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Old 04-07-2019, 03:08 PM   #1
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Alternator alternative

Hi All. I have found a few old 2015 posts on this topic but am looking for fresh advice, if it is the same advice I am good with that too. I recently purchased a 2001 Monaco Diplomat 36D with an 8.3 ISC Cummins. The alternator worked on the drive home but has stopped charging, I am not getting an alt light on the dash and the tach still works (although it may not be driven off the alt). I have been reading that the Delco 28Si is a good replacement for the Leece-Neville 4884JB. However, the 28Si, appears to be a single wire self-exciting alternator. Does anyone have a wiring diagram or description on how to wire the new one?
Why replace it you ask? It isn't 18 years old, more moderns design, a replacement is under $150 and it puts out 200 amps.

Looking forward to your thoughts.

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Old 04-07-2019, 03:16 PM   #2
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I have read what your talking about here in the last few months . Thats all the help I have for now.

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Old 04-07-2019, 03:19 PM   #3
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I searched "28Si " in the search bar ...many hits on here
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Old 04-07-2019, 05:54 PM   #4
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Call these guys. Very knowledgable and have pretty much everything in stock. They had a refurbished Leece Neville in stock for my 03 HR and it was pretty cheap from what I remember.

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Old 04-07-2019, 06:58 PM   #5
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Call these guys with your alt part #

If you need a Duvac alternator, they offer It on the Delco

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Old 04-07-2019, 09:50 PM   #6
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Originally Posted by twinboat View Post
Call these guys with your alt part #

If you need a Duvac alternator, they offer It on the Delco

Thanks for the links.
This answers part of my question perhaps all of it.

Leece Neville 4800 - 4900 series (J mount and Pad mount

Mine is a J mount 4800 series. The 28Si has a "sense" treminal so it will work with the duvac isolator.
I will try and remember to take pictures and post my experience to help others.
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Old 04-08-2019, 06:35 AM   #7
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Recently replaced my alternator. I found the best price at Quality Power. I decided to replace my 160 amp Leece Neville with a 200 amp Delco Remy 28SI. The install was fairly simple except on the DR you don't connect the excite wire since it is self exciting. I had my old LN rebuilt and carry it as a spare.

Vera & Ken
1998 Holiday Rambler Imperial, RR8S Chassis
Cummins 6C8.3 mechanical engine, 325HP, 3060 Allison
Towing 2014 Ford Explorer
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Old 04-08-2019, 08:50 AM   #8
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My alternator failed, happened to be at home when I noticed so I just removed and had it rebuilt. Cost ~$180.

The only issue I had was I did find that even though I had all the battery disconnects off I was still getting voltage back to the alternator, found my solar was back feeding, pulled the fuses and this isolated the alternator from all voltage.
Jim J
2002 Monaco Windsor 38 PKD
2005 Jeep Grand Cherokee w/5.7 Hemi
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Old 04-13-2019, 05:39 PM   #9
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Alternator Alternatives

As promised post install attached are basic directions, use at your own risk

The swap was fairly straight forward.
Attached Files
File Type: pdf 8.3 ISC Leece-Neville 4884JB to Delco 28Si R&R.pdf (269.4 KB, 53 views)
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Old 04-13-2019, 07:19 PM   #10
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Nice, thanks for your efforts and write-up. Definitely goes in my "one of these days I'll need this" files.
2008 Camelot 40 PDQ
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Old 04-13-2019, 07:53 PM   #11
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Originally Posted by RustyTools View Post
Nice, thanks for your efforts and write-up. Definitely goes in my "one of these days I'll need this" files.
I couldn't find any instructions anywhere. So I figured let's get some out there.
I started out making a video but quickly realized that really takes a lot of time.
This rig is new to me and I am pretty sure has never been mechanicaly maintained. I have had a couple of P30 RV and always wanted a D pusher. Finally got one be it 18 yo but as long as there are Freightliner parts around I should be good.
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Old 04-14-2019, 01:32 PM   #12
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100 amp alternators, vs 130/160 amp
200 amp, 240/270 amp
270/300 amp alternators

OEM and most early model alternators for motorhomes are grossly underrated for the RV application.

Consider the typical power consumption by the exterior running lights and headlights. Each of those conventional little incandescent bulbs consumes 4 watts each and a typical motorhome has 15 of them. That’s 4x15 plus the line load = 60 watts.

The 1157 type running lights are 25 watts each, with 8 running across the front eyebrow (roof), two in the rear for running lights in the tail lights, bring the total to 10.

10x25 = 250 watts + 60 watts = 310 watts (26 amps) for running lights

Incandescent (Conventional) Headlights are power hungry. These standard bulbs typically demand 55 watts each – 110 watts total. Add in the line loads and losses and the power demand to run the headlights is something more than 120 watts (10 amps)

Exterior lights & Headlights = >/= 36 amps

Interior radio – the radio control head itself doesn’t use much power, typically 35 watts, but the surround sound amplifier system can consume 100-300 watts. It all depends on how much you crank up the sound to overcome the road noise and the snoring co-pilot.

Radio & Stereo – 235 watts (20 amps)

Miscellaneous equipment - DC Automatic Satellite Tracker system (2 amps), cell phone chargers (3 amps), GPS navigation system (3 amps), front mounted camera (1 amp), rear camera and 6x9 console display system (5 amps), engine control module (ECM) (10 amps), front air conditioner fan (10 amps), air conditioner compressor clutch (8 amps), windshield wipers (10 amps) and your refrigerator (even when its in LPG mode) uses (3-5 amps) which all equate to an additional (45-60 amps).

Add all of those conditions together
Lights = 36 amps
Radio = 20 amps
Misc Equipment = 52 amps
= 108 amps

Whats left? Battery Charging.

Arguably, batteries should be charged at a rate at least equal to or greater than their Reserve Capacity. Where the argument diverges is in the type of battery being recharged. Conventional batteries are harder to charge, (read: takes more wattage IN to get them to produce similar wattage OUT) and depending on the type of battery that can be more efficiently accomplished faster with a higher voltage. But higher voltages can cause harm to conventional batteries because the excess charge voltage gets dumped as heat. Heat will warp plates and boil the acid faster, calling for more frequent servicing.

A safe maximum charge voltage is 14.4 volts, however to achieve that charge voltage the amperage required from the charge source will be more than you might expect. More on this in a moment.

For a charger to actually reach the absorption charge voltage of 14.4 volts, the charger needs to be able to produce enough wattage out to cause the battery to reach a resistance level that allows the voltage to rise to the target voltage. Your charger might be putting out 14.4 volts as measured at the charger, but the voltage measured at the battery will be some number less, unless the charger and the wiring to it has enough wattage capacity to actually push that load into the batterie(s).

We already know based on the previous explanation that you are probably using 100 amps just running down the road at night. If its Daytime with your exterior lights off, you are still using about 70 amps of power.

What’s left is your charging capacity to recharge your start and house batteries.

If you have/had a 130 amp Delco-Remy 22Si alternator rated for 130 amps, you should expect that alternator to only produce that rated amperage when it is NEW, and at an operating rpm near 2000. Even then, the 130 amp rating will cause the alternator to reach its thermal limit, trip off, leaving your entire coach sucking off the start batteries as the alternator cools down and resets itself, trips back on and repeats the cycle. It will continue to do this until it either fails leaving you on the side of the road with a SES/ check engine light, or if you have your pilots license and/or a knack for paying attention to the steam gauge type VU meter on the dash that swings left of center when the alternator trips off, you start turning things unnecessary off before you find yourself sitting on the side of the road.

The stereo gets turned off. The spouse asks “why did you turn the radio off” and not to worry her, you provide some explanation that you are seeing if your alternator indicator will swing back into the positive side. They might play along with the experiment and pay some attention going forward. If your experiment works, you have found the threshold of the maximum your alternator is willing to put out before it overheats and trips off all together.

Should turning off the stereo not be enough, the AC blower fan and the AC itself is next, which will certainly peak the spouses interest because now we have gone from a loss of entertainment to a loss of creature comfort AND entertainment. This combination is most assuredly a guarantee to peak the entire family’s interest, especially considering pushing the RV off the side of the Road is not an option.

If your coach has been sitting without a battery recharging system for MONTHS keeping it topped off AND you start the engine, pull on the headlights and running lights, turn up the radio and kick on the airconditioner to high, your load demand will be everything your OEM alternator can produce. This is true for any alternator rated up to and beyond 240 amps.

Let me explain where the other 140 amps gets used if you haven’t already figured it out.

Like we covered in the preceding, your load demand at initial startup will exceed 100 amps. That load demand will not diminish as you drive down the highway at night with the AC on and the stereo cranking.

Your start batteries are more than likely have a Reserve Capacity at or near 170 amps EACH. Your alternator will push as many amps into your start batteries as they’ll initially take, and if you have two start batteries with 170 Ah of reserve capacity, this means your 130-240 amp alternator will reach 100% load immediately.

Depending on its amp rating, how badly discharged your start batteries actually are, and if your house batteries are tied into the alternator circuit in any way, your alternator will be maxed out for HOURS. MANY HOURS. Probably ALL NIGHT.

Most alternators aren’t designed to operate at 100% load for an hour, much less several hours.

So whats the solution?

There are three solutions.

(1) Install a Delco-Remy 40Si 300 amp alternator with remote sense. It will cover the 100 amp comfort demand of driving at night, plus it can provide the 170 amp charge to the start batteries and still have enough left over to start the recharge of the depleted house battery bank.

(2) If you have two start batteries with 170 amp RC EACH; Install at least 600 watts of solar on the roof and have it keep your batteries charged to 100% SOC. A 600 watt system will actually produce about 300 watts on average over a typical solar day. This amount of wattage is enough to offset the standard depletion rate of two conventional start batteries, making the OEM alternator not have to kill itself trying to recharge a near dead set of start batteries with only 30-60 amps of load capacity left over after everything else places its demands on the system.
(3) Start your travels during the day with all of your lights off. Make sure you can drive in this condition for at least 4 hours with your lights off. Pay attention to your amp meter. After 2 hours on the road see if adding any other load will cause the dash meter to move. If it moves left by as much as one thickness of the needle, or if it ever moves left of center, or left of 13 volts DC, consider that the alternator amperage load limit and don’t add any more load.
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Old 04-14-2019, 06:09 PM   #13
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The smartest thing I did was replace the 200 amp alt. On my 8.3 Cummins with a self
Excited alt. Just taped up the excited wire from its relay.
Did this after loosing alt. Output in dead of night leaving Seattle for Billings. Ran generator with the battery jumper relay held down on the dash. Crossing 4th of
July pass hit a good pot hole and engine alt. Came back on....
So I put a stop to that, replaced block heater the same time.
I’d have to look up my records to see what alt I used, do know that I had new alt
Modified with bigger rated diode plate.
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Old 04-15-2019, 08:50 AM   #14
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Thanks for the power consumption rundown. I do keep my coach batteries topped up when on shore power with an automatic 2 amp charger. I was looking over the output report for the new alternator it looks like it is 200 amp nominal spinning around 26-28k RPM. If the ratio between the crankshaft and alternator rotor is 3:1 at 1200 engine RPM the rotor would be spinning at 3600 RPM. I am guessing on the ratio. That should produce around 220 amps minus wire drop resistance etc.
Solar is an excellent option as well. PV cells are pretty efficient these days, great for boondocking too.
Attached Files
File Type: pdf AlternatorOutput28Si.pdf (267.8 KB, 21 views)

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