness of the bulb until eventually it gets to full alarm and brightness
- the water level is fine and there are no leaks
- when the alarm starts to whine or is in full flow, shorting the two screws (in the expansion tank) stops the noise and when 'unshorted' the noise starts again gradually as above
- I have recently replaced the thermostat and used 50/50 coolant to water so the 'strength' is correct
- the output of the alternator is 'good'
- the leisure battery charges OK and has a 'good' voltage
- the main battery is only 12v when according to my cheap battery meter should be 12.4v to be 'good'
- the main battery is at least 2 years old but more than likely older as it is covered in Jap writing and no English and we are the second owners.
So am I missing something obvious? Should I replace the battery? is there a way to test the water alarm , although it has already saved me when a pipe leaked and worked correctly then! .......
over to the experts.......
oh and ps rather than ask Haydn directly I thought I'd offer it up here for a discussion and to possibly benifit others with the same issue in the future.

Not 100% sure but i think the problem may be that the negative from the screw that goes into the coolant tank should be connected to the main body of the car negative, and not direct to the negative on the battery it may be picking up fluctuations from the battery being charged/discharged.
The main wire from the alarm should be connected to a switched live (power on when ignition is switched on) not a permanent live.
( now i stand to be corrected on this ,like i said not 100% sure that's the problem)

Thanks for the reply, confirmed, the pos is a switched live and fairly sure the neg came with the connector already on to connect directly to the battery terminal, but not certain that's correct,
anyone got one handy they could check?

Ive fitted one or two and have never connected the earth direct to the battery, always to the body of the car. it may not make any difference but worth taking off the battery and repositioning it to the body.

Ok, Back in 5 mins

Forgot to say, gently unscrew the screws from the coolant tank (one at a time)and give them a clean with a wire brush.
Nearly two years in the coolant ,just may need a clean to give better contact with the coolant.
(come on Haydn am i on the right lines here or just blowing smoke)

I'd agree with you there Dave At 12v, your starter battery is a bit low there too Miker, the coolant alarm is very sensitive to such things.

What has already been posted is sound Dave, I'm sure Haydn will pm Miker rather than discuss here......
My alarm has done that before.....I just checked the connections and all was well.....if it does it again....

Right, swapped the wire to the body and after a quick test and all lights, internal fans, indicators etc going, it seems it may have cured it!
I thought by connecting directly to the battery I was using the best earth available but seems not! Yes, my thoughts on the battery too Kirsty, I'll keep an eye on it and replace when I can afford to.
I'll report tomorrow if it doesn't work longterm, thanks for the help, what a great forum!!!

It does sound like a poor connection

Also I know its not unusual to chirp on a cold morning and I noticed this morning that it coincides with the glow plugs coming on, as they do when you start in the cold

True, the neg to the battery was the one connection I was happy about! oh well.......

It really should make no differance if you connect to the battery or vehicle body. All that has been said so far is good sense....12 volts at the battery is more or less flat....(could be the problem) what does the battery read with engine running.....the fact that it now seems to be o.k. after moving the earth ..points to a bad earth connection.

If you are only reading 12 volts with the engine running your alternator is shot or not connected !!

Yes, that makes sense, engage brain before typing.
Alt is fine as leisure batt was def' good on both readings and my cheap meter has a alt light which was green. Taking the bongo to a garage to get a 'proper' load test done on the main battery today.