Charge Light

[davidk65]

I have become involved in helping a friend to fit a new 12 volt alternator to his boat. The original fault was that the charge light started to flicker and eventually did not come at all.

The engine compartment is very confined and you can just get a hand down, with a spanner, to get to the alternator.It was necessary to remove the alternator fixings to enable to get access to the connections, a note was made of these before removing. The wiring around the engine and to the batteries was a bit of a mess and it was difficult to trace out some of the wires. Eventually we removed the alternator and took the unit for bench testing. Verdict, alternator faulty. Replacement alternator obtained and after a struggle it was fitted. The cables to the new alternator where fitted to the correct terminals and corresponded to the connections to the original alternator.

On switching on, "red" charge light on, engine started, light goes out. Voltage at starter battery with engine running 13.75 volts. After about an hour of running the engine it was time to clean up and go home (for me). My friend stayed as he was to move his boat to another mooring. Later, I had a phone call for said friend, having relocated, he is concerned that the charge light has come on and is staying on.

Unfortunately, due to my commitments, I can't get back to check things out for a couple of days and therefore can't confirm any readings and find it difficult to direct my friend over the phone what he could look for our check.

I accept that it is possible the "new" alternator could be faulty but I tend to doubt this. One the other hand I am confident the connections to the alternator are sound and correct.

On the charge light connection at the alternator, there where/are two wires. One wire was for the charge light the other went to a split charge unit which appears to be one of those electronic units used on car/caravans to charge another battery in this case it is connected to the domestic battery. I wonder, trying to diagnose from a distance and to instruct my friend how to use a test meter, if this unit was faulty could it provide an alternative a negative feed to keep the charge light one? Is it possible that the alternator could be charging in spite of the charge light being illuminated?

Any comments or suggestions please.

[Chris Pink]

No, if the light is on the alternator is not charging.

 

As to diagnosis you have to find out what has changed since you left. Which may be something ad simple as he didn't rev the engine enough.

 

I am not a fan of running the split charge relay from the IND terminal and, if you hadn't seen it running would suspect this first.

 

But if was running ok when you left something must be different.

[RobinJ]

On the charge light connection at the alternator, there where/are two wires. One wire was for the charge light the other went to a split charge unit which appears to be one of those electronic units used on car/caravans to charge another battery in this case it is connected to the domestic battery. I wonder, trying to diagnose from a distance and to instruct my friend how to use a test meter, if this unit was faulty could it provide an alternative a negative feed to keep the charge light one? Is it possible that the alternator could be charging in spite of the charge light being illuminated?

Assuming the new alternator is indeed working, there are a number of possibilities!

It is unlikely that any fault on the split charge relay would cause the charge light to illuminate, without other signs, as it relies on the power from the alternator and not the charge light to operate. In order to illuminate the charge light needs a high voltage and a low voltage, and this can occur in two ways; the battery voltage is higher than the alternator - duff alternator; the alternator voltage is higher than the battery - duff battery. Alternatively there is a short somewhere - either side of the charge light?

You need to test the voltages on the batteries - anything less than about 12 and there is a problem.

You need to check the alternator is still working (both sets of diodes are intact).

You need to check the wiring (especially if chocolat blocks have been used- these can rust or create high resistance etc.)

[Keeping Up]

Agreeing with all that has been said above; without some further measurements it is almost impossible to tell what has happened. One possibility not mentioned, is could the fanbelt have broken (the new alternator could be creating more load than the old not-working one) or just be slipping (was it tight enough, or could the mounting bolt be too loose?).

 

There is one condition relating to the split charge relay which can cause the light to illuminate, but it is usually only a dim glow; when the "ignition" circuit is from the engine battery and the alternator is connected primarily to the domestic battery. If the relay doesn't pull in, the domestic batteries which are being charged will be at a higher voltage than the starter battery which is not being charged (and which may be quite low after starting the engine). This voltage difference can be enough to make the light glow, but rarely at anything like full brightness.

[RLWP]

<snip>

 

I am not a fan of running the split charge relay from the IND terminal and, if you hadn't seen it running would suspect this first.

 

<snip>

 

Hi Chris. how have you wired up the split charge relay instead of using the IND connection?

 

Richard

[blodger]

Hi Chris. how have you wired up the split charge relay instead of using the IND connection?

 

Richard

Oil pressure switch?

[Chris Pink]

Hi Chris. how have you wired up the split charge relay instead of using the IND connection?

 

Richard

 

From the ignition on terminal on the switch ie bypassing the lamp.

[Keeping Up]

From the ignition on terminal on the switch ie bypassing the lamp.

 

Doesn't this mean that the relay is pulled in while you are cranking the engine? I would have thought this could result in heavy currents through the relay if the domestic batteries are well-charged and so try to aid the starter, or starting problems if the domestic batteries are very low and therefore take current from the engine battery

[Chris Pink]

good point

Edited May 25, 2012 by Chris Pink

[davidk65]

Hi Thanks for the replies.

I had a brief conversation with the "stranded" boater early this morning ( I am still not able to attend until some time Saturday) and things are as they where i.e. charge light comes on and stays on with engine running.

He confirms that the fan belt is still in place and because it is a single cylinder Saab he can move the alternator fan and it just about turns the flywheel. I asked him to remove the two leads on the "ind" terminal and turn the key. With both leads removed the charge light did not illuminate. I took this to prove that the charge light wiring was not shorted to earth.

I then asked him,in an attempt to establish which of these leads was for the charge light, with the key on and the engine not running, to touch the terminal with each lead in turn. I expected to be told that one or other of the leads (but not both) caused the charge light to come on. The result of this test; the lamp illuminated no matter which lead touched the "ind" terminal.

Without physically checking the wiring I cannot understand how both leads can be connected to the charge light?

My understanding is that the charge light is fed positive and finds a negative via the rotor until the alternator voltage builds up becoming positive hence the light goes out. I would then have expected that the "solid state caravan type split charge unit" would, also connected to the "ind" terminal, have responded to the rising positive voltage at the rotor and would then have operated in what ever way these things do.

I am speculating that this unit may have a fault and when it switches on/over it allows an earth connection to reach the "ind" terminal?

Does this make sense or is the theory all wrong?

[Chris Pink]

. With the lead to the lamp disconnected the lamp should go out therefore there is a wiring fault.

 

Without establishing what this is it is impossible to diagnose the fault. The next stage is to connect a piece of wire from the lamp to IND with nothing else connected and see if goes out when the engine is started

 

You can test the relay by giving it 12v from somewhere else without the engine running.

 

And I've just remembered why I don't like the relay connected to IND because the lamp will light through the relay if IND goes o/c although if the relay is connected to the alternator rather than to the other side of the lamp (as seems common) this is unlikely.

[davidk65]

Having returned to the "stranded" boat, I was able to establish that the reason the battery charge light was staying on was that a second wire, connected to the "ind" terminal (D+) had a -ve feed on it. with this wire disconnected, on starting the engine the light went out and the alternator was charging.

The disconnected wire was used, when the alternator was charging, to provide a +ve feed to one side of the relay coil. The relay was used as a split charge device to connect the domestic battery and the starter battery together for charging.

Removing the relay, I found heavy corrosion between +ve and -ve connections (not the battery leads) to the relay with the -ve tracking across to the +ve putting a -ve feed to the "ind" terminal (D+) which kept the charge light illuminated.

The relay is one that I have not come across before i.e. "TYCO" 12 volt relay. Later, I found a description of this relay on the internet and it has a capacity of 150 amps and is without any degree battery voltage sensing.

As the boat has minimal amount of electrics, and time would not allow me to source another relay, I joined the two the battery leads together.

All now appears right with world of boat electric??

Thanks for all comments.

[Keeping Up]

Excellent, glad you managed to diagnose it OK. Split charge relays often do not have any specific voltage sensing, I'm sure you could replace it with any other GOOD quality split charge relay (but not one of the small Durite ones that tend to melt)

 

Just to confirm - which battery leads did you join together, and how?

[RLWP]

Excellent, glad you managed to diagnose it OK. Split charge relays often do not have any specific voltage sensing, I'm sure you could replace it with any other GOOD quality split charge relay (but not one of the small Durite ones that tend to melt)

 

 

This looks like a good deal:

 

http://www.ebay.co.uk/itm/HEAVY-DUTY-SPLIT-CHARGING-RELAY-100-AMP-/170838493355?pt=UK_In_Car_Technology&hash=item27c6c488ab#ht_505wt_952

 

Richard

[davidk65]

Excellent, glad you managed to diagnose it OK. Split charge relays often do not have any specific voltage sensing, I'm sure you could replace it with any other GOOD quality split charge relay (but not one of the small Durite ones that tend to melt)

 

Just to confirm - which battery leads did you join together, and how?

Alan.

It was the two +ve battery leads that where connected to the main studs of the relay. i.e. the cable from starter battery +ve lug that went via the relay to the domestic battery.

I joined the lugs of these cable together using the only suitable thing available to me i.e. a new a Durite battery isolator switch.

I have now found the time to pries off the cover from the relay, what a mess. It looks as if it had spent a lot of time submerged in water although it was well clear of the wet stuff. It was fitted to one side of the engine compartment and tucked under a overhang of the deck. Perhaps the deck drain had overflowed (regularly) and slopped over the relay as the connections to the relay faced upwards. Downward facing and they would have had some protection from ingress of water. The relay was a charred mess.

This undoubtedly played a major part in the failure of the original alternator. When I had that one bench tested and then stripped they told me the regulator had blown as well as some other damage. I guess we are lucky we did not blow the new alternator.

However; Gods in his heaven and all is good!!

[smileypete]

This looks like a good deal:

 

http://www.ebay.co.uk/itm/HEAVY-DUTY-SPLIT-CHARGING-RELAY-100-AMP-/170838493355?pt=UK_In_Car_Technology&hash=item27c6c488ab#ht_505wt_952

 

Richard

I'd pay a bit more for one of THESE

 

http://www.ebay.co.uk/itm/12v-Split-Charge-Contactor-relay-250-Amp-Continuous-Albright-/300711901744

 

cheers, Pete.

[Keeping Up]

Alan.

It was the two +ve battery leads that where connected to the main studs of the relay. i.e. the cable from starter battery +ve lug that went via the relay to the domestic battery.

I joined the lugs of these cable together using the only suitable thing available to me i.e. a new a Durite battery isolator switch.

I have now found the time to pries off the cover from the relay, what a mess. It looks as if it had spent a lot of time submerged in water although it was well clear of the wet stuff. It was fitted to one side of the engine compartment and tucked under a overhang of the deck. Perhaps the deck drain had overflowed (regularly) and slopped over the relay as the connections to the relay faced upwards. Downward facing and they would have had some protection from ingress of water. The relay was a charred mess.

This undoubtedly played a major part in the failure of the original alternator. When I had that one bench tested and then stripped they told me the regulator had blown as well as some other damage. I guess we are lucky we did not blow the new alternator.

However; Gods in his heaven and all is good!!

 

The alternator gods were clearly pleased with you.

 

Have you instructed your friend to open the switch while the engine is not running? If he fails to do this, as I am sure you realise, the two sets of batteries will remain connected together, so that if your friend flattens his domestic batteries he will also have flattened his starter battery and will be unable to start the engine.