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Thread: OT: larger alternator on truck
01-22-2010, 02:42 PM #1
OT: larger alternator on truck
I would like to put a larger (more amp) alternator on my truck. Go from 95 to 135 amp. I do not need more amps but the bigger ones will put out more amps at idle. If I do this would i have to replace the main output cable as well. I figure it will only be max output for a minute or two after starting. No extra loads added that where not stock with the smaller alternator.
01-22-2010, 02:56 PM #2
You may want to look into an overdrive pulley. Also upgrading the cables from the alt. to the battery, ground to the frame, and ground to the block with atleast 4 gauge wire. Here is a link to a write up on doing this.
01-22-2010, 03:13 PM #3I do not need more amps but the bigger ones will put out more amps at idle.
01-22-2010, 03:25 PM #4
If the truck was originally available with the larger alternator as an option, it's probably wired for it.
If your battery needs to pull over 95 amps after starting, it's time for a tune-up
01-22-2010, 04:04 PM #5
Very seldom will you ever see a car with a alternator wire bigger than 8 awg. I have asked some of the aftermarket harness makers about this apparent discrepancy and I have never gotten a logical answer. For the bigger alternators the amperage charts would lead you to believe you should be using welding lead cables. But the OEM car manufacturers consistently use the smaller gages without any apparent problems. Larger gage wires are sometimes used in cars and airplanes, to limit voltage drop due to a long distance between the battery and the starter (car with battery in the trunk, airplane with battery toward the tail). Based on this empirical experience, the alternators, regardless of size, must not spend very much time at high amperages. Another indication that this is the case (alternators don't spend very much time at high amperages) is the industrial size battery chargers seldom go above 6o amps for charging the battery and are limited to a couple of minutes at the "boost" settings to start the car. Failure to heed the restriction on the "boost settings (typically around 200 amps) will damage the battery according to the warning labels. A car with a good battery and a good alternator will spend only a few minutes re-charging a discharged battery and the amperages probably won't exceed 20 amps for long. The alternator only needs to put out a couple of amps beyond what the car's electrical system is using to keep the battery happy. So, unless you have a huge music amp system on the truck or other high amperage load, the main advantage of a larger alternator will be to extend the alternators life. Thus the main advantage to the larger alternators is that the diodes run cooler which makes the alternator less prone to fail (bad diodes are the leading cause of alternator failure). IMHO you can make the change without changing the alternator wire.
01-22-2010, 05:31 PM #6
The gauge wire required depends on the ventilation. Notice the small wires from the power transformers on poles and the heavy wires going into the weatherhead of a building. If you put those small wires inside conduit sealed in a wall, they would be gone in a flash. The answer to your question depends in large part on where the wires are and how long they are.
Last edited by 9100; 01-22-2010 at 05:34 PM. Reason: spelling
01-22-2010, 05:39 PM #7
I have 130A 3G/4G Ford alternators on all the vehicles, tractor and dozer I own. I believe the factory uses a 6 gauge wire for the power terminal on these. They're well made units, a brush and regulator changeout takes 2 minutes and costs $10. They have excellent idle voltage output and are easily set up for one wire operation. There's atleast a half dozen different case configurations to fit most mounting styles.
01-22-2010, 07:27 PM #8
Where aren the Ford brush and regulator kits available? Dealership only?
01-22-2010, 08:25 PM #9
I buy stuff like that from automotive express delivery, a local wholesaler that delievers to my shop.
I've never actually had to buy one, but I'm one of those that likes to consider all angles before deaming a retrofit component acceptable. The 3G/4G uses off the shelf, common stock sealed bearings that can be found anywhere and one of the cheapest and definitely easiest to change brush/reg assemblies.
01-22-2010, 10:14 PM #10
Garwood this is a ford ranger with what I believe is a 3g Alternator. I am hoping that new brushes will solve the problem but , IF the commutator looks bad I was thinking if I have to replace the entire alternator I might as well get a bigger one. The curve I saw for this unit shows zero amps at 1000 rpm while the 135 amp unit has a few amps output at the same rpm.
This voltmeter never moved after the engine was running before. With the new battery I can see the needle move as I turn electrical loads on/off. So I am not sure, the new battery may have a problem. I think i will take some time to shop around for prices.
Any thoughts on how to identify a higher amp alternator at the wrecking yard?
01-22-2010, 10:39 PM #11
As the 3g/4g's go I believe the 130 amp units have a pattern of three pairs of two large (5/16?) holes surrounding the pulley while the lessor units have patterns of groups of three or four smaller holse surrounding the pulley.
The engines I run them on idle between 750 and 800 and the 3g/4g 130's put out over 14 volts at that speed. I retrofit custom Cummins diesel drivetrains into all sorts of things and a few years ago experienced a big downturn in the quality of remanufactured alternators and electrical parts for vehicles more than 15 years old (china/india parts likely). I did some research and hands on tests of common modern alternators and was most impressed with the 3G's. They handle severe conditions, vibration, excessive belt tension and they're cheap and affordable. I think a brand new one (130A) runs about $120, no core needed.
I think the thing about the 3G (and Ford) that's sorta neat is they're idiot proof. Ford hasn't changed the color coding of thier charging wiring in 60+ years. If you need to hook a 3G up under the hood of a 1960's truck the keyed 12V is the same color as the pigtail from a 2009 vehicle.
01-22-2010, 11:34 PM #12
when the performance curve rates it at 1000rpm that is alternator rpm
not engine rpm
usually the alternator is ratio'd up to around 2.5 to as much as 3 : 1
so if the engine is idling at 650 it is turning the alternator well over cutin and it should be charging enough to cover all oem loads and charge a good battery.
nothing wrong with a higher output alternator, but i wouldn't automatically jump up to one if i didn't have a need for it.
the 3g alternator was used by ford on their L8000 with 8.3 liter
cummins, that was the biggest joke i ever saw
they engineered it with a single 8 groove serp to drive everything
including the hd air clutch fan, which over time with it cycling on
and off again would over stress the rear brg of the alternator and spit it out on the ground.
never had a new alternator from ford last over 6 months and even my best rebuilder could not make one to last over 8 months.
finally convinced the customer to change the mount brkt to a large frame leece neville and ended the issue.
car manufactures should not be allowed to build heavy trucks!
for light duty trucks, the 3g and 4g are more than adequate, certainly
better than the delco cs130 when it comes to service/repair
01-23-2010, 03:09 AM #13
Like my Nippendenso's
A set of brushes and bearings every 100K and good to go...
No Ford Stuff on my Cummins
Work on them all ..
Hate Ford electrics.. Puny Ignition switches, Distributor modules, Hall pickups, stupid location of reverse switch on F350's down in the salt etc...
01-23-2010, 07:38 AM #14
My son has a 2002 Madza B3000 4x4 (manual transmission FTW). It's a Ford Ranger in classier livery. His OE 90amp alternator failed recently, and I just threw the 130 amp upgrade in without a thought about wiring upgrades.
I presume the Ford factory where this truck was built had ONE type of wiring harness for the given engine and two alternator choices from the factory. Since the bigger alternator bolted right in and didn't even require a belt change, I figure it's safe. No problems at all so far. The only difference he's noticed is that the headlights no longer dim when he turns on his aftermarket stereo.
01-23-2010, 07:44 AM #15
I just changed my alternator on my S10 with a 4.3 liter. The good thing in my case is the 4.3 matches up directly some 350 parts. A lot of people on the S10 forum had talked of just using alternators off of later model full size trucks which had 135 amp units. It was plug and play, but regardless no other wires needed to be upgraded.
01-23-2010, 11:24 AM #16
I have always heard that you could rebuild an alternator one time with no problems. just replace the brushes and it should last another 80,000 miles. Is this true with modern cars. Is there enough metal to smooth out the ridges/groves worn into the commutator or do you even have to do that? I would replace the bearing while it is out anyway.
The local wrecking yard sells alternators for $18.00. so new brushes and bearing cost another $20 or so.
Kragen wants $120 just for the alternator and the regulator/brushes are $60. And I bet they will not give me back the core charge since I would be returning smaller unit.
01-23-2010, 11:31 AM #17
A smaller pulley on the alternator will reach it's max output faster, but will not increase max output. The average alternator reaches peak output around the rpms it takes to go 60-70mph. Not sure why you are having a problem. I have a boat load of undersized pulleys from a JERK customer who I cut off for slow payment. They are 6061 and were going to get anodized, if I could match you up, I would send a couple to you for shipping charges only. If left with out anodizing they only last 50,000 miles or so. I used to sell and build high output charging systems for limousines and have some knowledge about charging system issues. Using a pulley that is too small can lower bearing life, through lots of field testing the correct size to over drive the alternator with out hurting bearing life was determined. Pm me if you would like to discuss further.
01-23-2010, 12:02 PM #18
An alternator shop should be able to upgrade your existing alternator. That's what they did to mine, 65 to 125 amps in the stock alternator housing (built a camper out of my truck, so I added 2 240 Ah batteries)
The higher output alternators do not give more amps at idle though. They warned me that the voltage would be lower than expected at idle.
I agree with knudsen though, if your battery needs more than 95 amps after starting, it probably time to replace it
01-23-2010, 12:10 PM #19
I just realized this truck has a volt meter not an amp meter. So it is low voltage at hot idle. I guess the amps are probably good and if a high amp alternator would have lower idle voltage I guess I should just rebuild this one.
PS: I looked for the idle amp graph and no luck so far. Now I have to find a idle volt graph.
01-23-2010, 12:27 PM #20