Coolant alarm problem

[gh68]

Hi all,

My first post here, I hope you can help me.

We bought our diesel bongo at the end of last year and I'm just starting to sort a few issues out on it.

First thing I noticed when I bought it was that it had a Haydn coolant alarm fitted but it appeared to be dead.

I found that the fuse in the feed to it (feed from the RH blinds on the fusebox, blinds are working) had blown.

This seems a bit strange as I can't find any issues in the wiring to the alarm that would have caused a short.

I replaced the fuse and got an very brief sound from the alarm (less than a second) and a quick flash from the LED, bit then nothing. Switching on the ignition doesn't or disconnecting the sensor wire doesn't cause the alarm to sound again.

Removing the fuse and re-inserting causes the brief sound/flash each time.

Does this sound as though the alarm is damaged/faulty?

(The alarm is a round cylinder type with Haydn/phone number on it, not the square type currently advertised.)

Also, while checking this I checked the voltage across the header tank screws and it showed 0.8v even with the alarm fuse removed. Does this sound right? I've never checked before but why would there be a voltage across these screws with no power to the alarm? Does this point to a short somewhere?

Thanks

[g8dhe]

Welcome aboard!

Do you have a leisure battery fitted ? Often the blinds are transferred across so they are not controlled by the ignition switch, in which case the situation your getting is correct, you would normally have the supply to the alarm connected to a circuit controlled by the ignition switch typically middle row righthand end using a Piggyback fuse holder https://www.ebay.co.uk/sch/i.html?_from ... e&_sacat=0

[gh68]

Thanks Geoff,

I don't have a leisure battery but I do have dual starter batteries with a by-pass circuit on blinds, interior lights, radio and mirrors. So that is definitely a problem because the coolant alarm will be live all the time as you say.

So I see, as soon as I replace the fuse, the coolant alarm is instantly and permanently live.

I'll move it to another circuit and try it. Is that very quick momentary beep and flash correct though? From what I've ready it seems it should be 1 second or more and wouldn't the alarm sound if I disconnected the sensor wire regardless of how its powered? Still seems faulty to me.

[g8dhe]

Yes its a self-test that Haydn built in at switch on to assure you that the electronics element is working, it can't obviously test the sensor screw(s) themselves but you will know that the electronic elements are working.

[gh68]

Ok thanks, I thought that disconnecting the sensor wire would simulate a low coolant situation and trigger the alarm, I suppose I'll have to actually remove some coolant to test it then after I've moved it to an ignition-live circuit.
Thanks for your help.

[g8dhe]

Yes if you disconnect the sensor and isolate its connection then that should set the alarm off. It works by passing a very small current thru the coolant to the metal pipework that is earthed, so isolating the connection at the bullet connector should set the alarm off.

[gh68]

It doesn't sound the alarm when I disconnect the sensor wire that's what I was saying.
I get one bleep/flash when connecting power but nothing if I pull the bullet connector.
So does that indicate that the alarm is faulty?

[g8dhe]

Yes in that case hopefully you can contact Haydn who is often still on the forum.

[Ian]

If you can't get hold of Haydn (he's retired) try Jo who now runs the business. Her contact details are on www.coolantalarm.co.uk

[gh68]

Thanks for your help