Alternator Fire!! Please Help!!

[Rody1285]

Re: Electrical Issue

I have a 1996 Bay liner with a 3.0 LX Mercruiser Engine I/O.

Background:

Last summer I replaced the original alternator because it looked old and crusty and there was an issue with charging.

I ended up changing out the alternator with a new one from West Marine made by Seirra. This alternator was okay for the first couple of weeks. I decided to add another battery and the blue sea systems relay for the dual battery charging. I converted my 1 group 24 deep cycle battery to 2 larger batteries, I believe it’s the 27F series size and also added some electronic components ( stereo, amp , subwoofers, depth finder, PA system, horn, and interior glow lighting) all components were wired at a 12 V distribution block with marine grade wire. I also used a blue sea system grounding terminal.

After a couple of weeks since I installed the new alternator last year I was charging at 15.2-15.5 volts to both batteries, I disconnected the blue sea system relay to see if it made a difference and it did not. I used only 1 battery and there was no change. I also disconnected the amp and the stereo and kept all the electronics off and there was no difference. I returned the Sierra alternator 1 month later for an exchange noting the reason for return was a faulty voltage regulator (55amp alternator). This new one had similar characteristics, I would intermittently charge high about 15.2-15.5, sometimes as high as 15.8 (also I want to note that the batteries are new Ever start Marine Deep Cycle from Wal-Mart group 27) I cleaned all the terminals and connection from the main +12v wire on the starter to the battery and the large (-) ground from the engine bock to the negative post on my grounding bar. I ended up running the boat with a high charge all season last year with no issues ( about 15.2-15.4) sometimes the charge would come down to 14.8v (normal range) sometimes as high as 15.8v

This season I prepared the boat for the water and the first time I took it out the alternator caught on fire after about 10-15 min of running the boat. The alternator wire that produces the charge ( + orange wire over heated and melted the rubber cover causing the rubber to catch fire and melting the back of the alternator (see image).. I literally had to use the fire extinguisher to put out the fire because it would not smother with a towel.

Ok, I purchased a new OEM Mercruiser alternator and installed it. I still have the F***ing over charge at 15.4-15.5. I double checked all my wires for the new add on components I installed and everything is good, I even purchased larger gauge wire for the stereo and amp incase that was the problem. I even fused every single +12 wire leaving the + distribution block. I also gave every component its own ground from incase the shared ground was the issues. No Resolution!

I called a boat repair place and he told me the ground at the alternator could be bad, I gave the alternator a direct ground to my grounding block with no resolution! I replaced the burnt orange wire with a new heavy gauge marine +12 wire with no improvement. I am worried that the alternator will catch fire again with the over charge at 15.4-15.5 its been as high as 15.8 …. The starter terminal looks a little rusty where the large +12v to battery, alternator charging wire and the +12v to the boat wires meet… (Could that be the problem??) I already replaced the started twice due it getting submerged ( I forgot to remove the drain plug and it rained over night and by time I checked out the boat the bilge was full of water to the level of the starter)

So I am at complete loss at this point, so much so that I spent the time to type this entire effin post. What can I do to track the source of the over charge?

What could be causing the over charge?? Battery size? 2 batteries? ( blue sea said no when I called them)

The batteries are only 6 months and 9 months old and have been on a float charger over the winter, could it be the water level in battery?? (that is on my list to check)

Can I disconnect the orange wire and connect my millimeter at that terminal while the alternator is on to see what the output of the alternator is without it being connected to the rest of the boat??

Btw, I have a digital meter on the boat that is connected to each battery and the digital multi meter also corresponds with the charge readout so my reading are accurate.

Could old corroded wiring be causing this? If so where would I start?

Could it be the sense wire from the alternator, the small red and purple wire?

Is there an adjustment on the alternator that I don’t see to lower the charge output??

I plan to make a video detailing this issue and I will post that within 1 week or so.

If anyone has any info or suggestions to help me figure this out I would greatly appreciate it.

 

[GA_Boater]

The starter terminal looks a little rusty where the large +12v to battery, alternator charging wire and the +12v to the boat wires meet… (Could that be the problem??)

Instead of looking at it, clean it with a wire brush, including the wire lugs. And pop the battery caps and check the water level because overcharging can cause it to boil off.


When the alternator went sparky, was all the added electrical stuff on? Maybe you're asking too much out of a 55A alternator?

 

[alldodge]

Check this with motor OFF. Red/Purple should have 12V full time, and Purple should have 12V only when key is ON

 

[Rody1285]

Instead of looking at it, clean it with a wire brush, including the wire lugs. And pop the battery caps and check the water level because overcharging can cause it to boil off.


When the alternator went sparky, was all the added electrical stuff on? Maybe you're asking too much out of a 55A alternator?

1. When the alternator went "sparky" the components were on (pioneer stereo, sub-woofer, amp and Hook 5 depth finder), but there over charging was present prior to that.
2. I will be checking the water level when I get back from vacation next week and update you. I will also make a video documentary to help others who may have this problem.

 

[Rody1285]

Check this with motor OFF. Red/Purple should have 12V full time, and Purple should have 12V only when key is ON

I will be checking this next week, and let you know what my readings are.

Thanks,

 

[H20Rat]

Going to ask the obvious question, I don't think you covered it, but what is your resting battery voltage? I've seen plenty of cheap meters that were really bad at simple things, like voltage.

 

[Alan Lloys]

Sounds to me like a wiring issue on the "S" wire.
The S terminal is the sensing wire to regulate the voltage. This needs to be connected to the battery that is always charging.
My guess is that you are missing this wire connection. Maybe you missed it when installing the battery switch.

If the S terminal does not have voltage the alternator will give max voltage and eventually overheat.
If there is not much voltage drop in the wiring you can jumper the S terminal to the + terminal. This will regulate the voltage based on the alternator output but will not adjust for wiring voltage drop. Many smaller boats have this jumpered and some alternators has the jumper pre-wired.

 

[poconojoe]

Interesting thread. I'd like to follow. And I hope the OP resolves the problem soon.

 

[Rody1285]

Check this with motor OFF. Red/Purple should have 12V full time, and Purple should have 12V only when key is ON

Hi, I just checked the red and purple wire... it looks like the purple wire is 12.5 volts when the key is in the on position. The red wire is 1 - 2 volts with the key on or off pretty much no voltage... could this be root of all the overcharging problems??? If so, where does that wire lead. I checked all the fluids in the batteries and everything looks full, the plates are covered.

- that red wire is the sense wire? Can I bypass this and wire to battery.

- is there an easier way to figure out the source or I need to trace the wire back and repair source of corrosion?

Where is the s wire?

 

[alldodge]

could this be root of all the overcharging problems???

Yes, this is your issue.
Run a wire from the 50 amp breaker to that lead. There are at least 2 wires on the breaker, but one is solid Red and the other is Red/Purple. You need to come off the Red/Purple side to the ALT

 

[Rody1285]

Solved!!!!!

Finally after months of frustration the problem is solved. It turns out that the red wire with a purple line that connects to the back of the alternator had corroded and broken off where it attached. I followed the wires back behind the engine ( I had to unwrap the electrical tape ) to a point where 4 positive +12 volt wires attached together, the connector was a piece of crap that was made out of bare metal. This had corroded and the wire to the alternator that was suppose read ( +12v full time was corroded and broken off at that point) I replaced the wire and used a house hold wire cap to test it. Sure enough that was the issue. Once I tested the boat I was charging at a cool 14.3 and 14.4, no more (15.3 - 15.8v)

Thank you for the replies, hopefully this helps someone else someday. I am headed to the store today to pick up a new 4 way marine grade butt connector with heat shrink to finalize my repair. I attached some images. I also plan to pick up a new fire extinguisher as mine was used up when the other alt. caught fire.