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JohnHaines
JohnHaines

Posted: Sat Jun 27, 2015 9:22pm

Post Subject: Warning Alarms

A fault has recently developed on our narrowboat fitted with a Beta 43 engine. On turning on the ignition and starting the engine, the warning buzzer sounds and the red warning light for water temperature comes on - even when starting from cold. Someone suggested that the temperature gauge was faulty;I bought and fitted a new one but it made no difference. At present I have stopped the noise and the light by disconnecting the cable from the back of the gauge but of course I have no indication of the water temperature when running the engine. I know the temperature probe and the gauge are working because after a day's cruising I turn off, reconnect the cable and start the engine. Ignoring the noise for a moment I can see that the gauge is reading about 150 which is what I would expect. Another issue about the warning buzzer (which may or may not be related) is that on starting the engine we used to have the buzzer until we revved the engine up to about 800 rpm or so (presumably to indicate whether charging had cut in). Now it doesn't sound even at very low engine speeds (with the temperature gauge disconnected of course). Any thought on what might be going on please?

Tony-B
Tony-B

Posted: Sun Jun 28, 2015 9:13am

Post Subject: Warning Alarms

First one must understand how the buzzer works so we can eliminate each possibility in turn. I can only talk in general terms becasue I have never had to deal with this fault on a Beta 43. On mots modern engines those buzzers monitor three things. The alternator output (as you say), the oil pressure, and the coolant temperature. Typically the buzzer is fed from an ignition switch controlled supply while the other terminal splits into 3 and runs through 3 diodes (on the back of the instrument panel somewhere, probably in a pack). One diode is connected to the switch (engine) side of the oil pressure warning lamp, another to the alternator side of the charge warning lamp, while the third is connected to the engine side of the temperature warning lamp. This means that the buzzer could be responding to low oil pressure, low/no charge, or high engine temperature. It could also indicate a short circuit to metal between the buzzer/warning lamps and their respective connection on the engine end. The diodes prevent a fault on one system making other warning lamps light up. I would normally suggest that the red light is in fact the charge warning lamp and that there is ether a thin wire fallen off the alternator or, more likely, the brushes in the alternator have worn out but removing the temperature sender wire woudl not stop the buzzer. Likewise disconnecting the "to the sender" wire from the gauge should not stop the charge warning lamp from working. One thing that might is if you disconnected the live side of the gauge that was also feeding the charge warning lamp. In that case the alternator woudl be very unlikely to charge To go further I need to know the on and off alternator charge voltage of the batteries. You may have a separate temperature switch and if that is faulty or if its wire is shorting it would give the temperature symptoms but NOT the charge light ones. I have a feeling that some temperature gauges have an internal contact that illuminates a warning lamp within the gauge if the temperature goes too high but you seem to have ruled a fault out there by changing the gauge and noting the running temperature is normal. If the gauge is controlling an external warning lamp it would need an extra terminal. In general a separate warning lamp for temperature in not normally red. Red is for charge. Typically oil is green or yellow and temperature blue or whichever colour the oil pressure does not display. However it is possible the symbol on the lens of the lamp indicates its use. I would expect a little thermometer symbol. I would need to inspect and test your engine to say much more because of the contra-indicating symptoms but if you email photos (low res. please) of each side, front and back of your engine plus the underside and top of the instrument panel to Tony@TB-Training.co.uk I will see if I can be more specific. Also indicate the general area of your location in case it is close enough for me to visit. However as I am at the end of the Wey at present I fear that is unlikely. Tony Brooks

Tony-B
Tony-B

Posted: Sun Jun 28, 2015 2:06pm

Post Subject: Warning Alarms

Here is a link to a fairly generic wiring diagram http://i50.photobucket.com/albums/f337/Vic43/For ums%202012/Yanmarwiring.jpg (all on one line). Its actually for a Yanmar but the principles are the same.

Tony-B
Tony-B

Posted: Sun Jun 28, 2015 2:08pm

Post Subject: Warning Alarms

The forum software has put a space in the word forum in that web address, please take the space out.

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