alternator problem

[Keith Moffett]

Hi all
I sure would appreciate suggestions as we are some distance from home and not near a metro area for service.  

When we started this trip the Dash guage and the Silverleaf both indicated that we were getting 13.8 volts or so pretty steady.  Two hours later we are at the coast and it is reading 12.1 to 12.7 volts.  half hour later it is varied from 11.9 to 12.4 volts and tending to stay longer on 11.9 as time passes.
This is a Leece Neville alternator (160 amp / 14V) about three years old and only 3K miles on it or so.

When we arrived at the RV park I checked the batteries and they were getting about 12.5 volts.  I read output on the alternator which was also 12.5V.

If this gets worse it wont even reach 12 V.  The alternator seems fine as are the connections on the alternator and batteries (4 years old).  The serpentine belt seemed fine with no wobble as it turned.

Does this sound like diodes or regulator and what do you think of my chances of making it 3 hours to civilization?

Thanks
Keith

[Roy Mueller]

Keith  Run your generator Hold your boost button down or put a jumper on the boost selenoid     make sure you have the inverter /charger on

have alternator tested   Roy MUELLER

[Edward Buker]

Kieth, basically Roy is providing the means to use the generator and inverter to provide a constant 13.8V to the chassis battery bank. The 12 jumper is to keep the solenoid switch between the banks on, given the dash switch is momentary. With a meter and someone pressing the momentary switch you will find 12V being applied to one of the small terminals. Find a constant 12V source point and make the jumper.

You could also stop in an automotive store and buy a battery cable with lug ends of suitable length to tie together the +12V terminal of the chassis and house battery banks. Basically leave that jumper in place until the alternator is fixed.

Later Ed

[Keith Moffett]

Thanks Roy and Ed, this is a much simpler plan than mine and will help alot.
Keith

[Joel Ashley]

Holding the boost switch down is an option, but not the best among the choices, Keith.  It is meant to provide enough amperage to start the engine if the chassis batteries can't do it alone.  You release the switch after starting - as Ed points out it is a momentary style of switch.  

But holding it down for long periods, counter to its engineering, will overheat the solenoid through which it functions, and the solenoid will likely fail when you need it for a start some day.  Been there, done that.  I once used mine to keep the headlights on so we could make it to a destination after dark.  It worked, but it also smoked the Ford-type transfer solenoid.

I afterwards built and carried a foot long #10 battery cable with large alligator clamps at either end, just in case, to jump the coach and chassis batteries direct, similar to what Ed proffers.

Joel

[Keith Moffett]

Just an update
Thanks for all the input.  We made it safely home using the above methods.  Having started the day with fully charged batteries via our battery charger, the inverter / charger was enough to put 13 volts or so into the chassis batteries as we traveled.  We didnt need headlights and the rain held off so no need for wipers.  Still though the batteries were 12.9 volts at the end so we were loosing some ground.

I have learned alot from this forum but this situation would have been much worse had it not been for you folks.
Thanks much
Keith

[Joel Ashley]

Glad you made it home okay.  Be sure and let us know exactly what was haywire, Keith.  That newer alternator shouldn't have gone bad already.

Joel

[Keith Moffett]

UPDATE - 2

OK, here is the backround;
Leece Nevile alternator was replaced with brand new in 2009.  Since there has been about 3500 miles.
The original alternator had some wire connections that were burned at the time of replacement but no signs of damage other than normal failure.  

Today;
The original alternator was pulled apart at the shop and was found to have a bad regulator and the wires leading to it had been cut short and re soldiered to be lengthened.  This had created a short.  Most of the six diodes were bad and there was a small bit of corrosion on a winding that didnt test bad.

The 2009 (leece Nevile) replacement alternator was also pulled apart.  This was the new one in 2009.  This one had started to fail Sunday and was still putting out 12 volts or so.  
The regulator tested good but the windings were completely burned in a couple places.  One of the diode connecting wires was completely fried and bare along its full length.  All of the diodes are shot.  This unit was so bad that the bench testing motor that spins the alternator groaned trying to turn this unit and the bearings were still good.  
I forgot to mention that from the outside there were no signs of damage.  All the wire connections were solid and in good shape.

This alternator was working and solid at 13.8 volts about 1 minute after engine start up until Sunday AM.  The only recent changes to any wiring in the MH was the (Sprague - Meuller) headlight modification.  I dont see how that could be involved.

THE QUESTION:

What the heck could have caused this alternator to melt down without signes of damage elseware?  What should I check or look for?  

I need suggestions on this as the shop doing the rebuild is good on alternators but not so much on Coaches and the differences in wiring etc.  Sure would hate to blow a new alternator, again!

Thanks Much
Keith

[Joel Ashley]

Keith-

Alternators on motor homes are subject to overwork if owners dry camp for even a day, and then drive off without using the generator to charge the batteries back up.  Other threads on this Forum may have already clued you in on that.  To my notion, that circumstance is probably the most common cause of the failure of a perfectly good alternator, and the overheated windings and other components in your unit are telltale of such a situation.  That is not to totally rule out another cause, such as a short circuit to ground somewhere, but the evidence is obviously indicative of too much current ouput for too long.

You alone know what your habits have been regarding dry camping and batteries.

Joel

[Edward Buker]

Besides the heavy load issue Joel mentioned, the batteries themselves can be an issue. If you have one battery with a bad cell it will continue to call for heavy current and can destroy an alternator. You should check the tightness of the connections and look for any copper corrosion at the alternator, at the isolator if you have one, the heavy duty fuses in the battery bay, and the battery connections. If all of the larger wiring is clean of corrosion and secure then beyond that point things are well fused at lower current levels. A loose connection, ground or otherwise can allow the alternator output to float up voltage wise which can then take out a diode.

So the bottom line is if the batteries are all good, and the conenctions are all good, no fuse or breaker has given you any evidence of tripping then just chaulk the fail up to some component in the alternator giving up the ghost (most likely a diode or regulator) and taking out the rest of it. The alternator was three years old, not  a long life, but the diesel pusher configuration is hard on alternators given they are air cooled and the air stream is hot to begin being mounted aft of the exhaust manifolds. Also, my sense of it, is that the air flow used to cool the alternator is also being pushed against the normal air flow through the engine compartment. Probably the best thing you can do to extend the life of the alternator is to manage the current demand to keep it on the low side, especially when it is hot out or you expect excessive engine heating like climbing a pass. The alternator was really designed to fit in the fan wash on the front of an engine with plenty of air flow.

We should not be too surprised when an alternator goes to its final resting place given it was not really designed for this configuration....

Later Ed  

[Dick Simonis]

For what's it worth, I would sure look at a Powerline Alternator to replace the stock unit if mine ever craps out.  I had one on my 50' sailboat that lived in horrible conditions tucked away in the bowels of the boat, surrounded by salt laden air, no ventilation, ran at full output to recharge the 1300 AH battery bank and never ever had a problem.  On our MH's the alternator lives in a nice well ventilated compartment, relatively clean with lot's of airflow and small battery banks.  To me, at least, failure due to working like they should boggles the mind.  Why should we need to run a gen set to charge batteries when we have a 160A alternator and only a small 4-600 AH battery bank...something seems out of wack.

[Richard And Babs Ames]

Dick did your sailboat have a sophisticated power management system that monitored the output of the alternator. I do not think most motor homes have a marine grade system which could be a part of the reason we get the high loads at start up. I am not technically up to date on marine systems, but I would like to know.

[Dick Simonis]

Dick did your sailboat have a sophisticated power management system that monitored the output of the alternator. I do not think most motor homes have a marine grade system which could be a part of the reason we get the high loads at start up. I am not technically up to date on marine systemsbut I would like to know.

Not paricularily sophisticated but I did use a 3 stage Balmar external regulator.  It's been awhile but I believe the either the regulator or the alternator may have had a thermistor to reduce output if it reached max temp.  However, Powerline Alternators are designed to run at very high temps so I might be thinking of a differant boat...had a few.

[Edward Buker]

This is a Powerline link. They seem to use heavier components and support higher temperatures. They may have a more efficient alternator fan design for diesel pusher configurations but they did not mention it. Dick has a good point here and it is well worth a check with them, especially if they have built a specific configuration for the pusher design. Anyone who does marine components certainly studies reliability and strives for providing a long life.

http://www.hdpsi.com/24HD%20Series%20Alternators/24HD%20Alternator.htm

The boat environment is terrible for corrosion but heat wise it is actually quite good. The exhaust is a wet exhaust, the engines are small displacements and they use wet heat exchangers. In addition they constantly pull cool air in from the deck vents to feed the air intake. The current demands are high but the temperature of the environment is probably quite stable compared to our pushers. They also tend to run the diesels at a constant high cruise RPM range which helps with all of this alternator fan cooling flow. Hope there is a pusher design....

Later Ed

[Wayne Tull]

I was trying to find operating range for a 160 amp alternator and the below test procedure was all I could find.

"Select proper load switch and apply load for 10 seconds. (Load should not exceed75% of total rated output rating of alternator)"

The ten second limit could be to protect the test equipment.   I haven't looked at my alternator and I have tended to follow the run generator approach but, if my alternator goes out I will be looking for an upgraded unit for output and temperature rating.

These types of of postings are great because they get me thinking about problems that I haven't experienced yet and can plan my repair action before it happens.