Time for a new alternator?

[Bruce Sieloff]

Had an interesting experience today, hooked up the toad and while driving 100 miles the battery voltage on the Aladdin kept dropping until when we pulled into our destination park it was about 11.7. Normal charging runs 13.9 or so when running. Got out to check the site and closed the door behind me, engine running and dog inside, and couldn't get the door to open! The auto locks weren't responding and the key didn't work either. One of my new "park buddies" helped me charge up the chassis batteries with a honda generator until the locks finally responded and we were able to unblock the roadway and back into the site.  The inverter has brought the chassis batteries back to 13.4V on park power. Checking the alternator output yields 12.6V at idle and about the same (12.8V) at 1200 rpm. I would think it would increase at higher rpm, isn't normal about 14+V? The belt seems tight. I have noticed some occasional wild fluctuations in the "entertainment display" gauges on the dash as of late. We are currently in place for the next week so I need to get on this. If all the connections are clean and tight, should I be looking at a new alternator here or a new regulator?

[Keith Moffett]

Bruce
Just a couple points that might help.  Our alternator did that.  Shortly it got to where it would produce 12.2 or less max and dropped off from there.  Though the alternator was new the diodes were failing.  Turned out Leese Nevile didnt care that the alternator was badly built.  I had it remanufactured and it is still working  years later.  Moral is perhaps just getting it rebuilt is best.  $250 including labor vs $700 new plus.
Did have one other instance where the problem was the temperature sensor on the batteries causing wild fluctuation in charge rate.  Dont think that has bearing on the alternator.  Just the inverter.

[Edward Buker]

Bruce,

If the wires are clean and tight, I am with Keith, the alternator either has to be replaced or rebuilt. It should be putting out 14V. If it is the original it is 14 years old, by now the bearing grease is dry or depleted and that is an issue. If rebuilt, it would best be done with a Leece Neville parts kit that includes new bearings, new brushes, new regulator, and some smaller miscellaneous parts. If the shop has one in stock or can get one then you know the parts are right.

By now the heat sinks will be filled with dirt and diesel soot, so it is likely not getting the cooling that at times it could use. If there is a reputable shop around that has the parts you can probably have it back in a day or two.

Those that went with an alternate brand may want to chime in on their experience with another brand. I had mine rebuilt and would plan on a 10 year interval roughly, as a preventative rebuild point. Better if it can be done at a more convenient time then when failing on the road.

Later Ed

[Bruce Sieloff]

Is replacing the alternator a DIY job? I'm a little Leary about removing the serpentine belt,
I have a breaker bar to loosen the tensioner but I am not sure about how much down force is required.

[Edward Buker]

Bruce,

It is a do it yourself job. Removing the belt using the half inch drive recess in the tensioner is pretty easy. If you put your bar in it and just start to relieve tension you will get the idea. Just a good diagram of the belt path is in order.

Taking the alternator off is relatively easy. Remove 12V power and label the wires. Check to see that you can get the bolts loose, some spray may be in order. If you have it rebuilt check the bushing spacing on the alternator for bolting up. Those can be moved if you cannot get the alternator to drop into place between the mounts, so the bolt can go through.

Later Ed

[Joel Ashley]

It's been a lot of years, but I removed and rebuilt an alternator on the 350 Chev Mercruiser on my old boat.  Access was a lot tougher than the coach alternator would be, so that shouldn't be the hard part.  Once on the workbench. you may find online a rebuild guide much as I found in print for my Delco.  The guidance was efficient and it wasn't long before the unit was nearly like new, reinstalled, and I was back in business with the pride and confidence of knowing it was done right by my own hand.

If nothing else, you can readily remove the unit and take it to a reputable shop for rebuilding.  I got an inexpensive belt tensioning device (similar to a Gates 91107) to aid in resetting the serpentine belt, a procedure which is critical during reinstall;  just look up the belt tension parameters for your engine, or at least check the tension numbers with the device prior to removal. I'm not certain that particular device is appropriate for the belt in your question, so research that beforehand.

Then mind Ed's advice.

Joel

[Bruce Sieloff]

Got 'er done, had the alternator rebuilt at Starr Rebuild in Fresno where they determined that a diode was burned out and the rectifier needed replacing. New bearings, bushings and a bench test was $178 out the door 24 hours later. Happy there. Probably fried the rectifier during one of my house battery adventures when we didn't bring the bank to full charge. A short test on my end shows the new rebuild moves the voltage from 12.5 to 13.3V with a little throttle, a full run tomorrow should have me a happy camper. Replacement was indeed a DIY job, had to buy a 1/2" drive breaker bar to release the belt tension and a couple of sockets but it wasn't as fearsome as I thought. I was careful not to move the upper support bar for the alternator which saved me a tension adjustment issue. Probably saved $500 (mobile guys wanted $180 just to show up) and now I can do it again if I have to. Reducing the mysteries one by one. 

[Mike Groves]

Bruce,

I am curious to know what your computer reads for your battery voltage while driving.  After having a show rebuild mine about the highest I get on my Silverleaf is 13.2 Volts - seems to go from 12.8V to 13.2 which is about a volt less that spec (13.8 to 14.2).

I suspect my isolator might be bad but simply haven't thought about it too much UNTIL the generator went as I'd been supplementing the alternator by running the generator on trips.

Mike
PS we met at Pacific Shores this past summer - I am on Lot 53 and you were on Vicki's lot 20.

[Bruce Sieloff]

Mike, I remember our meeting, you were working your way through some issues at the time. It seems that no matter when, we are all "working our way through some issues" with these things. I had been reading 13.9V when the system was at full strength; I'll know how robust my rebuild is later today when we hit the road. I haven't ruled out an isolator issue where the alternator is concerned, I think it is a part of that charging system so it could be a weak point. The isolator was isolated from the inverter system when the tech who installed the inverter debugged his install to get the combiner working properly, so the isolator if it is active is would only be associated with alternator charging.

[Gerald Farris]

A battery isolator is only used on coaches that have a Duvac alternator. If your coach has a "Bird" system or combiner as some people call it, your coach does not use a battery isolator in the charging system because the alternator is only wired to the chassis battery bank and depends on the "Bird" system to combine or tie the battery banks together to recharge the house batteries from the engine alternator.

Gerald