What's a good size alternator?

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natjwest

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I am on the road now in San Francisco, getting my alternator replaced. Yesterday's symptoms were freaky turn signals, radio clock blinking on/off, dashboard voltage gauge getting into the orange (bad), truck failed to start at a pit stop requiring a jump start, the auto transmission would not shift out of first gear, and finally the revs would jump around like the fuel injector was freaking. This morning after a rest, it fired just fine and everything ran normally for about 20 minutes when (I think) the alternator heated up and the turn signals started blinking fast/slow/freaky. Oh and the tachometer gauge has been acting freaky for a little while. I read elsewhere on a Chevy forum that my truck's tach is run off the alternator so that should have been a signal to me, duh.

The shop has the truck now and found low voltage coming from the alternator at idle and at revs, just like I suspected. They ruled out the Surepower isolator (12023A).

There was a remanufactured Delco, I believe 100 amp in there. I am getting another "stock" 100/105 amp put in since I'm on short notice. I am wondering if it is wise to get a bigger amperage alternator when I get back home, something in the 170 range.

Right now, I don't have a solar panel, but might in the future. I have two batteries in the truck (which is a 2000 K2500 diesel) and two in the camper (Interstate flooded lead). This whole incident started at 6 AM yesterday morning (15 degs) where I had run the furnace practically all night. In the morning, I still had power to run DC lights and water pump but my Cobra 1000 watt inverter wouldn't run and said "low power" and that's the only way I can get a voltage reading, so the camper batteries were quite low.

On the truck side, the old Detroit diesel took four separate crank attempts to finally fire up so I'm sure the truck batteries were quite low. (Hard to start in the cold is a possibly separate issue I will bring up with my proper diesel mechanic upon return home.) Having to charge four batteries (two dead, two low) was apparently too much for my alternator.

I will most definitely find myself in a similar situation with two very low camper batteries in the future and will require the alternator to power them up. What size alternator should I use? I'll be upgrading the wires while I'm at it.

Oh and here's a picture since I know you guys like pics.
DSC_8632_resized.jpg
 
These have a very good reputation in the diesel world.

http://www.dbelectrical.com/

An important spec to consider is how much the alt. puts out at idle vs running speed.

I would suggest something in the 140-160A range.

You might check ebay.
 
Use a stock alaternator (in terms of specifications) on your truck. When alternators are rewound to enable higher than about 100 amps, the cooling capacity of a standard size alternator is not adquate due to the physical size heat dissipation limits. Liquid cooled alternators are being used where higher capasity 12VDC charging systems are required. Obviously, modifications must be made to upgrade to a liquid cooled alternator. Phyically larger alterntors can sustain higher capacities but they are expensive too and require a modified mounting bracked. In addition, when a vehicle is modified, replacement parts may not be readily available in places such as the Alaska Highway in the Yukon.

The best system is a dual alterntor setup, using two standard alternators, stock for your vehicle. The second alternator powers a completely separate charging system for the camper house system and provides a spare should it be needed for the truck system. A system like this requires no isolator systems, electronic or otherwise. The truck system remains completely stock, just as designed by your truck manufacturer. Thus, your truck system, more important in remote areas, is more reliable becaue it has not been "tampered" with.

There are a problems with dual alternators too, finding an accessory bracket for your truck that will accomodate two alternators. This mounting brack may be available from the dealer parts department, but probably it will be necessary to find an aftermarket supplier.

There is no perfect solution, but stock alternators are nearly always better in the long run.


John
 
With higher amp alternators you also need to see what RPM they are rating them at AND what they put out at low rpm's/idle. Most I've seen do a poor job at idle/low rpm's - which is where your diesel spends most of it's life....

Go with a quality stock rated unit and you should be good for another 10 years.
 
Thanks for the advice. I was really hoping to hear that my stock 100 amp alternator won't need upgrading. The shop that did the work raved about the remanufacturing facility and how awesome the alternators are. The owner claimed a "lifetime warranty", not so sure about that. What I am sure about is $170 for the unit, about $100 more than I've seen them online. But that's the price to pay when in need.
 
Thanks for the advice. I was really hoping to hear that my stock 100 amp alternator won't need upgrading. The shop that did the work raved about the remanufacturing facility and how awesome the alternators are. The owner claimed a "lifetime warranty", not so sure about that. What I am sure about is $170 for the unit, about $100 more than I've seen them online. But that's the price to pay when in need.



besides.....isnt your camper on a 30 amp thermal breaker? fwc puts one under the hood to protect their wiring.

my guess is that as long as your headlights are off that alternator will do just fine.....the breaker will cycle if the camper batteries draw 30 amps.....limiting max power draw for those dead camper batteries.


with you headlights on the alternator will probably be maxed out.

high performance alternators are available, and regulate to the gnats ass even at low rpm. they just cost more.
 
What about the picture???? Sure is not San Francisco. Some where on the East side of the Sierra's?

Good eye, it's the PV Pit BLM campground just north of Bishop.

My new 100 amp alt just died, putting out 11.3 volts at idle and the batteries are being used to power the truck. They show a voltage drop when the truck is running.

I am going to Autozone now for a 140 amp gold lifetime warranty alt, and will have a mechanic put it in, unless someone can tell me how to get the tensioner pulley at the proper tightness. I've never done tensioner business on a serpentine belt.
 
Good eye, it's the PV Pit BLM campground just north of Bishop.

My new 100 amp alt just died, putting out 11.3 volts at idle and the batteries are being used to power the truck. They show a voltage drop when the truck is running.

I am going to Autozone now for a 140 amp gold lifetime warranty alt, and will have a mechanic put it in, unless someone can tell me how to get the tensioner pulley at the proper tightness. I've never done tensioner business on a serpentine belt.


The new one just died? Would make me want to start looking around for another culprit like voltage regulator or something.

Anyways serpentine belts are easy, esp. if its one of the spring loaded ones. The spring loaded ones you just turn the center bolt with a wrench to retract it to take the belt on/off. If its one where you pivot the alt you just get everything in place then use a pry bar to pull tension on the alt. while you snug up the bolt that holds it in place.
 
I'm thinking something is up with the truck and not the alternator(s). I new alternator shouldn't die right away.


I had an issue with my alternator - it was a worn wire popping the 120amp super fuse under the hood. Everything pointed to the alternator - but it was really justa fuse....
 
Unsure about other things but I just got home after 1000 miles on the new-new alternator. I upgraded the alternator-to-batt wire to proper 4 ga. The previous owner installed the Surepower isolator and wired it up with 12 ga (!) wire from alt to iso to batt. That may have contributed to the problem. I wired-out the Surepower for the return voyage and for the first time in a year that I've owned the truck, the volt gauge on the dash shows over 14 volts. I think I've solved a couple problems at once.

I do need to get a different isolator since the 12023A is not rated for my 140 amp alternator. Surepower tech support says I need to upgrade, but they also confirmed that the voltage drop is .8 to 1.0 on their isolators. I can't handle that so I'm looking at a big-ass switch to bypass the Surepower for most driving or possibly a Hellroaring unit.
 
I did the simple approch for charging the camper, came off the truck battery with 8gauge wire fused with 50 amp breaker, then wired into a continues duty solenoid, wired so its on when truck is switched on. and wire run to camper from there.
 
check dc power engeneering.
they are in cali
I just got their 270 amp unit.
read their web site, they are brand new units, engineered as high power units, not upgraded.
they also have dual alternator brackets.
I haven't installed it yet, but the altenator impressed me when I received it. I won't get into the details why I ordered it, but my alternator is dying a slow death. I'm swapping the alternator and keeping the stock as a backup spare.
give them a call
Talk to stan8884410144
www.dcpowerinc.com
 
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