I took the alternator to the shop and had it tested and rebuilt, tested, took it back and installed it. It still had amperage flowing back when everything was off. I called the shop and went through the connections. I returned it and they checked it again. That was when they told me that it was their policy that if a unit has been customized they put it back the way it came in. Since the alternator was last changed in 2017 I presume the PO may have been responsible. The shop changed the regulator to the one that matched the alternator and life is good. I am calling the little box attached to the back of the alternator the regulator. I am out of town again so I can’t provide the model number.
Alternator amperage question
- Thread starter Tkman
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This is a picture of the back of the new alternator. The silver “box” is what was replaced.
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That is a pretty and shiny new alternator.
Based on your post “life is good” that you got your engine up and running again. Good for you.
As a query, your picture shows a red wire. It appears to have a black scorch or oil mark and a bend as it was stretched during install.
I would be concerned about chafing of the wire.
Based on your post “life is good” that you got your engine up and running again. Good for you.
As a query, your picture shows a red wire. It appears to have a black scorch or oil mark and a bend as it was stretched during install.
I would be concerned about chafing of the wire.
That’s the 10 awg power wire from the B terminal to the panel. It’s unfused and a known fire hazard.
TJ -
there’s several things you can do to improve safety and starting and charging. See the last article on the list here
https://groups.io/g/Catalina30/wiki/home
TJ -
there’s several things you can do to improve safety and starting and charging. See the last article on the list here
https://groups.io/g/Catalina30/wiki/home
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Would a 50 A fuse be right or should I go smaller on the #10 red. The discoloration is just grime from electrical tape adhesive.
The link to the wiki site didn’t work, btw.
The link to the wiki site didn’t work, btw.
Start with a 30. You might need to go higher to prevent nuisance blow due to glow plugs.
Does this work?
https://groups.io/g/Catalina30/wiki/home
Of course, use a 10 awg tinned ATC with weathertight fuse holder.
Does this work?
https://groups.io/g/Catalina30/wiki/home
Of course, use a 10 awg tinned ATC with weathertight fuse holder.
Size the fuse by the wire size and location. But you’ve never said what size alternator you have. You may find the wire too small. The fuse would go on the battery side of the cable.
Les
The alternator is a 51A variety. The link now works. Thank you.
I am planning on re-installing the ammeter in the engine compartment between the alternator and starter solenoid using two #10s just for occasional amp readings. I built a bracket that can be mounted to the plywood of the seating area out of the way but viewable. What do you think?
Tom
I am planning on re-installing the ammeter in the engine compartment between the alternator and starter solenoid using two #10s just for occasional amp readings. I built a bracket that can be mounted to the plywood of the seating area out of the way but viewable. What do you think?
Tom
Les:
The fuse is needed within 7" of the "B" post, on the 10 ga wire to the panel.
You do NOT want to fuse that wire to its capacity -- the article explains why.
The capacity of the alt has no bearing on the fuse size or that wire gauge.
TK:
On the ammeter, we have a saying - YBYC - "your boat, your choice" What you need to do to improve the situation is run a heavy (#8 or #6 or #4) AO cable to minimize charging V loss, run a heavy alternator frame ground (match the AO cable), get rid of the poor harness negative connection on the exhaust manifold, etc etc etc. The last thing I would worry about doing is putting in a shunt and ammeter but I have a clamp-on meter that I can check amps whenever I want to.
Thanks. I just read through the harness/wiring primer and have stuff to do on my return. I appreciate everyone’s input. Happy sailing!
You should probably use a much heavier gauge wire for the B+ terminal to battery. You have a non-remote sensing regulator, and with 10AWG for any distance, and a fuse, you will drop enough voltage in that connection that your batteries will be chronically undercharged. I would go with 4AWG minimum. You can then increase the fuse up to the wire's max., certainly above your alternator's output rating.
I recommend against running the charge wire up to a panel-mounted Ammeter and back.
I recommend against running the charge wire up to a panel-mounted Ammeter and back.
This is going into the left field weeds as usual.
(1) Not talking about the "B" to Batt cable, that cable is the 4 awg (CTY OEM size) battery cable.
(2) We are discussing a fuse on the power supply to the panel, NOT on the AO wire (which is to the "B" post anyway, NOT back to the batty.) Read up on your harness at my link and (if OEM) its fire hazard and you'd understand the problem and what we're talking about.
(3) 4 awg is way undersized for the battery cable (but CTY saved $$) but that's a different discussion -- should be sized for no more than 3% and closer to 1% V loss to the starter.
(4) He doesn't have and we're not discussing an ammeter in the cockpit panel (leftfield.)
OK, if it's the tap for the panel, agreed; but most of these setups work much better with a glow plug relay, in which case the current in that wire is pretty small.
I don't have that harness.
Are you referring to the alternator to starter cable, or the battery to starter cable?
I was talking about the alternator B+ to the battery, not the starter. I know on some Catalinas they just jumped this wire, using the starer terminal as a junction point; but the wire form the alternator to the starter is going to have zero current flowing until the engine is - started - it's the battery to starter wire that matters here, and at typical starter motor currents, under load, you'd need something like 00 welding cable to stay inside of a 3% drop. At less than 20' round trip 4AWG works, of course #2 is better, and so on. If you're saying that you want to maintain a 3% drop on a jumper from the B+ to starter (which is where the battery is connected), for battery charging current: how long is the jumper? If on the order of a foot, 4AWG will likely suffice. For the starter to battery cable, again, at a max charging current of 50A, and a round trip distance of 20', 4AWG will give you a 3% drop.
He said he was going to reinstall the Ammeter, I thought he meant at the panel.
I’m not sure 10ga is big enough to carry 50A without substantial voltage drop and wire heating.
You probably want 100A fuse and Wire big enough to give less than 2% drop and rated for engine compartment. I use Blue Sea app for calculating wire size. My guess is at least 2-4ga but depends on distance
If the fuse ever blows while the alternator is running you WILL blow the diodes.
You probably want 100A fuse and Wire big enough to give less than 2% drop and rated for engine compartment. I use Blue Sea app for calculating wire size. My guess is at least 2-4ga but depends on distance
If the fuse ever blows while the alternator is running you WILL blow the diodes.
I was confused, too.
BTW, you can fit a Zap-stop to the alternator to protect the alternator's diodes.
Many people, myself included, have had great success with glow plug solenoids. Many engines include them as standard equipment, including Westerbeke. Many Catalina owners install them, and engines start quicker and more reliably. I had one on my C36 for probably 15 years, and wasn't buring out glow plugs. I gave the spares to the new owner.
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