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DUVAC alternator failed


jimc99999
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It appears my alternator has failed. I've verified I have chassis battery voltage and ground on 2 of the terminals on the rear of the alternator. On our last trip across the country the tachometer started acting up, and last time out the tach didn't work at all and there was no alternator charge voltage. It still drives fine, so apparently the Allison gets its rpm signal from a crank sensor and the dash tach must run off the alternator.

I have installed the BlueSea ML-ACR so I don't necessarily need a DUVAC alternator anymore. Is it more reasonable to get the old alternator rebuilt? Or just get a new/reman self-exciting alternator? I'm not sure if I have anywhere local to get the alternator rebuilt. I know I saw someone mention a shop that does exchanges but I can't find it now.

I haven't tried hitting it with a hammer yet. 

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Wish I could read the plate on the bottom. I guess I'll have to try to hit it with a brass brush and see if that makes it more legible. 

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I am one of the original 25 members that Bill D used to establish this group.  Most of those members who tried to tinker with their DUVAC alternator ended up on the side of the road.  That configuration came with your coach free, no extra charge, working for the many miles that were driven.  

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I worked with this guy. He’s in my home state of NC, but I bought it on Amazon. I had a question and he was completely awesome to work with. Highly recommend him.  

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Not to be a complete naysayer, but when my original alternator quit at 165,000 miles, I bought a replacement from AJ Electric.  It was supposedly a brand new exact replacement Leece Neville, it lasted 6000 miles.  Seems he builds the alternators in his shop with parts he gets from where? AJ Electric replaced the alternator under warranty, and told me I must have problem with my coach, couldn't be the alternator.  I checked my coach over and over, there were no problems nor any changes, I checked connections, even to the point of replacing batteries that still checked out fine, but were getting older.  That alternator lasted 2000 miles and quit.  I don't particularly think that is a good record.  I have since replaced the Leece Neville with a Delco 28si and could not be happier.  This alternator has been in service for about 8000+ miles and has been perfect, also the 28si is smaller and lighter and after replacing the alternator ourselves numerous times it was very welcome.  Parts are readily available.  Just my personal experience, take it or leave it.

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Wow! This has not been my experience yet but good to know. It disappointing that our experience with AJ Electric had been so different. Or, maybe in a few more miles, I may run into the same issues. Thanks for the reference to another alternator that you have had success with!  Thanks Willbo777

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You need an "antique" DUVAC alternator for one and ONLY one reason--your system uses a Solid State Isolator (SSI). That is the large, blue finned device in your charging system's Rear Run Bay (RRB) with three heavy cables running to it.  In its day, 20 years ago, the SSI was state-of-the-art.  It will INVARIABLY fail someday, as will your Lambert Charger (the one that charges your chassis (engine) batteries when you are connected to a pedestal.  Now, DUVAC is outmoded technology, and available at fewer and fewer sources.  If, instead of replacing your failing DUVAC alternator, you have it rebuilt, you MAY get many more years of service from it, assuming your SSI, your Battery Boost contactor ("Big Boy") and your Lambert Charger (Green finned) device work as they should.  But if you replace your SSI, your Battery Boost contactor, and your Lambert Charger device with a modern solution like the Blue Sea ML-ACR, BOTH your battery banks will be charged ANY time a charging voltage is present, AND your alternator can be a garden-variety type available at any auto parts store--the Delco 28si being a popular example (at a fraction of the price of a genuine Leece-Neville DUVAC alternator).  And your ML-ACR will accomplish the function of your present "Battery Boost" switch.

There simply is no good reason to continue trying to accommodate the limitations of the DUVAC system, UNLESS you are broken down in BFE with no alternatives.  In that case, INSIST THAT YOUR EXISTING ALTERNATOR BE REBUILT, instead of being replace with a "equivalent".  Just realize that your DUVAC system (or one of its components) will eventually (SURELY) fail, and you will find yourself at the mercy of well-meaning technicians who do not have a clue how to replace a 20-year old DUVAC alternator by any means other than rebuilding your EXISTING alternator or replacing it with an EXACT part number replacement.  When they tell you, "We have another alternator that will replace this one exactly at much less expense"...you are only days away from even more trouble.

IFF you have your EXISTING alternator rebuilt, and IFF it was indeed your core problem (and NOT your SSI or Lambert Charger) you will be OK.  If your alternator is replaced with an "identical replacement" and the tech does not understand how to properly connect the voltage-sensing wire from the previous DUVAC alternator, you are screwed, and will realize it as soon as you are a few hundred miles from the shop that "fixed" your problem.

I could write a long treatise of how and why to make the change to a Blue Sea ML-ACR, but there are now dozens of threads on this forum and on iRV2 about how and why to do this.  Search them.  Good luck in your upgrade!  Let us all know how your situation turns out, as there are dozens of very capable folks here to help you with your problem.

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Rik, your Transpo regulator is an adjustable regulator. Pop the white plug out of it to see the adjustment screw.  Those are the regulators I use and set my charging voltage to 14.2-14.4v at the battery while on fast idle. The L/N OE regulator is non adjustable.
 

I have a side radiator coach, and with engine off I contort myself to get to the underneath side of the alternator and make small incremental adjustments until I reach my desired voltage setting. That is I adjust, then start and check voltage. Repeat if necessary. My J1939 buss reads .1-.2v lower. So, Aladdin is off just a tad.

I know setting yours would be a task with the rear radiator. But at least you have a bit more knowledge now.

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Harry, thats awesome I did not know I could manually adjust my operating voltage, im a firm believer information is power, ya know knock on wood I have been very lucky with my charging system, in that I had my Alternator rebuilt which was working with no issues, however the reasoning was I was in the process of replacing the radiator, water pump, t-stat, belt. So I was looking at the Alternator and envisioned myself having to do that job on the side of the road somewhere... Yeah NO, so Always knowing how to make a project longer I removed it and drove it to the nearest rebuilder 70 ish miles away. Once installed it has been working as well as the day I took it off, on a side note I started looking for a Isolator, my 2003 HR Endeavor does not have one. Im sure over the years it has been modified, so what I found is that the alternator is wired directly to the engine batteries, then from there someone has installed a "MAGNUM smart battery combiner" which will allow 25 amps to cycle from high charge batteries to low charge batteries until the voltage is equalized at that point it just toggles back and forth to keep both pairs at the adjustable cut off setting. It does the same with the engine off and im charging from the inverter to keep the engine batteries topped up. After I bought my coach it took me some time to decipher the operation, So far (again, knock on wood) it has been working flawless. With this system I see a possible issue if and when the coach batteries lets say get run dead and it has to try to recharge four 6 volt batteries, at that point it would mean connecting a battery charger or to replace them if there was one with a internal issue.

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On 11/8/2021 at 10:17 AM, Chuck B 2004 Windsor said:

I am one of the original 25 members that Bill D used to establish this group.  Most of those members who tried to tinker with their DUVAC alternator ended up on the side of the road.  That configuration came with your coach free, no extra charge, working for the many miles that were driven.  

The configuration that came with my coach wasn't free, it was included in the price I paid for the coach a few years ago. It is now 25 years old. The "Big Boy" battery boost contactor never did work properly; it clunked and made a connection but couldn't pass enough current to start the generator, although regular jumper cables from the chassis to house batteries were able to accomplish that. The Lambert charger was failing, it no longer worked all the time. And when the alternator stopped working I figured it could be the isolator, or maybe the external exciter wiring had a problem, and I already had the ML-ACR so I installed it. Turns out the SSI may have still been working, or maybe it had a problem and killed the alternator. But it doesn't really matter now, and a new SSI by itself is $200+, and the ML-ACR which replaces all 3 devices was $160. The alternator itself made it 25 years and 75K miles, with 25K of those in the last 3 years. From what I've read here far younger alternators have failed, and there's plenty of discussion about problems with these electronic battery charging components so it's not like these parts haven't served their purpose with a reasonable lifetime.

And now that the ML-ACR is installed, I technically don't need the alternator, the generator and inverter/charger can sustain 75+ amps to the chassis batteries if the house batteries are charged which seems like plenty. Turning on the headlights increased the charge current by 20 amps. Considering that a 5 hour trip a couple weeks ago with a flaky 5 amps or less maybe being provided by the Lambert took 0.5V off the batteries, normal daytime operation doesn't seem to actually draw that much power.  However, adding a sustained 50A charging to the 25 year old Xantrex inverter/charger sounds like a good way to hasten its demise.

I called around and was told they don't rebuild alternators much anymore unless it's rare or expensive. A new 170A Delco 28si is around $230, and they'll swap the pulley for me, so that's not bad. I just need to get back to the coach to remove the alternator.  That should be fun, that old Leece-Neville looks like it weighs at least 40 lbs!

Thanks everyone for the suggestions!

Edited by jimc99999
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On my 03 Windsor the voltage regulator over charged,17.8V, my batteries.  Ruined both starter batteries. Only had 55K miles on alternator and brushes and bearings were good.  I ordered a new DUVAC regulator, installed it and mounted back on the engine. No problem.  Did I mention that I have a side mounted radiator.

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