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Ted Smith · 09-28-2017, 01:03 PM

Anybody got any answers to why my alternator fails this is the 3rd one I'm installing wondering what is burning them up within a 5 year period I have a 2001 Monaco Dynasty with the 350 ISC engine with a 200 amp Alternator where should I start looking it is getting expensive at $1,000+ a pop broke down now waiting for a new 260 amp to get here. Thanks for the information if you have any.

Mhcorrigan · 09-28-2017, 01:14 PM

What brand of alt is it and what is failing on it?

nothermark · 09-28-2017, 01:18 PM

If you can have it rebuilt and ask what was replaced. A lot of rebuilds just get a set of bearings and a quick check for functionality. If you have a local rebuilder do the work they can tell you what failed and what they replaced. Do that to a couple of anything and you start to get a clue where to start looking. One failure analysis is enough to take a cursory check but not really enough to get too serious as you don't know if it is part of a pattern or a fluke.

twinboat · 09-28-2017, 01:46 PM

When it's working, how many volts does the meter read.

If it is had a Diode battery isolator system, without the Duvac system working, it may be overcharging your batteries.

14.2 volts is the typical max voltage on most large frame alternators.

Most mechanics install the standard, off the shelf alternator, and they can't regulate the output voltage, because the isolator blocks the volts back to the regulator.

They don't use diode isolators any more but some were still being used in that time frame.

Google Duvac for more info.

kketterling · 09-28-2017, 02:39 PM

Are you hitting the road after dry camping before your house batteries are charged adequately? You'll definitely shorten the life of your alternator if it's having to charge the house batteries from a low state.

I killed mine when I made coffee without running the generator and then hit the road before charging the house batteries back up. This happened when I was dry camping.

Podivin · 09-28-2017, 02:45 PM

Quote:

Originally Posted by kketterling

Are you hitting the road after dry camping before your house batteries are charged adequately? You'll definitely shorten the life of your alternator if it's having to charge the house batteries from a low state.

I killed mine when I made coffee without running the generator and then hit the road before charging the house batteries back up. This happened when I was dry camping.

I'm NOT being argumentative, though this next question could be taken that way, it's really just a question.

How else would you charge the house batteries after dry camping?
Or are you suggesting to run the generator before leaving and/or while driving to assist the alternator in charging the batteries?

Steve Ownby · 09-28-2017, 03:45 PM

Yes, if you crank your generator and give it a couple of hours to get the batteries back to a high state of charge, you will save your alternator. Make sure to crank up your charger output.

Soppy · 09-28-2017, 03:51 PM

Do you idle the engine for long periods after starting ? At idle, when the batteries are low ,the alternator will have max field voltage trying to recharge the batteries. Also since the RPM is low the fan on the alternator will not be moving enough air for proper cooling. It would be nice to know what is failing in the alternator , and if its the same part all the time. Some alternators can be upgraded with better parts.

Ted Smith · 09-28-2017, 03:54 PM

Quote:

Originally Posted by kketterling

Are you hitting the road after dry camping before your house batteries are charged adequately? You'll definitely shorten the life of your alternator if it's having to charge the house batteries from a low state.

I killed mine when I made coffee without running the generator and then hit the road before charging the house batteries back up. This happened when I was dry camping.

No we left a park everything was fully charged something is not letting the alternator do it's job going to check int switch tomorrow to see if it's not letting it charge we are trying everything Thanks guys

oldguy70 · 09-28-2017, 04:06 PM

A two hundred amp alternator should be able to put out two hundred amps 24/7 as the do in a lot of applications. What is hard on the alternator is idling when it is charging full out as the alternator's fan is not cooling it very well.

twinboat · 09-28-2017, 05:19 PM

The alternator can't output full amperage at idle. It needs to be spinning much faster.

They most likely fail from corrosion on the slip rings, just like the genset alternator brushs.

twinboat · 09-28-2017, 05:22 PM

An example of alternator output and RPM curve.

rdelcamp · 09-28-2017, 05:58 PM

Quite buying new. Find a starter alternator repair shop. My !60 Amp LN
just failed. The repair was $115.
Ron D.

Podivin · 09-28-2017, 06:01 PM

Twinboat's 'corrosion' comment makes me wonder, is your coach spending a lot of time sitting near the ocean in salt air?
If so, could that make a difference?