recurring alternator problem

[Birdseye]

Every six months or so I have to replace the regulator / diodes on my alternator. The engine is a volvo 2030 and the alternator is standard. The process starts with an alarm beep, then the tacho drops to zero, then a few seconds later it recovers. All becomes more frequent.

I suspect overheating since the alternator becomes too hot to touch but this is difficult to understand since the engine installation is standard ex manufacturer sono reason every other similar boat wouldnt have the same problem.

Ideas?

 

[sailorman]

an alternator rated @ 70 amps will be too hot to touch much like a 100 watt light bulb

 

[VicS]

Every six months or so I have to replace the regulator / diodes on my alternator.
Ideas?

Just to clarify.

Is it the regulator and brush assembly or the diode assembly or do you replace both.

Had the alternator checked by an auto-electrician?

 

[wotayottie]

Both.. And the alternator itself is OK.

 

[VicS]

an alternator rated @ 70 amps will be too hot to touch much like a 100 watt light bulb

Not a good analogy. In a light bulb virtually all the electrical energy input is converted into heat.

In an alternator most of the (mechanical) energy input is hopefully converted into electrical energy for use elsewhere onboard.

They do run hot though as they are not 100% efficient and the shortfall ends up as heat

 

[VicS]

Both.. And the alternator itself is OK.

I'd be looking for the possibility of a bad connection somewhere between alternator and battery, not overlooking the negative. Iffy isolator switch ???.

 

[peteK]

No

Every six months or so I have to replace the regulator / diodes on my alternator. The engine is a volvo 2030 and the alternator is standard. The process starts with an alarm beep, then the tacho drops to zero, then a few seconds later it recovers. All becomes more frequent.

I suspect overheating since the alternator becomes too hot to touch but this is difficult to understand since the engine installation is standard ex manufacturer sono reason every other similar boat wouldnt have the same problem.

Ideas?

I would check all connections to batteries,it may be going open circuit.

 

[Birdseye]

Bad connections was an obvious thought, maybe even a broken wire. But if that were the issue then the problem would occurr much more in rough weather with the boat being thrown about than in calm. And it doesnt.

 

[macnorton]

I would check connections/split charge relay as said and,

What batteries are you charging? (are you asking too much from the alternator)
Do you have enough ventilation? (is it failing because its overheating)

Would a larger (industrial) alternator solve your problems?

 

[JumbleDuck]

They do run hot though as they are not 100% efficient and the shortfall ends up as heat

Agreed. I'd expect around 80% efficient, so mechanical losses in heat would be about 1/4 of the electrical output. In this case that would be 12V x 70A x 1/4 = 210W, which is a fair bit, but shouldn't be anything like lightbulb hot as the alternator has a cooling fan.