Bukh sail drive red plastic box for water intrusion alarm

[westerlylad]

Can anyone help with this query please. My sail drive has the rubber double diaphragm water penetration sensor connected to a small red plastic box at the rear of the engine. It has two sets of identification numbers. One is referred to in the Bukh service manual, i.e. 008E5840 and on the other side it has T341ZCD. The manual suggests regularly shorting two of the terminals on the box to test the water penetration alarm. When I do this, my alarm does not function. My query is, can anyone tell me what is inside this wee box and how it is intended to work? And if it is likely to be faulty and resulting in my alarm not working? Thanks.

 

[Rum Run]

I have no experience of this particular device but diagnose faults on industrial equipment on a weekly basis for money.
If the terminals you refer to are on the outside of the sensor, and shorting them does not sound the alarm when it should, I would initially suspect a fault in the wiring to the alarm.
Is there power to the alarm? Is the alarm a buzzer and does that work if powered independently?
Maybe someone who knows about this alarm will answer now I've bumped this thread to the top.........
Good luck with it anyway

 

[westerlylad]

I have no experience of this particular device but diagnose faults on industrial equipment on a weekly basis for money.
If the terminals you refer to are on the outside of the sensor, and shorting them does not sound the alarm when it should, I would initially suspect a fault in the wiring to the alarm.
Is there power to the alarm? Is the alarm a buzzer and does that work if powered independently?
Maybe someone who knows about this alarm will answer now I've bumped this thread to the top.........
Good luck with it anyway

Thanks Rum Run. The sensor which disappears into my sail drive rubber seal is simply a cable ending in two metal rods separated by 5mm. I presume if water gets into the seal, an electrical circuit is completed. The other end of the sensor cable has two spade connectors and is connected to two terminals sticking out of a small red plastic box the size and shape of a standard supermarket pack of paracetamol. There are two other terminals sticking out of the box, one of which is connected to the alternator +ve and is showing 12 volts. The other is connected to a cable which ultimately disappears up to a terminal on the ignition switch I think. The is showing something around 5 volts. There is a further terminal on the box which is not connected to anything. I'm not sure if there is anything interesting going on inside the plastic box, but it seems a bit odd if it's purpose is simply to take 12 volts from the alternator connection and feed it down into the rubber seal sensor which then, if there is water present, would complete a the circuit and send 12 volts up to the acoustic alarm sitting next to the ignition switch. I'll probably have to contact the Bukh people to get an explanation, but I just hoped that someone on the forum would know how this wee box worked.
Thanks again for your reply and bumping the thread up a bit! Cheers.

 

[VicS]

Can anyone help with this query please. My sail drive has the rubber double diaphragm water penetration sensor connected to a small red plastic box at the rear of the engine. It has two sets of identification numbers. One is referred to in the Bukh service manual, i.e. 008E5840 and on the other side it has T341ZCD. The manual suggests regularly shorting two of the terminals on the box to test the water penetration alarm. When I do this, my alarm does not function. My query is, can anyone tell me what is inside this wee box and how it is intended to work? And if it is likely to be faulty and resulting in my alarm not working? Thanks.

It would be worth shorting the lead on terminal 4 to earth to check the warning light and wiring

 

[Rum Run]

For what it's worth, I think that the red box contains a bit of electrickery that is putting a pulsed voltage across the sensor pins, and when it detects a current flow, it switches the line to the alarm on.
Looking at VicS' diagramme, shorting 1 and 2 should result in the alarm sounding and be a test of the red box and alarm.

 

[Yngmar]

Check if pin 1 is also connected to battery negative (possibly via engine ground) and pin 5 battery positive. If so, the box is broken. In the box most likely is a tiny little circuit with at transistor and a relay that amplifies the meagre current from the probe through some saltwater and switches pin 4.

New box costs very silly money, so find yourself some circuit diagram on the internet and build your own or buy a 12V water alarm with relay output.

 

[Yngmar]

Found one that should be suitable: https://cpc.farnell.com/kemo-electronic/m158/module-water-switch-9-12vdc/dp/HK01174

 

[Alex_Blackwood]

Can anyone help with this query please. My sail drive has the rubber double diaphragm water penetration sensor connected to a small red plastic box at the rear of the engine. It has two sets of identification numbers. One is referred to in the Bukh service manual, i.e. 008E5840 and on the other side it has T341ZCD. The manual suggests regularly shorting two of the terminals on the box to test the water penetration alarm. When I do this, my alarm does not function. My query is, can anyone tell me what is inside this wee box and how it is intended to work? And if it is likely to be faulty and resulting in my alarm not working? Thanks.

Not being funny but have you got your panel etc switched on when testing? Obvious. But!

 

[westerlylad]

Thanks guys, this is all great stuff. Thanks VicS, yes I have that diagram and have tried the shorting out as it suggests. That is why I know my alarm is not functioning. And yes, Alex, I have the ignition switched on when I'm doing the test.
I think Yngmar may be close to the solution of my problem with his explanation of what the wee box does, and his suggestion of an alternative to a Bukh replacement may be my best bet.
Thanks again all.

 

[VicS]

Thanks guys, this is all great stuff. Thanks VicS, yes I have that diagram and have tried the shorting out as it suggests. That is why I know my alarm is not functioning. And yes, Alex, I have the ignition switched on when I'm doing the test.
I think Yngmar may be close to the solution of my problem with his explanation of what the wee box does, and his suggestion of an alternative to a Bukh replacement may be my best bet.
Thanks again all.

Have you checked that the panel indication works Ok and that the wiring between the panel and the wee box is Ok? If not , do that before buying the Kemo module. A bad connection somewhere is probably more likely than the failure of the box.

 

[westerlylad]

Yes, VicS, all the wiring seems okay. In quite good nick I would say, although I believe there are some diodes and stuff behind the Bukh control panel that allow the one buzzer to sound along with the appropriate Amp, Oil or Water temp light to come on. This is all working okay as far as the three main alarms are concerned. The only thing is, I don't know if there are any additional diodes that are needed beyond the normal non-saildrive bukh items for the water penetration sensor to trigger an alarm. The maintenance manual does not suggest any replacement or repair actions if the sensor doesn't sound, just that you should check it frequently, which I have, for over ten years now, and it has never worked. You can tell I'm not really worried about it, as the rubber seal appears to be in very good condition, it's just that I've often wondered exactly how it was supposed to work and if there was any cheap-ish fix I could try. I'd like to know how much the replacement Bukh part would be, but I cant find anything on-line about it and I'm too scared to call them!

 

[Yngmar]

I've linked the original part in post #6. It's €235

 

[westerlylad]

I've linked the original part in post #6. It's €235

Thanks Yngmar. I missed the fact that a link appears in red! Well, that's sort of price I expected, but even worse!
I think I'll investigate your suggested alternative now. You have been very helpful with this. Thanks very much.

 

[Alex_Blackwood]

It would be worth shorting the lead on terminal 4 to earth to check the warning light and wiring

View attachment 172791

Could be as VicS says or if not. Disconnect either 3 or 4 which ever you are using and try connecting it to + at 5 and see if that works. It maybe that the action of the sensor switches through the box to put + on terminal 3 or 4.
Edit: Alternatively use a meter and measure between 5 and 3/4 and also -ve and 3/4 with and with out the short between 1/2 and see what you get. I suggest disconnect 3/4 during this test.

 

[VicS]

Thanks Yngmar. I missed the fact that a link appears in red! Well, that's sort of price I expected, but even worse!
I think I'll investigate your suggested alternative now. You have been very helpful with this. Thanks very much.

Could be as VicS says or if not. Disconnect either 3 or 4 which ever you are using and try connecting it to + at 5 and see if that works. It maybe that the action of the sensor switches through the box to put + on terminal 3 or 4.
Edit: Alternatively use a meter and measure between 5 and 3/4 and also -ve and 3/4 with and with out the short between 1/2 and see what you get. I suggest disconnect 3/4 during this test.

Having studied a Bukh wiring schematic and an owners manual I now realise that the sail drive water intrusion sensor does not have a warning light and that it should only sound the audible alarm. Is that correct?

It operates by grounding the negative terminal of the alarm. The high temperature sensor and low oil pressure sensor ground the same terminal via diodes on the diode plate.

If the wring between the the red box and the engine control panel is OK shorting the wire on terminal 4 to ground ( engine block) should sound the audible alarm ( provided the panel is energised of course)

I dont think I would want the sail drive water sensor to sound the audible alarm. I think I would add a warning light and rewire it to just illuminate that.

 

[Alex_Blackwood]

Having studied a Bukh wiring schematic and an owners manual I now realise that the sail drive water intrusion sensor does not have a warning light and that it should only sound the audible alarm. Is that correct?

It operates by grounding the negative terminal of the alarm. The high temperature sensor and low oil pressure sensor ground the same terminal via diodes on the diode plate.

If the wring between the the red box and the engine control panel is OK shorting the wire on terminal 4 to ground ( engine block) should sound the audible alarm ( provided the panel is energised of course)

I dont think I would want the sail drive water sensor to sound the audible alarm. I think I would add a warning light and rewire it to just illuminate that.

Sounds good. I think that switching the negative is pretty common on these alarm systems. Shorting 4 to 1 should also work. I assume that he has terminal 1 grounded?

 

[westerlylad]

This is all great stuff chaps, I'll be trying out all of your suggestions as soon as I can get back to the boat. Yes, Alex, terminal one is grounded on the engine block. Yes VicS, the sensor should just trigger the acoustic alarm with no light, but I agree with you, a simple light warning would be best.