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Donzi Vol
07-01-2010, 10:53 PM
I've been having on and off issues with my alternator for a while now. Basically the motor runs great, mostly due to a lot more than a tune-up since I got it last August. The only recurring problem I'm having is the electrical system not charging properly.

The original alternator wasn't doing the trick, so we replaced it. When we hooked it up (self-exciting, one wire alternator wired directly to the battery) it began charging. Then at the end of last season, it stopped charging because the battery ran down so far that the key wouldn't even engage the starter after a short cruise.

We revisited the issue this season, and I took the alternator to get tested. Sure enough, it wasn't charging, so they replaced it. I hooked this one up by keeping the wire to the battery plus a pigtail wire to the starter silenoid. Now it seems to either be charging sometimes, or only a little. This seems to be the situation because I ran out 25 gallons of gasoline on a new battery two weeks ago and never lost any power. Then this past weekend, the same new battery was cranking just fine, but died on me in the middle of cruising. All of this after about 25-30 miles of on and off cruising...all the while the motor running great. Thankfully I had my always handy second battery.

So...what are your thoughts? I suppose I'll get the new (now 3rd) alternator tested this weekend.

Thanks as always,
David

Tidbart
07-02-2010, 08:52 AM
Easy enough to check if it charging. You need a voltmeter and use a fully charged battery. check the voltage across the terminals. Should be about 12.6 volts., 2.1 volts per cell. Now start the engine and bring it above idle, say 1000 rpms. Check the voltage on the battery while running. Should be,13.7-14.7 volt. If I remember correctly, marine systems give a little higher voltage than autos, 14.2 max was my rule of thumb on cars.
If you are out of the range, low=bad alternator, high=bad regulator. Either way, you have to change the alternator.

I would do this before yanking it out. It is an easy test. Also, make sure your wiring is good, not rubbing or chafed somewhere.

B

mattyboy
07-02-2010, 09:31 AM
two batteries?? battery switch????

old boat, does it have an amp meter?? original alt have an external voltage regulator or an internal one??? what about the new one???

DonziJon
07-02-2010, 10:34 AM
A V8, ..I use this as an example of an engine that needs to fire Eight spark plugs, will run for HOURS on the battery alone....even while the alternator is doing nothing..ie; not charging. :bonk:

Cuda
07-02-2010, 10:38 AM
A V8, ..I use this as an example of an engine that needs to fire Eight spark plugs, will run for HOURS on the battery alone....even while the alternator is doing nothing..ie; not charging. :bonk:

If I remember correctly, a car will run on just over 8 volts.

Tidbart
07-02-2010, 11:06 AM
If you are out of the range, low=bad alternator, high=bad regulator. Either way, you have to change the alternator.

Let me clarify a little more. That statement was assuming an internal regulator. Obviously, you wouldn't change the alternator if the external regulator was bad.

B

mattyboy
07-02-2010, 11:22 AM
Let me clarify a little more. That statement was assuming an internal regulator. Obviously, you wouldn't change the alternator if the external regulator was bad.

B


yes very true,


the reason i ask is my old 351w ford had an external regulator on the old alt. when i replaced with a new one I was told i had to remove the external one ( the new one had an internal one)which i did. I also had to cut a wire out that had to do with the amp meter/ tach which backfeed the coil if i remember correctly( it was needed on the old setup but not the new one). the motor would run fine but would not shut off with the key once started.

not sure how long a v8 will run on just the battery but i do know a v8 will idle for about 10 minutes after it's fuel has been shut off ;) and also a 4 cyl ford focus on a brand new battery will run from new haven conn. to just shy of the tappan zee bridge at night with the lights on

I guess my point is if your old ford is setup like that, changing the alt. might need some other mods to make it work correctly.

DonziJon
07-02-2010, 11:50 AM
Something to ponder. A friend of mine had a '79 Ferrari 308 GTS. It had carburetters Vs Electronic Fuel Injection. The alternator was kapoot and would NOT charge the battery or do anything else. It's location in front of, and down under the engine made it almost imposable to remove. So it had to be done by a professional with the proper tools..most importantly a LIFT, which he did not have.

Cash was not readily available at the time, for various reasons. This did NOT mean the car could not be driven. It was just an occasional Sunday Driver anyhow.

He would routinely take the car out for an entire Sunday ride...with NO functioning Alternator. ONLY the battery was there for electricity for Ignition and anything else. You could start the engine any number of times, and then Drive It ALL DAY On The Battery Alone....say 150-200 miles..Rhode Island down to Connecticut and back. The only catch was don't use the headlights or radio. No one with a Ferrari uses the radio anyway.

If the car had had Electronic Fuel Injection requireing electrical power, it might have been a different story. :bonk:

Dr. David Fleming
07-02-2010, 01:11 PM
When the alternator was first equipped on the American automobile - Chrysler say 1963 they had a TV commercial where they took the battery out of the car and drove it to Florida on the alternator power only.

In that day there was an external electro-mechanical alternator regulator that sensed voltage drop in the system and then cut in the field circuit on the alternator - 36 and 46 amps was the max power for most alternators.

If you wanted to test the alternator you could simply jump the field terminal on the back of the alternator to the power terminal and it would run full power - usually observed on the car dash instruments as a amp meter reading pegged at C for charge. If the jump didn't work the amp meter would stay on D side for Discharge.

Eventually they went to a solid state regulator and finally incorporated this this into the back of the Alternator where it is today on most Mercruiser.

Now a lot changed when computerized and solid state components were included in the engine package - one was the requirement for a constant voltage supply to stabilize the electrical system to keep the fuel injection, ignition and other components alive. The battery became both a filter and a constant supply of 12 volt electricity. If you remove the battery, hook the battery up backwards, short out the system, or do other things like turning off an unprotected battery switch all bets are off as to what voltage spikes, or other damage can be done. Early solid state systems were very sensitive to this. Now it seems they are more idiot proof - except for unexpected issues, take Toyota and the runaway car example.

Another thing, in the day most car dealers rebuilt everything, starter, alternators, power stearing pumps, water pumps everything. Then the local machine shop did this, then they started selling rebuilt equipment and aftermarket, and now it is foreign and a lot of it is junk.

It got to be so bad that remanufactured alternators would not produce current at low rpm and they would not produce the rated power. We used to use a smaller drive pulley to get the performance but they would not carry the load of lights and motors. Many remanufactured alternators were crap. Today I always keep my OEM and have the local to Detroit Suburban electric fix it. I think the quality of the copper wire and the number of windings was reduced in the foreign stuff.

Wiring you alternator in your boat should be a fairly simple job if you know your electrical. It has to be grounded and it has to connect to the battery and if an external regulator this has to work and have good wiring connections. Your test instruments are a continuity light, volt meter, amp meter and ohm meter - brother that's all there is unless you get into computer scan tools.

Hope this helps

Moody Blu'
07-02-2010, 01:53 PM
Why do you have a pig tail to the starter solenoid? if its a one wire ALT run to the battery thats all you need.
sounds like you may have a battery that is too small, running too much electronics and it keeps killing the alternator. or you have a electronic that is draining constantly
what is your current batteries specs?
Battery group size
*
Cold cranking amps (CCA)
*
Reserve capacity (RC) for your vehicle

Donzi Vol
07-03-2010, 01:17 AM
Thanks for the thoughts and input, guys. A few answers to the questions, and then my next step...


Easy enough to check if it charging. You need a voltmeter and use a fully charged battery. check the voltage across the terminals. Should be about 12.6 volts., 2.1 volts per cell. Now start the engine and bring it above idle, say 1000 rpms. Check the voltage on the battery while running. Should be,13.7-14.7 volt. If I remember correctly, marine systems give a little higher voltage than autos, 14.2 max was my rule of thumb on cars.
If you are out of the range, low=bad alternator, high=bad regulator. Either way, you have to change the alternator.

I would do this before yanking it out. It is an easy test. Also, make sure your wiring is good, not rubbing or chafed somewhere.

B

I've actually done the volts check on the new alternator, and it was low. It would increase as the motor rev-ed up, but only to about 12.5V. It wouldn't get up to 13.4. However, I thought it might just be that it didn't have a chance to get "excited" so I went to the water, and all seemed better than fine. Hence, my confusion.


two batteries?? battery switch????

old boat, does it have an amp meter?? original alt have an external voltage regulator or an internal one??? what about the new one???

As far as two batteries goes, I have yet to mount the batteries and install the switch. Haven't found the time or decided on the placement yet to do the project. However, I've learned over the years that it's a good idea to have an extra battery in the back-up arsenal in the boat...good alternator or not.

I'm almost certain that the voltage regulator is internal in the alternator. If external, what would it look like and where would it be located on my 351? Amp meter on the dash, but I don't feel that it's incredibly reliable.


yes very true,


the reason i ask is my old 351w ford had an external regulator on the old alt. when i replaced with a new one I was told i had to remove the external one ( the new one had an internal one)which i did. I also had to cut a wire out that had to do with the amp meter/ tach which backfeed the coil if i remember correctly( it was needed on the old setup but not the new one). the motor would run fine but would not shut off with the key once started.


I wired it that way on accident when I was placing the alternator the last time. Really freaked me out when I couldn't turn it off!


Why do you have a pig tail to the starter solenoid? if its a one wire ALT run to the battery thats all you need.
sounds like you may have a battery that is too small, running too much electronics and it keeps killing the alternator. or you have a electronic that is draining constantly
what is your current batteries specs?
Battery group size
*
Cold cranking amps (CCA)
*
Reserve capacity (RC) for your vehicle

This is probably where I've left out some important details. As I've said before, it is a supposedly one-wire alternator. It is a stock GM alternator that I suppose was added sometime in the past. Since I couldn't get it to work by a simple single wire to the battery, I decided to go the extra mile. It has two prongs for the internal voltage regulator where you can plug in a "pigtail" and thus have a signal sent to the "sensor" prong to start the alternator. I then wired it to the silenoid so that it would begin charging as soon as the ignition was on. Apparently this didn't do the trick, though.

I did some online research and found this:

http://mightymo.org/Proj_OneWire.html
I'm pretty sure that the last few slides are the important ones in my situation. I'm going to do the "jumper wire" method tomorrow and we'll see what happens.

BUIZILLA
07-03-2010, 08:12 AM
couldn't hurt to add a ground wire to the case...

mattyboy
07-03-2010, 09:34 AM
my external regulator was mounted on the rear part of the intake manifold on a small bracket

Donzi Vol
07-03-2010, 09:39 AM
couldn't hurt to add a ground wire to the case...

I was actually curious about the ground. Right now it has a ground wire running from one of the bolts on the case to the engine block. That should do the trick, right?


my external regulator was mounted on the rear part of the intake manifold on a small bracket

Cool, I'll give it a look today. Thanks

Cuda
07-03-2010, 09:53 AM
I was actually curious about the ground. Right now it has a ground wire running from one of the bolts on the case to the engine block. That should do the trick, right?



Cool, I'll give it a look today. Thanks
A bad main ground is a common problem in boats. It's not like me manufacturor is nice enough to put it somewhere you can reach. They all seem to be located on the bottom of the engine. A ground wire doesn't care where it's attached to the engine as long as it's constantly hooked to the engine/

Donzi Vol
07-03-2010, 10:40 PM
So here's an interesting story for you (here is where my pride is hurt a little). Last week when all this came to a head, I just put the boat on the trailer and then in the garage. I didn't take a look under the hatch until today. A picture is attached of what I saw coming from the alternator. I thought, "hmm...that wire isn't connected to anything". One of my crimps/splices/whatever you want to call them came loose on the wire going from the pigtail to the starter silenoid. I repaired the connection, assumed all was well and headed to the water. The boat ran fine, but even after a 5 minute ride at 4000 rpm plus, the volts meter was reading 12.48 consistently. I stopped twice to check (with motor running, of course), and the same result both times. I'm going to try the "jump wire" from the pigtail to the single post on the alternator to see if that makes any difference. If not, then I guess it's back to getting it tested. Ugh...

Btw, I've also attached a picture of the motor for anyone who would like to take a look. That seems to be a common trend around these parts.