Alternator regulator overcharging?

[scr0che]

Whilst running the engine the volts on the control panel suddenly shot up to 15+, the plotter 12v alarm window came up, and the BMV alarm went off showing 15.86v?!

I've had this before, and it turned out a new regulator and alternator refub/service did the trick, about 2 years ago. Surprised to have same issue now.

My question is, I'm 2 weeks from any kind of assistance with fixing this - in the east of Panama. I've disconnected the alternator from the split diode (?) at the alternator end, looks like an 8-10mm cable. This allowed us to continue using the engine without everything going crazy. Is this a safe thing to do? Have I simply stopped the alternator from charging anything, effectively switched it off? Will this damage the alternator by continuing to use the engine?

I'm aware my start (70ah) and bow (200ah) AGM batteries will not be charging, bow used for windlass and thruster. My leisure bank is charged by solar, and I can use that for startup with a crossover switch, my windlass can also be diverted to the leisure bank.

Am I safe to continue for 2 weeks without an alternator charging anything? Is there anything else I should disconnect to safely continue?

 

[Alex_Blackwood]

Whilst running the engine the volts on the control panel suddenly shot up to 15+, the plotter 12v alarm window came up, and the BMV alarm went off showing 15.86v?!

I've had this before, and it turned out a new regulator and alternator refub/service did the trick, about 2 years ago. Surprised to have same issue now.

My question is, I'm 2 weeks from any kind of assistance with fixing this - in the east of Panama. I've disconnected the alternator from the split diode (?) at the alternator end, looks like an 8-10mm cable. This allowed us to continue using the engine without everything going crazy. Is this a safe thing to do? Have I simply stopped the alternator from charging anything, effectively switched it off? Will this damage the alternator by continuing to use the engine?

I'm aware my start (70ah) and bow (200ah) AGM batteries will not be charging, bow used for windlass and thruster. My leisure bank is charged by solar, and I can use that for startup with a crossover switch, my windlass can also be diverted to the leisure bank.

Am I safe to continue for 2 weeks without an alternator charging anything? Is there anything else I should disconnect to safely continue?

Without knowing your system I would give a cautious yes. You should be OK. Your alt. may already be damaged. Is The sensing circuit connected? If so that may limit damage even if the regulator is goosed. Have you checked the sensing circuit to ensure that is OK and not the cause of the fault? If the regulator does not see battery volts it will ramp up the voltage output. In any case it cannot hurt your batteries if disconnected from the diode. You still have your engine . If you use your crossover switch will your solar not charge both batteries as they should be in parallel?
Hope that helps. Again difficult to be precise without knowing the system. Conserve power. Switch it off if you don't need it!

 

[roaringgirl]

If your battery banks are the same chemistry, you could use the 'combine' switch to charge the engine battery at the same time as the house bank.

If you want to protect the alternator from further damage, I would disconnect the low voltage (thin wires) and tape up the ends, then remove the belt (if it doesn't run through other things!)

2 years between rebuilds suggests to me that there's some other kind of problem with the installation: excessive vibration? Heat?

Bear in mind, help is available with alternators pretty much anywhere there are cars.

 

[scr0che]

Thanks for the replies.

I'm at the limit of my knowledge here, not sure what the sensing circuit is, should I be disconnecting it? How would I test it?

Thanks for the tip re combine switch and solar charging my start battery as well, they're all AGMs.

As it's the second time I've seen this issue and I've no idea of the age of the alternator (10+ years) I'll likely replace it once I get somewhere meaningful - Shelter Bay Marina.

 

[Alex_Blackwood]

Thanks for the replies.

I'm at the limit of my knowledge here, not sure what the sensing circuit is, should I be disconnecting it? How would I test it?

Thanks for the tip re combine switch and solar charging my start battery as well, they're all AGMs.

As it's the second time I've seen this issue and I've no idea of the age of the alternator (10+ years) I'll likely replace it once I get somewhere meaningful - Shelter Bay Marina.

The sensing circuit is the alternator regulator reference voltage . This should ideally be taken from the battery. It could possibly be internal to the alternator. If however you do not know what you are looking for it is a bit academic. If your regulator is already goosed it won't matter if it is disconnected or not. Follow either RG's or my original. Bonus if you can remove the alternator drive.

 

[scr0che]

The sensing circuit is the alternator regulator reference voltage . This should ideally be taken from the battery. It could possibly be internal to the alternator. If however you do not know what you are looking for it is a bit academic. If your regulator is already goosed it won't matter if it is disconnected or not. Follow either RG's or my original. Bonus if you can remove the alternator drive.

I have a yellow cable 2-3mm thick going from alternator to battery plus terminal. Should I disconnect that one, if that is the reference circuit? Or leave it in place? Should I expect to see battery voltage if I put my multimeter on the alternator end of this yellow cable from the batteries?

 

[LittleSister]

Over-voltage is/was likely just the regulator gone. Doesn't/didn't necessarily need the rest of the alternator refurbishing/servicing.

Doesn't help your immediate predicament, but if you can just get a replacement alternator sent to somewhere you can pick it up, you can quite likely replace it yourself, and won't necessarily need to find an alternator repair shop.

 

[William_H]

Tricky question as we don't know what sort of alternator set up you have. A simple car type system has a regulator built in to the back of the alternator. This senses output voltage which should also be battery terminal voltage. This will have a wire from engine panel supplying 12v when engine power is switched on to provide initial excitation.
Yes the regulator can fail in a mode of full current to field coil so max charge. When battery is charged it raises the voltage to the point of damaging electronics.
If this is the system you have disconnect the alternator by pulling the plug on the alternator but much safer if possible remove drive belt. if in your travels the batteries get very low it may be practical to reconnect the alternator and run the engine at low RPM. Alternator will run full chat but voltage hopefully will not rise too much as batteries take all the charge. Monitor the voltage of the batteries and stop charging when it rises sufficiently. (experiment here)
As said the system may have an external regulator. Separate small box wired to alternator. This may be set up for voltage monitoring at the battery terminal. (one of the batteries) If this wire becomes disconnected it tells regulator that battery voltage is low and commands full charge. The symptom you see. This will be a lighter wire and should exhibit battery voltage at the regulator end. In any case with this system it should be ok to disconnect wires to regulator to disable charging safely. Again you may want to try connecting again when batteries are low to put some charge in before voltage rises too high. Note a low engine speed will limit charge capability so control the charge.
ol'will

 

[Refueler]

Reading many above ... a simple facts not mentioned :

1. As long as alternator is NOT connected when engine starts and then runs - all will be fine. The Exciter will try to kick alternator into life - but because its not connected to charge - no charge will be generated and exciter will just sit exciting nothing. The only time damage MAY be done is switching OFF alternator while engine is running and alternator is charging batterys.
2. A diesel engine usually does not require any electrical to run ... being a compression ignition engine.

I would have no concern to carry on for a few weeks till possible to fix.

My thoughts are that the regulator has failed on one or more diodes but charge is still connected ... diodes such as these usually drop the voltage 0.3 to 0.7V depending on type ....

I might consider reconnecting alternator for short periods to charge batterys but stop engine ... disconnect alternator .... before approaching full charge.

 

[Alex_Blackwood]

I have a yellow cable 2-3mm thick going from alternator to battery plus terminal. Should I disconnect that one, if that is the reference circuit? Or leave it in place? Should I expect to see battery voltage if I put my multimeter on the alternator end of this yellow cable from the batteries?

Sounds like probably the sensing wire. Yes, if it is connected to the battery and no breaks then you should get battery voltage between the alternator end and -Ve. Don't think it matters if disconnected or not. As others have said won't hurt to reconnect the main charge cable and run engine whilst monitoring battery voltage to give them a bit of a charge.