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Old 03-01-2006, 07:10 PM   #15
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There is some mention of dual alternator brackets at www.4alterstart.com. Maybe they have ideas about how this should be done. I've spoken to two fellow there and they were both quite helpful.
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Old 03-01-2006, 07:12 PM   #16
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Have the Aux Alt charge the house batteries

Why not wire your second alternator to charge only the two house batteries? That will allow the main alternator to charge the main battery, as well as run the secondary engine systems. Those secondary systems are a huge load on an alternator, and if you take them away from the second alternator, you would probably be equalising the load between the two somewhat.
Headlights are about 7 amps or so, the clearance lights another 3 or more amps, the electric fuel pump can draw up to 10 amps, and the A/C compressor on the engine, and the interior fans to blow cool air on you are another 20 amps. That is 50 amps, not counting operating the ECM (computer) and ignition system.
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Old 03-01-2006, 07:28 PM   #17
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I'm with Terry, if you are going to go to the trouble of a second alternator, I'd use one for the house batteries and one for the chassis battery. With this setup one could also do away with the isolator box that allows the one alternator to feed the two battery sets. Downside may be the belting arrangement on the engine. I don't think a single v belt could handle the two alternators, one of the ribbed belt setups as used on later 454's might do it but I can see where one may get into a lot of parts replacements to get this setup to work. And of course there will be some wiring required to feed the battery banks separately.

I think its definitely doable, but I'm not sure it would be worth all the work for me.....

Just my 2 cents (Canadian !)
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Old 03-01-2006, 08:11 PM   #18
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Two Alternators

Don,t do it. You could have a major burn out if one should put out more amps or voltage then it would backfeed into
the other and blow out the diodes.

Better to buy a larger alternator
and stay with just one,

Pat370
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Old 03-01-2006, 09:02 PM   #19
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Quote:
Originally Posted by Pat370
Don,t do it. You could have a major burn out if one should put out more amps or voltage then it would backfeed into
the other and blow out the diodes.

Better to buy a larger alternator
and stay with just one,

Pat370
That's the advantage with my scheme. The two systems are completely seperate, with no chance of backfeeding since they are completely seperate. The disadvantage is the second alternator would be run by a very thin belt driven by the water pump.
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Old 03-01-2006, 09:14 PM   #20
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Alternators are a DRAG...on the engine. Why not figure out your true maximum load, add say 25% or so and get the right alternator for the job?
Big alternators take quite a bit of horsepower to drive. This has an effect on how your motor runs, cools, and gives you economy.
Overkill on the alternator may not be in your best interst .... go for the proper size in MHO.
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Old 03-01-2006, 09:26 PM   #21
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I have had a local alternator/generator shop run by one man rebuilding my starters and alternators for the last 15 years. I've only had to take one back and it was because of a stripped out screw in the aluminum case. From what he has told me and what I have found on the www.pickuptrucks.com forum is that 140 amps is the highest amount you can safely run in a small case Delco style case. The 140 can be really rough on the case so that is why there is an "iceburg" version with a more open case and rear ball bearings for the shaft. This is advertised through J.C. Whitney and other sites. He told me it would be better to convert to the large case alternator and go up from 175 to 235 amps or so. I'm running 105 amps now and should the alternator fail, I will upgrade to a large case with probably 200 amps. He says that he pulls the standard alternators off GM vehicles and installs large case alternators he has rebuilt when ambulance companies bring their new vehicles in to him. This sounds like just the ticket for your situation.
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Old 03-01-2006, 09:37 PM   #22
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Glen,
I agree alternators can use up lots of horsepower but ONLY when they are generating lots of amps.

I see to recall from an expeience at some science museum that if you hand crank an alternator with no load it will be easy to turn, start adding loads and it will become progressively harder.

I don't believe there is any significant difference in horsepower required to produce 50 amps at 13.2 volts by an alternator with a 200 amp max capacity vs a 100 amp max capacity.

We have some very knowledgible folks on the Forum so I imagine someone will confirm or correct my statement.
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Old 03-01-2006, 11:10 PM   #23
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Here is what you use for dual alt's to protect your circut. This is what we would instal on over the road trucks that needed dual alt's to run all the hundreds of chicken lights on there rigs..



Dual Alternator Rated The SAR-V3 Regulator is rated to drive the fields of two alternators in parallel. No additional circuitry is required if both alternators are mounted on the same engine. When the alternators are mounted on separate engines, a Dual Alternator Controller, DAC, is available which permits either or both engines to be run without applying field power to an alternator that isn't rotating. ://www.amplepower.com
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Old 03-03-2006, 05:52 PM   #24
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Replacement alternators

A further update to my notes above regarding alternator replacement. The alt that went in the 1991 350 (454) this afternoon was a Talon rebuild, 105 Amp, which is what I could get. The Talon number is 66083N, and it seems to have been designed for a series of 1987-1988 Chevrolet Camaros, Caprices, and Pontiac Firebirds, mostly 350's and 305's. It came with a nice computer generated graph showing output from 1K to 6K RPM, so I know it worked when it went in.

An idle question: On my 454, bolted to the alternator bracket, and sitting just under the upper radiator hose, between the hose and the engine block, is a rectangular black box with a small red wire coming out of it. This box has two vertical screws or bolts through the top and what appear to be two unused threaded studs protruding from the engine front side of the box. It appears ( could be wrong on this one--lots of wire bundles around there) that a #10 or #8 red wire also came out of the box at one time and was attached to the positive output on the alternator, but the spade on the wire is now broken. I haven't checked to see if the wire is hot.

Does anyone know the purpose of this box? I can probably provide a picture tomorrow if needed.

Best,

Rob Alley
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Old 03-03-2006, 10:49 PM   #25
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Rob,
Is it a relay looking thingy?
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Old 03-03-2006, 10:53 PM   #26
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Quote:
Originally Posted by overlander63
The disadvantage is the second alternator would be run by a very thin belt driven by the water pump.
I think if one could figure out how to mount the second alternator where the passenger side AIR pump currently sits (under the existing alternator) you could just pickup the current serpentine style belt thats there already...bascially you could replace one (currently unsed) accessory for another, driven from the same belt that's already there.
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Old 04-21-2006, 10:59 AM   #27
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Volt Gauge and Alternator Update

I replaced the alternator with the 250 amp large frame alternator from http://www.4alterstart.com/. The part number is 8112-5-250A SP-W1201. It has been installed for about 7 weeks now and seems to be performing just fine. The only surprise I had was that it has a 2 year warranty, not a lifetime as I thought. Many of their products do have lifetime warranties, but not this one. I didn't notice/realize this when I ordered it. If I had, I MIGHT have tried to find a local alternative rather than paying $400 plus $75 shipping. No hard feelings on my part, just a heads up.

After installing the new alternator, my volt gauge still was reading 12.5 or so but the shop assured me that alternator output was between 13.8 and 14.4 so I asked them to figure out why the bad reading on the gauge. They poked around and ran a new wire but the reading was still low, so I ordered a new gauge from, you guessed it, http://www.custominstrumentpanels.com/index.html. Shop installed it and it read the same as the old one. They determined that for some reason the voltage they were getting from the output side of the ignition switch did not correctly reflect the voltage at the batteries, so they put in a wire from the battery terminal to the volt gauge which is controlled by a relay which closes when the ignition is on. (so the the gauge is only energized when the key is on). The gauge now read 13.8 to 14.4 as it should.

I suspect the low voltage going to the dash has something to do with the intermittent and nonsensical illumination of my low coolant light. But more on that in another thread.
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Old 04-21-2006, 06:08 PM   #28
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High output alternator source

Greetings,

My old Suburban ('82) had a weak alternator. I researched the 'net and found the following place, http://www.wranglernw.com/commerce/default.asp ,
which was able to answer my questions, ID the correct alternator, and provide the necessary adaptor wiring necessary to install the replacement alternator. Price was reasonable (though not cheap) and the service was impeccable.

I have since replaced my Suburban with a slightly newer version (1991) and I am very pleased. The alternator in the newer Suburban is of a newer design and seems to hold the necessary power to keep my truck and dual battery trailer happy!
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