Intermitent Alternator problem

[Alex 2740]

I am having an alternator problem and was hoping for some advice/help.

When I start the engine I will take a look at my battery monitor and notice that I am getting no juice to the batteries. After a variable amount of time (upto an hour) the monitor indicates that the alternator is finally provding a charge. This is a Yanmar 3GM and I believe the altenator is ~55 Amp and has a built in regulator. I am checking all this when the batteries are in a discharge condition allowing them to accept a charge.

I have not worked on Alternator issues to date and wanted to ask a couple of questions before digging in:

1. Do alternators ever go bad intermittently like this? I thought that they either ran or did not.

2. I'm assuming that the aternator could be fine but the regulator might be the problem. Is that possible? Likely?

3. Does these seem more like a wiring issue? I'll dig into the wiring and make sure that it's not a bad / deteriorated connction But thought I'd ask others first.

Regards,

Alex
S/V Nepenthe Savannah, GA


.

 

[Dean5735]

reverse polarity

If you have a reverse polarity switch on your panel, like my Catalina 30, you will need to switch it, so you are on alternator not shore power, I found this out just before I got a new alternator too. This protects your alternator protected from shore power.

check it out, Dean

 

[kloudie1]

Hate to be trite but Yes to all of the above.. Best to pull the altercator (any argument there?) and take it to an automotive shop to get it checked. Brushes that are very worn can do what you describe, as can a bad regulator.... but certainly check the connectors

 

[Stu Jackson]

Just to clarify

Reverse polarity has nothing to do with your alternator. RP is for 120V alternating current and the alternator is 12V D.C.

 

[alexco38]

Check the Alt indicator light

Unlike a dynamo in an outboard motor, the Alternator needs some residual megnetism in the rotor to start charging. The Alt light actually provide a very slight current (12v an a few milli-amp) from the starting switch to get the process started. If the contacts to the Alt light (on the electrical panel) is not very good, you'll get the symptom as described. Automotive electrical shop may be able to test the alternator. But when you put it back in the boat the symptom starts again.

 

[RichH]

If this alternator has a 'smart' regulator it may be nothing more that the normal time delay before the regulator 'ramps up slowly' to allow the alternator to 'slowly come on line'. Without such a ramp-up youll notice that the alternator belt will quickly wear and the alternator and other adjacent sheeves will be coated with 'belt dust' as the start-up will be 'instantaneous'. Smart regulators prevent this as they allow a slow and 'ramped-up' start of the alternator - when starting up they 'come on line' slowly. For example, some of the Balmar type regulators take 'minutes' to slowly switch on an alternator (field).
So, the important thing to monitor is what are the 'values' after the alternator is running for several 'minutes', not as you instantaneously 'start-up'.

 

[sailaway78]

The first thing

The very first thing I would do is to check the belt. A loose belt could be the source of this type of a problem. Other than that, all other advice given is correct. If the belt is tight, pull the alternator off and take it to almost any auto supply. The can check it. Then you can go for a rebuild, or get a new one. I recently upgraded mine, and a 70 amp to fit the Yanmar was under 100 bucks, brand new. If you buy a Yanmar alternator, be prepared to spend about five times as much. And they are all Hitachi alternators.

 

[RichH]

Then you can go for a rebuild

Low cost rebuilt alternators are usually slap-dash quality that may be but are usually not of good quality. If you have a 'good' alternator and want it rebuilt, take it to an automotive electrical shop (every large town has at least 2). The 'quality' and reliability of such a 'rebuild' will be vastly better than a typical bargain rebuild. Most good alternators usually can be quality rebuilt - once.

The same auto electrical shop is the place to have your 'problem' alternator evaluated/tested.

 

[Stu Jackson]

You may be interested in this topic, especially reply #10: http://c34.org/bbs/index.php/topic,5234.0.html

 

[uptownsteve]

I have the same problem

I currently have the same problem. I found that the push on connectors to the charging light in the cockpit were badly corroded. I managed to get one of the 2 connectors to the light off and sprayed it with WD40. The other one is so badly corroded that I am afraid to pull it off until I have a replacement for the light and the 2 push on connectors. I also removed the push on connector at the alternator end and sprayed it. In the meantime I am able to get sufficient voltage to excite the alternator by "goosing" the engine up to about 3000 RPM for a few seconds. As soon as I increase the RPM the charging light goes out and the alternator starts charging at 14.2 volts! Steve

 

[Dean5735]

Your alternator (I guess I should say MY) will NOT power the battery with polarity switch in the wrong position. I checked this with my marina mechanic and a v.meter. The alternator was not sending power to the batteries with the switch in the shore power mode protecting the alternator, thus, no charging when not plugged in, and after a couple days motoring and on the hook, the batteries were not charged.
On the Catalina 30 I could not get the alternator bolt out ( was gonna replace it ), I would have had to drill a hole in the fiberglass seat area to get it out with out pulling the motor. Flipped the switch and they were getting plenty of power.
Dean
ps. not trying to argue with the experts (stu) but this is what we found.

 

[Stu Jackson]

Polarity & Alternators

Your alternator (I guess I should say MY) will NOT power the battery with polarity switch in the wrong position. I checked this with my marina mechanic and a v.meter. The alternator was not sending power to the batteries with the switch in the shore power mode protecting the alternator, thus, no charging when not plugged in, and after a couple days motoring and on the hook, the batteries were not charged.
ps. not trying to argue with the experts (stu) but this is what we found.

Dean, yes, I understand, and, in spite of Ron, I am not arguing either. In this case, you have something VERY strange going on on your boat, because as we previously discussed (not argued) the polarity switch is for alternating current and the alternator is producing direct current.

Now that you've had a mechanic and/or tech to agree with you, I would be very curious to see a wiring diagram of your setup.

Here's my guess: the polarity is/was mis-wired into the alternator circuit. If you look at the C30 wiring diagrams, so kindly linked in another topic by Bob S (http://www.catalina30.com/TechLib/PartsManual/C30 Parts Manual.htm) it includes the electrical system. There is nowhere shown a connection between the alternator DC system and the reverse polarity AC. Actually there's not much there at all. If you check any other Catalina manual's electrical system diagrams, they are separate. Try ours: http://www.c34.org/manuals/1988/1988-C34-Owners.pdf Page 33 of the PDF file has the AC system.

Here's another guess: perhaps, Dean, I may be misunderstanding, but the ONLY thing on the electrical panel remotely close to anything called polarity is the "reverse polarity" indicator. Perhaps one of us is "mis-naming' or "mis-identifying" something here.

Extension of last guess: Could you be calling the 1-2-B switch the "polarity" switch? Since most boats come from the factory with the alternator output (AO) going to the C (B) post of the 1-2-B switch, my guess is that's what is happening. That's NOT unusual. I haven't heard anyone ever call the 1-2-B switch a polarity switch before. It is not a polarity switch, it simply chooses the battery bank for use (and for charging if so wired).

Last guess: your PO rewired something and used a switch on the panel for something pretty odd. Many people don't understand reverse polarity and it wouldn't be unusual for someone to disengage it and use the switch.

We do not have a switch on our panel for RP, there are three lights (the switch above is the AC main breaker). The newer boats may have a push to test button or momentary switch.

Dean, I'd love to learn more about what it is you have and hope to clear up this unusual condition. Perhaps a picture of your panel showing the "polarity" switch you mention would be a good start.

 

[Ron20324]

I'm with Stu on this one. Something is wired or labeled wrong, and shouldn't work in the way you describe. I was in the bowels of a C30 yesterday doing work for a friend (since I'm retired). Ye gads, how the plumbing has been bastardized over the years . Your electric may have had the same mechanic?

 

[Stu Jackson]

Oh, Dean

Any answer to this polarity switch thing?