Leece Neville alternator diagnosis, continued

[pybyr]

Passing along the trouble-shooting process in case it may help someone else with the Leece-Neville 165 amp alternator (used on emergency vehicle fit-ups on the F Series).

Since I'd been told by multiple sources that the regulator is one of the few things that goes bad on these alternators, I ordered one and got it today. Pulled the alternator, put in the new regulator, put the alternator back on-- still no output.

So... took off the pulley and fan, removed the three long through-bolts that hold the alternator casing together around the stator, and carefully tapped the thing apart. Removed the main rectifier packs, and tested with a multimeter on diode-check function. Negative rectifier assembly checked out OK; positive rectifier assembly was kaput on all three of the individual diodes-- _no wonder_ I was getting zero output... Rotor checked out appropriate winding resistance, and no shorts to shaft. Stator windings all had continuity, and no shorts to case.

So at least now it's clear what needs to be done to get this unit up and running. A shop about an hour away has the rectifier modules, and is open Saturday AM, so off I go in the morning.

I do have to agree with what people told me about the build quality of the Leece-Neville alternators: this thing is Hell for Stout.

I'm now remembering something I was told about a month after I bought the truck-- that the reason it had two new batteries is that one of the volunteer FD members had dropped a wrench across the battery terminals and there'd been a huge arc. I'm now guessing that the rectifier took a hit, and maybe even one or more of the diodes went out, causing the remaining ones to carry a higher load, and leading to their eventual demise.

Hopefully I'll be able to report tomorrow that the unit is charging again.

Thanks for the support 'round here.

 

[MIDNIGHT RIDER]

It is good that you decided to keep the Leece-Neville.

Like already discussed, the regulator and the rectifiers are about the only things that ever fail and failure of either of those is quite rare on applications such as our's.

They do wear out occasionally on big trucks that see over 100,000-miles per year.

 

[sassyrel]

It is good that you decided to keep the Leece-Neville.

Like already discussed, the regulator and the rectifiers are about the only things that ever fail and failure of either of those is quite rare on applications such as our's.

They do wear out occasionally on big trucks that see over 100,000-miles per year.

tell yah good one..i own a 96 passat di--120 amp alt...those last near forever..the last one--lasted 325,000.before i replaced it--and the one off of the passat v6 gas is the same--minus the 7 rib pulley---no big deal to replace--used was 35 off of a 36,000 mile engine!!! know why they last sooo long???--bosch bearings----and the slip ring dia in the alt--it almost half of american dia--which means---the brushes last near forever--

 

[MIDNIGHT RIDER]

tell yah good one..i own a 96 passat di--120 amp alt...those last near forever..the last one--lasted 325,000.before i replaced it--and the one off of the passat v6 gas is the same--minus the 7 rib pulley---no big deal to replace--used was 35 off of a 36,000 mile engine!!! know why they last sooo long???--bosch bearings----and the slip ring dia in the alt--it almost half of american dia--which means---the brushes last near forever--

What, pray tell, is a "passat" ??

 

[Compu Doc]

If you look in the previous responses to your several threads I was saying it was the rectifiers. Now you know that was correct.

I hope the shop your taking it to does not charge as much that it would have cost to replace it.

 

[pybyr]

Just came in from re-installing the alternator in the truck after replacing the rectifiers myself (got a new set of rectifiers from a local shop for about $30).

Hooray-- now I have output-- set the regulator to max 14.2 volts, measured at the battery, at 1500 RPM

I've replaced rectifiers in other alternators, but these were a royal pain-- lugs needed to be soldered onto the ends of the wires (which came pre-stripped), and the soldering is highly familiar to me, but then it turned out that the wires were a bit longer than they needed to be, so I had to do a 3-D jigsaw puzzle to get them to fit and not be at risk of getting abraded by the spinning rotor.

Total cost of parts came in at under $70 - but this was one of the more frustratingly time-intensive DIY tasks I've done in a while. Here's hoping it's done once and for all for many years/ miles. And at least I know it's not one of the low-grade remanned units that seem to flood the replacement market.

Thanks to all here who offered suggestions and support.

 

[sassyrel]

What, pray tell, is a "passat" ??

vw

 

[sassyrel]

Just came in from re-installing the alternator in the truck after replacing the rectifiers myself (got a new set of rectifiers from a local shop for about $30).

Hooray-- now I have output-- set the regulator to max 14.2 volts, measured at the battery, at 1500 RPM

I've replaced rectifiers in other alternators, but these were a royal pain-- lugs needed to be soldered onto the ends of the wires (which came pre-stripped), and the soldering is highly familiar to me, but then it turned out that the wires were a bit longer than they needed to be, so I had to do a 3-D jigsaw puzzle to get them to fit and not be at risk of getting abraded by the spinning rotor.

Total cost of parts came in at under $70 - but this was one of the more frustratingly time-intensive DIY tasks I've done in a while. Here's hoping it's done once and for all for many years/ miles. And at least I know it's not one of the low-grade remanned units that seem to flood the replacement market.

Thanks to all here who offered suggestions and support.

yah,,and you know what you have!!!

 

[pybyr]

I'm back with another puzzle about this alternator.

Worked like a charm since end of January, until a week and a half ago I noticed my volt gauge reading low during a road trip. What timing.

Made it home then wouldn't start the next day.

One of the two batteries was dead and un-chargeable, so I just bought and put in a pair of CAT batteries. Great units, thanks to everyone here for bringing them to my attention.

Now, the truck starts, but the volt gauge still reads low unless I keep the truck in neutral and REALLY wind the engine to well over 2000 RPM.

Sometimes the voltage pops up and lights hit full brightness after a single wind-out, sometimes it takes several times. Sometimes it stays up after initially popping up, sometimes it takes another couple of of wind-ups. Usually once the voltage comes up, it stays up steadily, even when the engine is let back to idle.

There is 12 VDC to the Leece-Neville's regulator "activation" terminal at all times.

For a recap on what I did in January, I replaced the regulator and both diode trios, confirmed that all windings had continuity and no shorts to ground, confirmed that the brushes were in excellent shape, and polished the slip rings.

What the _____ is going on now? I can't afford to wreck my new CAT batteries or get stranded.

Since the alternator's on-board regulator is activated by the third wire 12 VDC feed, I am at a loss as to why revving the engine causes the alternator to suddenly wake up.

Appreciate suggestions, as always

 

[MIDNIGHT RIDER]

Post your problem here :

http://news.prestolite.com/?q=forum


: in the Leece-Neville "SUPPORT" forum.

If anyone can help you, surely they can.

 

[ford390gashog]

Maybe its time to just ditch it! I would move to the always common 3G alternator. Parts are sold at all auto parts stores and the units are stone cold reliable! If I was you that is what I would do. Maybe I don't understand but why the huge urge to keep the LN alternator?

 

[typ4]

Regulator controls kick on IIRC, mine did the same thing in about 10k miles. Didnt mess with it , went with a 100amp 1g, 60k ago.
When they are finicky they are a pain, LN. I would say recheck the diodes.

 

[MIDNIGHT RIDER]

I can't speak for the smaller L-N units, such as the "ambulance" alternators, but the big Leece-Nevilles are THE WAY TO GO.

I run the 110-555 Leece-Neville and it is bullet-proof.

The regulator on my alternator is bigger than an entire 3G.




But then I can't say anything bad about the original old 1G relic that lived half-a-million-miles on my old 6.9 and another couple years on the Cummins.

I can now spin the pulley and it sounds like some kid's rattling amusement toy; but, right up to the day I took it out, it kept the three batteries charged and all the many lights bright, although I don't see how.

 

[Compu Doc]

You might want to read the information in this link.

http://news.prestolite.com/us/products/replace_7726JA_with_5523AA_alternator

Personally I would keep a Leece Neville product over the 3G system any day and I will probably do what is in the linked article. I was talking to an auto electric business that has been in business the past 40 years and they say that the heat is the culprit of these alternators killing the rectifiers. They recommended me going to a system that has external rectifiers. Not only will this be a better installation but will also be a 200 amp alternator.

http://www.prestolite.com/pgs_products/specs.php?item_detail_id=913&item=A0015523AA

 

[typ4]

And I totally forgot about that external upgrade, the midsize units dont like the heat. Thats what killed mine but it was a very old, 80 ish, J unit.