Mysterious warning lights problem

E

eileandour

Member
Joined
15 Nov 2006
Messages
34
Visit site
I have twin Volvo tamd31s fitted to my boat. For a while now I have been starting the starboard engine first then the port because if I ran the port engine only I got a low voltage reading of 12v. but by starting the starboard engine both voltmeters showed 14v. I figured a new alternator was required. Fitted new alternator today but when I turned the port ignition on the warning lights on both port and starboard were lit and the starboard ones stayed on when both engines were running. Curiously if I start the starboard engine first everything is ok and no warning lights come on. Therefore I cannot run the port engine on its own.
Refitted old alternator but the problem persists. Can anyone suggest what is going on? ( I don't think there is a split charger in the wiring) Thanks.
 
Does the generator warning light come on with just the port engine, and then go out as that engine starts ?

It does seem like the port alternator isn't putting out a charge. If the port warning light has blown there will be no excitation current to get the alternator going at start up. The fact that the fault exists with a replacement alternator would suggest it's not the alternator.
 
Last edited:
This is the confusing thing - if I start the starboard engine first then the port warning lights work correctly and there is no fault, both the warning lights only come on if you start the port engine first. When I fitted new alternator and ran port engine for a short while the voltmeter showed 14v. so I assume it is working. I refitted the old alternator in case the new one caused the problem. There is a battery charger fitted which I will disconnect in case it is interfering. Thanks.
 
Confusing indeed it is.

Sounds like the port alternator is not connected to the batteries. If both voltmeters on the dashboard go to 14V with the starboard engine running sounds like the starboard alternator is charging all of the batteries.
This seems to me a very odd arrangement.


In my limited experience it is more usual to have one starter battery, say, on the port side and one or two domestics on the starboard side (or the reverse). Port engine charges port side and starboard engine charges starboard side batteries.


There may be a link switch to connect the batteries in case the domestic bank is discharged it can be jump started by the other? This should ordinarily not be joining the batteries together.

Could the wiring have been altered from the original arrangement ?

.
 
The wiring has not been altered from original as it left the factory. It is a Rodman and I would have preferred the arrangement you describe but it has worked okay for the 6 years I've had the boat. Each engine's alternator charges the two batteries and if running one engine then it charges both batteries. They are linked in parallel.
 
A clamp meter that measures DC (careful, cheap ones only do AC) would show you where current is flowing in the heavy cables without having to disconnect anything. Might help track down the problem?

Pete
 
This would be my understanding also.

Port Change Port engine Battery

Stbd Charge Stbd Engine Battery

One or other charges the house batteries.

There is the typically a solenoid that can be closed with a switch to allow both batteries to start the engines in case one has gone flat. Start one, crossfeed, start the other.

The Op is convinced that both charge both, so I wonder if there is some solenoid system that joins them when they are both running? If so then I wonder if for some reason the solenoid is only being triggered when Stbd engine starts - leaving the port one open circuit and showing failure as it is connected to nothing?

Does the boat have a wiring diagram?

I would try and chase through what connects to what between the alternators and the batteries if possible. The alternative maybe to call a Rodman dealer and ask. All boats have quirks ( they are Princess now) but if you call Nick or Pete form Boats.co.uk about a Fairline ( they are Princess now) they can tell you instantly how it was built and what connects to what as they have taken them to bits for years.

Also you can test your theory by putting a volt meter across both starting batteries when only one engine is running. If they are connected the voltage will be the same. You could then try the other engine ( that does / does not show the fault lights) and see what that does. If one test shows the the same and one is not then there is a solenoid somewhere that is closing to bring them together.

Good luck .






MartynG said:
Confusing indeed it is.

Sounds like the port alternator is not connected to the batteries. If both voltmeters on the dashboard go to 14V with the starboard engine running sounds like the starboard alternator is charging all of the batteries.
This seems to me a very odd arrangement.


In my limited experience it is more usual to have one starter battery, say, on the port side and one or two domestics on the starboard side (or the reverse). Port engine charges port side and starboard engine charges starboard side batteries.


There may be a link switch to connect the batteries in case the domestic bank is discharged it can be jump started by the other? This should ordinarily not be joining the batteries together.

Could the wiring have been altered from the original arrangement ?

.
Click to expand...
 
I would try checking all the connections in the charging circuit for the port engine.
Looking for loose, corroded or bad connections.

Engine earth, alt positive wires, right through to the battery.

Earth faults especially can give some very strange faults.
 
My guess is that there is a split charge diode which is faulty diode on the port input. I'd trace the cable from the alternators to see if there is one. Wouldn't a split charge diode be necessary anyway if both alternators are connected to both batteries?
 
Jrudge, thanks for your suggestions, there are two batteries linked in parallel which I think both alternators charge. No wiring has been changed from new and previously I could run each engine independently as one would expect. I don't have a wiring diagram but have searched for any split diode charger but can't find one. I have tried to check all the earth connections and all seem okay. I have emailed RBS the Rodman dealers to see if they can help. I thought I might have a duff battery but I checked voltage across both and they seem ok and they were new 3 years ago.
 
Hi,

I have a similar problem (or two actually) with my twin KAD42's. Does the error appear if you only turn on the ignition in the wrong order or do you have to start the engines?

I had a poor connection on the yellow cable on the generator (the one that goes to the generator warning light). Once I fixed it, the error that you describe disappeared.

Now one remains... if I start starboard engine first - the temperature reading on the port engine shows some 15 degrees wrong...

/Christian
 
Hi Mrme, yes as soon as I turn port ignition key the warning lights come on, but all of my connections are tight as I have been swapping alternators. If I turn on stb ignition first there is no problem.
 
You must log in or register to reply here.

Other threads that may be of interest

N
Alternator D+ / 61 Terminal
Replies
8
Views
340
Chiara’s slave
Chiara’s slave

Share this page

Top