Yanmar charging light faintly glowing, 13.8V across battery

120 mV from alternator negative to battery negative is a bit too much IMO

Check between your added wire and the engine block assuming the engine block is used as the negative return, and also from the block to the battery.

However I still do not believe that a bad connection in the negative can cause the light to glow. There has to be something causing a significant voltage across the bulb circuit.

On the subject of battery monitor. The NASA ones now give a voltage reading on the starter battery as well as the full monitoring of the house battery. That is normally adequate. The voltage reading gives a pretty good indication of the state of charge which is all you need to know about it ( apart from its ability to deliver the current required to crank the engine)


Found the cause for the sparking when you connected the battery? I'd want to find out why it did that.
The output volts you report from the alternator should give you as good a charging regime as you'll get without a fancy alternator controller
 
Reconnected batteries. Noticed slight spark when re-connecting the starter battery (must be some electronics starting - alternator field? Both the fridge & heater are not connected through the switch panel).

make sure everything is swited off. Disconnect the Negative on the battery place ammeter between -pillar and connection clamp and let us know what your reading is, should be very low ideally nothing. Will not be your alternator as you say its been tested.

could have been a memory and possibly an auto bilge pump or something left switched on?
 
Hi Glenn
I’ve been following this thread with interest, please post when the faults are found.
I don’t think anyone has suggested wiring a ‘jury’ warning lamp, simply connect a wire via a 5 A fuse from the battery positive, to one side of the 'jury' lamp' the other side going to the alternator taking the place of and disconnecting the original wire. With the key switch on, the original lamp should now be off and ‘jury’ lamp on. Start the engine if alls well the ‘jury’ lamp will extinguish, pointing to a fault on the key switch circuit, most likely cause would be relatively high resistance on a termination or contact giving rise to a volt drop, these volt drops are usually associated with higher loads than warning lamp.

If the ‘jury’ lamp glows the fault is else where. At this stage my bet would be an alternator fault!!! But as you’ve had it tested and being declared as working correctly, I’ll give the repair shop the benefit of the doubt for now.

Measure voltage across the lamp and from each side of the lamp to battery negative, recording the results, it might be useful to measure in AC and DC as the output from the alternator is pulsed DC with a ripple current and voltage.

To minimise voltage drops on the negative side of the charging circuit which may or may not be affecting the ‘glow’ temporarily connect a heavy lead from the alternator to battery negative, you should then see a reduction in the 120MV recorded previously, observe the ‘glow’ for change

Similarly you could minimise any volt drops on the positive side by connecting a large cable from the output side ‘B+’ to the positive battery terminal, again observing the ‘glow’

You may want to record the voltages from these tests out of interest for others following this thread, but I think it would be mainly academic and may confuse you even more. As Vic has said its not easy fault finding even hands on you can easily make a wrong assumption

EXTREME CAUTION SHOULD BE OBSERVED WITH THESE LARGE CABLES TO AVOID SHORTS BETWEEN THEM AND IN THE CASE OF THE POSITIVE TO METAL PARTS SUCH AS THE ENGINE BLOCK. AS WITH JUMP LEADS ITS BEST TO FLASH THEM ON INITIALLY IN CASE OF SHORT CIRCUIT

By the way ‘jump leads’ would be ideal for making the heavy lead temporary connections.

If all of the above fails I’m afraid its back to the repair shop, the test may have been given to the apprentice, or the excitation on the test rig may be using a larger wattage lamp or resistor or a combination of both thereby not showing a ‘glow’.

In this case my bet would be that one of the trio diodes has gone open circuit, not giving a positive pulse to match the pulse from the main diode, the lamp would then conduct briefly during this phase through the rotor coil to negative, this would be happening very quickly at frequency /speed the alternator was spinning at, although it might just be visible as a flicker, rather than a steady glow. Under these circumstances the alternator would still give a useful charge but at a somewhat reduced rate.

Michael
 
Update - no update!

Sorry for this, but been very busy at work other commitments so haven't been able to spend any time on resolving the charging problem this weekend (takes 90 mins to drive to the boat).

I've bought a NASA BM1 battery monitor which I'm going to fit ASAP (next weekend). This will answer the two big questions: what's the current drain and what's the charge rate. The BM1 also allows for both battery 'banks' to be monitored for voltage but only one (the house battery) for current.

Thinking about it, I'm pretty certain that there's been additional kit that's been connected to the starter battery -- such as the fridge and heater. If that's the case, I'll be swapping them over to the house battery as part of the monitor install. I reckon that's what caused the spark when the battery was re-connected (the fridge is an Isotherm ASU).

Sorry for taking a lot of time on this -- and thanks for the help & interest!
 
Make sure you install the BM1 EXACTLY as shown in the instructions.

Make no extra connections to the negative terminal of the house battery other than the shunt.
See http://www.nasamarine.com/prodimages/one_battery_wiring1.pdf although it is the diagram for the older version without monitoring for the starter battery

Also note that the white and black wires are connected together at the shunt but not elsewhere

This diagram shows the starter battery but not the monitoring wiring for it.




I reckon in light of all the checks you have done without discovering the cause of the glowing warning light mjf107's comment above "my bet would be that one of the trio diodes has gone open circuit" is a very likely cause. It will require the alternator to be dismantled to confirm it so could easily not have been spotted when it was tested.


.
 
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Without looking at my posts I think I stated it was the trio at fault. As thats the only way that I know of that will allow the higher charging voltage to come out of the alt and cause the light to glow,unless there it a fault between the lamp and the trio. eg, crushed/chafed cable.
 
pampas said:
Without looking at my posts I think I stated it was the trio at fault. As thats the only way that I know of that will allow the higher charging voltage to come out of the alt and cause the light to glow,unless there it a fault between the lamp and the trio. eg, crushed/chafed cable.
Click to expand...
You just said it was the trio gone. Clearly cannot be the whole trio or it wont charge .

MJF107 explains that it could be just one of the field diodes that has gone.

Almost totally irrelevant but I have had the warning light glow with the turn indicators in the car .. but not when all operating as hazard flashers, only when tuning.
Alternator charging normally.

Bad contact on a fuse! You need the vehicle wiring diagram to understand why, but the AA man I asked to check the alternator had obviously come across it before! He knew what it was!
 
I did say a diode about 500 posts ago. When making voltage measurements one has to remember what's being measured. It's a three phase rectified noisy AC/DC waveform. Different meters will measure different voltages and the only certain way is to use an oscilloscope with voltage and current probes or a proprietary tester (not one of the cheap ones). The great thing about those little alternator lights is they rarely mislead, a piece of low technology that works extremely well, like auto thermostats for example.
 
Update - still slow progress

It's a bit like an IT project that's dragging on incessantly.

I've almost completed the installation of the shiny new battery monitor. Had to install a new earth (e.g. neutral) bus-bar to connect all the returns to (except the engine). This meant a whole load of grief with re-routing cables; extending a load, shortening others... The usual boaty kind of grief.

However, the real benefit of this was to sort out the rats nest of assorted cables and the discovery that the main battery cable connecting the two neutrals together was loose.

The other major discovery was a relay in the engine compartment. this has a stack of cables fed off of this going goodness knows where. TBH, I've not a clue what this is doing there nor what it's feeding. I think I'm going to take the opportunity to clean all the connections up on that too.

There's no question that you almost have a marriage relationship with your boat; it's only after several years that you discover how things really work.

I'm hoping to complete the work next weekend so should finally have the all-important current measurements once the monitor's working.

I must post some photos!
 
Crimping battery connections

I need to make up a couple of cables for the battery cables. I've got the 25mm^2 cable and the crimp connectors (they're tight, so definitely the right size).

How should one crimp these monsters? Should I put them in a vice and squish them flat? Or should I solder them (I guess a blow-torch and plenty of electrical solder)? Or is there a special (expensive) tool for the job?
 
Update - battery monitor fitted. Not charging

It's been a while; work's been busy (good - need money to feed the hobby:-), but not enough time to play.

Finally fitted the BM1 battery monitor - including a new negative bus-bar, extending/shortening/re-routing various cables and general hacking. Took the best part of last weekend, so I only managed to run the engine for a short time with the monitor on (definitely don't need an irked SWMBO who was decidedly bored as the shops had shut!).

According to the monitor... it's not charging at all! In fact when I turned on all the internal and running lights it's showing a discharge of 10A. With just the internal lights and navigation equipment on on it's discharging by 3.8A.

I know that everyone's been telling me this for the goodness knows how many threads... Hmm, crow pie, yummy!

So back to what's known. It's not charging. The alternator's been checked. Voltages seem OK.

I shall now go back to the beginning. I'll attempt to measure the voltage and current across the field windings. I'll have one quick check of the resistance between the alternator output and +ve (should be as near as damn it 0). Then it's looking like it's alternator/diodes/regulator, despite it being tested.

Any other thoughts?

One thought from me is that I've had this problem for years! I'm pretty mean when it comes to running the internal lights when at anchor. I had a mysterious problem three years ago where the nav gear threw an alarm despite being under engine for several hours. As we had just arrived in port, we didn't have time to investigate and plugged in as soon as we landed. The problem then went away.
 
GlennG said:
It's been a while; work's been busy (good - need money to feed the hobby:-), but not enough time to play.

Finally fitted the BM1 battery monitor - including a new negative bus-bar, extending/shortening/re-routing various cables and general hacking. Took the best part of last weekend, so I only managed to run the engine for a short time with the monitor on (definitely don't need an irked SWMBO who was decidedly bored as the shops had shut!).

According to the monitor... it's not charging at all! In fact when I turned on all the internal and running lights it's showing a discharge of 10A. With just the internal lights and navigation equipment on on it's discharging by 3.8A.

I know that everyone's been telling me this for the goodness knows how many threads... Hmm, crow pie, yummy!

So back to what's known. It's not charging. The alternator's been checked. Voltages seem OK.

I shall now go back to the beginning. I'll attempt to measure the voltage and current across the field windings. I'll have one quick check of the resistance between the alternator output and +ve (should be as near as damn it 0). Then it's looking like it's alternator/diodes/regulator, despite it being tested.

Any other thoughts?

One thought from me is that I've had this problem for years! I'm pretty mean when it comes to running the internal lights when at anchor. I had a mysterious problem three years ago where the nav gear threw an alarm despite being under engine for several hours. As we had just arrived in port, we didn't have time to investigate and plugged in as soon as we landed. The problem then went away.
Click to expand...
Thats showing full charge from something, 14.3 volts that is. What was happening at that point when you were taking the pic?
Stu
 
Thats showing full charge from something, 14.3 volts that is. What was happening at that point when you were taking the pic?
Click to expand...
Quite.
The voltage indicates that the alternator is generating OK and at 14.3 the battery must be charging!.

What readings do you get on the monitor with no loads switched on.

Check the installation of the monitor It must be istalled exactly as decribed. Importantly there must be no connection to the battery negative other than the shunt and there must be no connections to the shunt other than the yellow, white and black wires to the monitor and the main connections to the battery and the negative busbar

scan0058.jpg
 
On reflection it seems likely that the monitor is only recording the discharge current and that your charging current is bypassing the shunt.

You must have the negative connection from the alternator still going directly to the battery negative.
 
As the poster who first replied said "check all your connections"
In the 1970's my first car with an alternator was a Ford Capri. This did exactly the same thing and several Ford garages failed to find the fault. A local motor engineer found the problem, a fuse which was not making proper contact with the fuseholder, hence fooling the system into appearing not to be charging
 
The last thing that hasnt been mentioned which does come up on this alternator is the slip rings which are stainless get a kind of glaze build up. try some wet and dry on them.


steve
 
VicS said:
On reflection it seems likely that the monitor is only recording the discharge current and that your charging current is bypassing the shunt.

You must have the negative connection from the alternator still going directly to the battery negative.
Click to expand...

I think he's right. ;)

My only other thought is that the shunt is reversed. It would be pretty obvious if that was the case, though, as it would give 'charge' readings when the engine was not running. Surely not? :rolleyes:
 
Playtime said:
I think he's right. ;)

My only other thought is that the shunt is reversed. It would be pretty obvious if that was the case, though, as it would give 'charge' readings when the engine was not running. Surely not? :rolleyes:
Click to expand...

My first thought actually but then I realised he showed a 10 amp discharge with lots of stuff switched on and a 3.8 amp discharge with less switched on.


Sadly installing the BM1 has produced a whole load of new problems and has got us no nearer solving the mystery of the glowing warning light. On that I go along with the suggestion that a failed field diode might be the cause.
 
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