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Hot Alternator

J

John Provost

New member
Hi Guys! New to the forum and I have a question right off. The alternator is getting hot (300 degrees) on my 2004 Honda 135 with 550 hours. It's charging 14 volts and the batteries are 12.6 with motor off. Nobody has touched the belt so I suspect the bearings. Does anybody know of an alternator rebuilder in St. Augustine/Daytona area of Florida. Time is of the essence.


TIA,
John
 
while charging alternator get heating up, But 300 degree is it F' or C' ?? And it got cooling fan inbuilt so it should cool down.If it is giving 14 V it is correct, may be the batteries are weak.


wajira
 
I would not assume immediately that anything is wrong with the alternator. They will heat up dramatically when continuously loaded. I would hate to find out you went to all the trouble and expense of replacing or rebuilding yours only to find that it still heats up like that.

Charging at 14 volts sounds normal but what creates heat...other than mechanical problems as you've stated.... is the AMPERAGE that the alternator is "flowing". Boats typically have very low amperage demands with the initial cranking of the engine usually the largest. And that is only a short burst. Other than that, unless you are running ALL the lights and several devices like sonar, radar,radios and pumps there should be very little amperage demand on the alternator.

Before I took it off and had it tested, I would first want to put an AMP METER on the system to see what is happening in my electrical system. If you start up and have all loads on the boat OFF, the amperage should be initially high as the alternator replenishes the amps to the battery that were depleted by cranking but should immediately go down as the battery gets "topped off" and the only load is what is required to energize the ignition system,engine computer and, perhaps, dash gauges. Somewhere well below 20 amps say.

If you were to find that the alternator is constantly being asked to produce 70 or 80 amps with all loads off then there is likely a problem with your system that you should investigate.

An old set of batteries will put undue stress on an alternator and kill it if they have high INTERNAL RESISTANCE. Other power thieves are poor connections. If the battery cables have corrosion or if the connections are loose or dirty...same thing.

The bad connections act...in an electrical sense...just like LOADS and will DEMAND power output from the alternator. All this "fluctuation" can and will occur but will not be seen on a voltmeter. The alternator can be working itself to death delivering amps while the voltmeter may not move off of 14 volts.

Amp testing is easy to do if you have an AMP CLAMP that you can put around a battery cable. It is also a great device for setting a baseline for electrical loads on your boat. It can let you know if you are adding too many "toys" to your vessel that might require that a higher output alternator be installed to keep up.

Just sayin'

Good luck.
 
jgmo said:
I would not assume immediately that anything is wrong with the alternator. They will heat up dramatically when continuously loaded. I would hate to find out you went to all the trouble and expense of replacing or rebuilding yours only to find that it still heats up like that.

Charging at 14 volts sounds normal but what creates heat...other than mechanical problems as you've stated.... is the AMPERAGE that the alternator is "flowing". Boats typically have very low amperage demands with the initial cranking of the engine usually the largest. And that is only a short burst. Other than that, unless you are running ALL the lights and several devices like sonar, radar,radios and pumps there should be very little amperage demand on the alternator.

Before I took it off and had it tested, I would first want to put an AMP METER on the system to see what is happening in my electrical system. If you start up and have all loads on the boat OFF, the amperage should be initially high as the alternator replenishes the amps to the battery that were depleted by cranking but should immediately go down as the battery gets "topped off" and the only load is what is required to energize the ignition system,engine computer and, perhaps, dash gauges. Somewhere well below 20 amps say.

If you were to find that the alternator is constantly being asked to produce 70 or 80 amps with all loads off then there is likely a problem with your system that you should investigate.

An old set of batteries will put undue stress on an alternator and kill it if they have high INTERNAL RESISTANCE. Other power thieves are poor connections. If the battery cables have corrosion or if the connections are loose or dirty...same thing.

The bad connections act...in an electrical sense...just like LOADS and will DEMAND power output from the alternator. All this "fluctuation" can and will occur but will not be seen on a voltmeter. The alternator can be working itself to death delivering amps while the voltmeter may not move off of 14 volts.

Amp testing is easy to do if you have an AMP CLAMP that you can put around a battery cable. It is also a great device for setting a baseline for electrical loads on your boat. It can let you know if you are adding too many "toys" to your vessel that might require that a higher output alternator be installed to keep up.

Just sayin'

Good luck.
Click to expand...

Good Advice! No toys. Batteries were pronounced healthy (although at least 5 years old but kept on a trickle) when it was serviced last year. That was when they said my alternator was running hot. I'll disconnect the trickle and see if they hold 12v. Connections good. I'll try the amp test.

Thanks
 
What many don't realize (but it sounds as if you might) is that the alternator is what actually FEEDS the electrical loads....not the battery or batteries. The battery is only there to provide power for initial starting and then to act as sort of an "electrical stabilizer" to smooth out the transitions or "spikes" as the alternator "catches up" to things being switched on and switched off.

If you suspect that wiring or a cable could be "worn out" or internally corroded and adding too much resistance, you can identify the problem by doing some VERY simple testing with your digital voltmeter called "VOLTAGE DROP TESTING". There are some really good tutorials on the web about how to go about this and they seem to explain it much better than I do.

The batteries being 5 years old does make me wonder. Although, some batteries DO last longer than that and if they were PROPERLY tested and passed...well...I guess... they may be ok. But I will say that I've been fooled by batteries many times even while using hi-tech test equipment.

I used to run a trucking repair shop and we would have a bad battery or two come in with orders of BRAND NEW, NAME BRAND (and I mean "the best") batteries every few months or so. And so, I know from experience, that a bad battery in a bank of four, wired in 12 volt parallel, is all it takes sometimes to take out an alternator.

Standing by to see what you find.

Good luck.
 
Great advice from jgmo. You want to know how hard your alternator is working to get an idea of how hot it should be. An amp clamp is the way to go here to be sure. Never run your engine with the external battery charger connected. Double check your wiring around your alternator and battery for good connections, clean and tight. Don't forget to check ALL earth wire connections as well. With engine running, Look at the voltages at different points between your alternator + and battery + relative to Battery - (ground), there should only be less than 0.1v difference between any locations. Check the voltage output directly on the alternator outputs as well, if this is significantly higher than the battery voltage then You have high resistance in your charging circuit somewhere.
 
Batteries holding good charge 3 days off trickle. All connections clean and tight. On my way to home Depot to get the elusive amp clamp. Not real good at this electrical stuff. It's taken me this long just to remember how to get back on this site LoL. I will check output at alternator after 5 minutes fast idle? Then compare with same at batteries. Thanks for walking me thru this. What's an "Earth wire" connection?

Thanks again
 
Our Brit and Aussie brothers, God bless 'em, call electrical ground "earth". Many of the English 12 volt systems for cars and motorcycles were "positive earth" IE: positive ground. Where the battery NEG.was hot and the positive terminal was connected to chassis.
 
Our Brit and Aussie brothers, God bless 'em, call electrical ground "earth". Many of the English 12 volt systems for cars and motorcycles were "positive earth" IE: positive ground. Where the battery NEG.was hot and the positive terminal was connected to chassis.
 
And technically our Brit and Aussie brothers are correct with positive ground. Ask yourself, what IS electricity? It is the flow of electrons. Electrons are negatively charged ions. What "attracts" a negative ion? A positive ion. So, technically speaking power truly does flow from the negative terminal to the positive terminal. (That's why all manuals tell you to disconnect the negative terminal on your battery whenever you're working on anything.)
Jim
(30 years aircraft mechanic + 8 years as a flight simulator technician USAF and commercial air carrier)
 
As I read this, I keep thinking that possibly the battery cables could be corroded internally. Try bypassing them with a good pair of jumper cables..
 
Great advice from skronkman and jgmo .

You say the batteries look OK. Is that just by checking the voltage after they have been off the trickle charger for a few days? Load tested?

Like skonkman I has seen plenty of batteries test good but be bad. At 5 years I would replace them. In my truck I would run them - in a boat where I can't walk away I would replace them no matter what other electrical system issues you may have if any.
 
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