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MarkJ · 26-02-2009, 04:29

Hi Folks J

Damn boats are weird!

Starting the engine to charge the batteries tonight the voltage wouldn’t rise at all to its normal 13.3 to 13.6 volts.

Tried restarting with a few revs to ‘excite’ the alternator.
That didn’t work but often does when I have this problem.

I checked the charge on the engine battery and that was charging fine at 14.6 volts (that seems high) but there was nothing on the house battery just 12.2 v

I cleaned the terminals of the batteries and all the stuff inside the engine room but still didn’t start charging.
Finally started charging but only at 12.99 to 13.1…

I thought it sounds like a dirty connection somewhere but I don’t know where the likely thingo to clean is!

The regulator is internal to the alternator.

If the engine battery is charging but the house batteries wont where should I be looking?

What else should I be doing? (running back to Momma?)

Please use simple language in your reply of I will come around and steal all your beer

Thanks for your help

Mark

DeepFrz · 26-02-2009, 06:02

How is your alternator connected to your batteries? Does it go from alternator to house bank or alternator to starter battery? How are the two banks connected together (Echo charge or switch)? Where does your alternator sense the voltage, at the battery or at the alternator? Answering these questions should point you in the right direction.

**Ex-Calif** · 26-02-2009, 07:02

Mark - If I recall your system description from another thread you have a basic alternator with internal regulator, a 1-2-both switch and 2 batteries. or maybe 1 start and 2 house. If so...

I assume you start on 1 and then switch to both for charging.

I might suspect the switch itself. One way to check is to swap the house and start battery cable positions and see if the fault transfers to the other bank.

r.furborough · 26-02-2009, 07:16

Just a quick thought, if you have something drawing sufficient load on our house batteries then that wouldn't that potentially drag down your charging voltage. Check that all house circuits are isolated and check the voltage again. If you have 12V refrigeration sometimes this is directly connected via a fuse to the battery and not through a breaker.

MarkJ · 26-02-2009, 13:11

Thanks everyone for the responses.
1) No other draw on.
2) If I knew the answers to DeepFrz and Ex-calf I would prolly know what I am talking about

I can't see how its all connected. It all just wires. When I wake up properly I'll get back in there

Mark

donradcliffe · 26-02-2009, 14:01

Just take your trusty digital voltmeter, connect the black wire to a good ground, start the engine, and start at the alternator output (the fat wire connected to the insulated terminal). Measure the voltage at each connection as you trace the wire towards the house battery and somewhere you will find a drop from 14+ volts to 13 or less. Your problem will be between the points where the voltage drops the most, and could be a wire, a terminal, or a switch. It may also be hot to the touch, as the faulty connection will generate watts equal to the amps times the voltage drop across it.

Sandero · 26-02-2009, 14:33

Can you describe the entire charging system? Do you have monitor? What does it read?

MarkJ · 26-02-2009, 16:05

Thanks Don,

I have tried to follow what you have said. The connections are very difficult to see and the cables seem to disappear into bundels.

The thing in the photo that I have arrowed is hot when the engine is on.

When off and I conect the right side large red cable it shows 13.6 volts. But the large red one on the left shows 12.6 volts.
Should they be the same?

When the engine is on and charging 13.94 Right and 13.19 Left
Its too hot to touch after 10 mins charging.

What is this little cylinder? Is it the problem?

Thanks for your help.

Mark

MarkJ · 26-02-2009, 16:12

By the way, the blue and great cables that are in the white bundle at the top appear to come from the alternator.

Is the discolouration on the aluminium cylinder from the heat? If so its been corroding for a long time.

Mark

r.furborough · 26-02-2009, 16:29

That cylinder is a relay along with the small relay (black plastic square box) I think it forms a Split Charge System. If I am correct, the large relay is switched by the small. The large relay then switches the charge from one battery bank when charged to the other. I have a circuit diagram of this type of system if you are interested.

Bob

MarkJ · 26-02-2009, 16:59

Quote:

Originally Posted by r.furborough

That cylinder is a relay
Bob

Hi Bob,

Thanks for your help

A circuit diagram doesnt help my puddle-brain

So if the large relay is hot we could assume its bung and I could get a new one at the Auto shop?

Mark

DeepFrz · 26-02-2009, 18:03

That heat is a problem. It's caused by high resistance contacts inside the relay and has discolored the cables and damaged the heat shrink on the left hand cable. The voltage should be almost identical on both sides. You have a dangerous situation as it could very easily cause a fire. The large relay should be replaced immediately.

I think that the two relays are (probably) acting as an "Echo Charge" device.

DeepFrz · 26-02-2009, 18:12

Take a look at the two fuses on the left side of the picture. The wires are connected to the same side. The current isn't flowing through the fuses at all and therefore the wires connected to the fuses are not protected.