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Old 07-28-2019, 01:04 PM   #29
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Ok, first I dont have much experience with this, but could all of the alternator problems have started with the solar panels back feeding the alternator?

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Old 07-28-2019, 05:17 PM   #30
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I found the fuse to the DUVAC terminal was blown and replaced it. Then I put the 28si back on and had same problem that it would not shut off. I researched the net some more and noted some comments about needing a 4 pin battery isolator to use the 28si. As noted earlier in this thread my battery isolator (Big Boy) has been replaced with a continuous solenoid relay. So I decided to reinstall the new L-N alternator. However, again it did not provide any juice (alternator light on and Aladdin showing 11.9 volts), even though the DUVAC terminal now showed current flow. Thought...well maybe this new alternator (purchased on Amazon) is not good. So reinstall the original alternator that shop had indicated was good after testing. Yep...you guessed it, works perfect!
So after several days of sweating in the hot sun changing the alternator (estimate at least 10 changes), hours on the internet, I have advanced to the starting point???
So other than becoming much more familiar with the electrical panel, fuse locations and proficient at changing the alternator I have not accomplished much. I'll return the amazon alternator (20% charge), and research a little more on the installation of the 28si. My impression is the the 28si is a superior alternator primarily because it will operate in a hotter environment. The L-N has one external fan with a published top operating range of 230+ and the 28si has two internal fans with a published operating range of 250+. If these alternators are thermal protected, then I rationalize high temps may be causing the the alternator to kick on and off. I have been running hot (195-200 on the flat) have never heard the roar of a fan kicking on. Was not sure what was normal but based on readings so far that may be a bit excessive. Also, I first noted the alternator light after sitting at idle with maybe little air moving around in the top of the engine compartment (if fan not functioning correctly). So I will let the alternator rest for now...or maybe I just need to rest. Thanks for all the responses and I will be back with more questions.

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Old 07-29-2019, 11:12 AM   #31
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Thanks Ken and George!!! I reinstalled the Delco 28si leaving the ignition wire off and everything works as it should. Good current per Aladdin (14.1), tach works, no alternator light and engine shuts off. SO LESSON LEARNED...IF YOU INSTALLED OR HAD INSTALLED A NEW ALTERNATOR AND ENGINE WILL NOT SHUT OFF REMOVE THE IGNITION WIRE FROM THE ALTERNATOR.
Thanks again
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Old 07-30-2019, 06:33 AM   #32
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Does your BIRD still charge your house batteries?
This post is my opinion, worth what you paid for it.
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Old 07-30-2019, 08:43 AM   #33
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Not sure what the acronym BIRD stands for??? Everything seems to work. My alternator is charging both the house and chassis batteries and the converter is charging.
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Old 08-04-2019, 04:15 PM   #34
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Battery control center

Had a similar problem and stopped to have an independent tech replace the alternator. It did not fix the problem. It turns out that a wire to the Battery Control Center was loose. Tightened it down and check regularly. No problem in two years.
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Old 08-04-2019, 04:46 PM   #35
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Take your unit to any nationwide auto parts store (O'Reillys, etc). They will check your batteries and alternator and suggest repairs. Alternators and batteries are easy to change, if that's your problem.

Hint: if it's the alternator, make a drawing of how the serpentine belt is attached before you replace the alternator.
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Old 08-04-2019, 05:48 PM   #36
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Originally Posted by dca81 View Post
Not sure what the acronym BIRD stands for??? Everything seems to work. My alternator is charging both the house and chassis batteries and the converter is charging.
BIRD = Bi-directional Isolation Relay with Delay.

It monitors your charging systems and isolates or connects the 2 battery banks together ( house & chassis ) if a charging source is detected on one or the other.
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Old 08-04-2019, 09:47 PM   #37
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The alternator light going on/off COULD be reflecting a very high draw on the electrical system, IE a short circuit somewhere. IF the alternator output is stable at 13.7 to 14.2 with the engine running and no other 12V loads from the coach, you got a short. Alternators typically don't just go intermittently go bad. The dash light indicates low system voltage, as do your other fault lights.
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Old 08-05-2019, 10:19 AM   #38
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Alternator was replaced with a Delco 28si with the ignition wire left unconnected. Took on a 50 mile test drive and everything functions as it should. Real test will come when we drive to visit son and family in Seattle.
Thanks for all the suggestions and input.
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Old 08-09-2019, 02:04 AM   #39
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A little late to the party, but wanted to make some comments that might help others in the future regarding the various terminals on 24SI & 28SI...

- I Terminal: Before the alternator is "running", it will connect an indicator light to ground to turn it on. Once it's "running", it can provide up to 1A of current. The L-N units may not work the same, and that 1A from 24/28SI may be keeping fuel solenoids, etc. on preventing shut-off. On the 24SI & 28SI, this connection is not required (unless you want indicator light function). As someone said, they are "self-excited" and will sense rotation and turn on at around 1,100 alternator RPM (about 3x engine speed).

- Remote Sense: If not connected, the alternator regulates Voltage at the output terminal. If connected, it will regulate from that signal. It's designed to compensate for long cable runs to the battery, or for the voltage drop going through an isolator.

The alternators are not thermally protected. They simply have components that can withstand running at the rated temperatures (BTW, this is air temperature, not alternator temperature). They won't instantly die if run at hotter conditions, they just don't last as long...and yes, they are tested to run for loooong periods at those rated temperatures.

I have not measured the air temperature in the engine compartment of my 1990 DP, but I suspect it's not too high with a side radiator and another opening on the curb side.

As for mounting dimensions and pulley location, as long as all the parts are there (including the slinger and washer on the 24/28SI), you can move the pulley from your old unit to the new one and it will line up.
The mounting for all heavy duty alternators, with VERY few exceptions, are designed to me mechanically interchangeable: Hinge for Hinge, and Pad for Pad mounts.

I still have the Leece-Neville 160A unit, and hope to not have to mess with it. If I do, it will get a 28SI 180A unit going in there :-)

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