• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Dual Alternator Setup

F

fastjohnny

Member
Messages
196
Reaction score
0
Location
SW Michigan
Background info: My 99 suburban has become my favorite plow vehicle over my 02 Duramax, for a couple reasons including shorter wheelbase and the 4L80 is much quicker in reverse than the Ally. What I have not been fond of was the dismal stock 105A CS130D alternator, which could not keep up with continuous plow duty.

I had picked up an AD244 like found on my Duramax, and was about ready to swap it in when I got the hankering to just go with dual alternators. Research indicated it was a factory option, part numbers where located, but alas, the alternator bracket is no longer to be found via any GM sources.

Not ready to give up this idea, I did some further digging and found a couple decent pictures of said bracket, which I printed and resized until I had a reasonable full scale pattern, matching my alternator bolt spacing. I traced this pattern on a scrap piece of .027 aluminum coil stock for a more durable template. I used a 3/16" steel plate for the bracket which I cut using plasma, dressed with grinder as needed, and drilled all mounting holes, and welded a nut for the new belt idler pulley. A little bit of work with a die grinder was needed due to some variance in my pattern, but all things considered, it fit very well, and the new alternator bolted up fine.

I had a little hickup on the belt length: the 120"+/- belt spec for dual alternators were for 2 of the small frame alternators, not one large (the added AD 244) and one small. A bit of dumb luck here, the vac pump is not needed, as I have a TM, but had never removed the vac pump. Removing this allowed the belt to fit.

Results: Nothing short of awesome. I can run all accessories, lights including HID's which now don't flicker when I use the plow. Where the volt gauge would dip down and slowly return to <14volts, now it will dip with plow motor running, but pop right up to 14v as soon as the plow motor stops. Also because the alternators are keeping the batteries fully charged, cold startups are no problem, 6degrees today, fired right over, with one glow cycle and no block heater use.

One oddity: For alternator excite, I had a single brown wire on a 4 terminal plug that fit my alternator from an old alternator. I tapped this into the brown wire on the existing alternator, which uses the same plug but has an additional wire which powers the tach to my understanding. My tach will read fine at idle, on start up, and when driving, but after awhile, the tach will get funky, when I let off the gas, it will drop to 0rpm. When I'm on the gas, it reads normal. Any thoughts on this?

Now because of my impatience, I have a spare idler pulley and belt, as I had ordered from GM, but got antsy to get it done, and picked up an idler from NAPA and a belt from Autozone. If I get energetic and/or someone really wants dual alts, I might be convinced to make another bracket, and sell with pulley and belt for a kit.

Pics forthcoming.
 
Dual alternators is probably something I could use, I have two batteries in the truck and when I tow our travel trailer there is another two batteries. I do keep those two on a trickle charger but that's not possible when coming home from boondocking. I do have a Honda generator which helps when we don't have 110 to plug into. What I would like to know is can one not take a stock alternator and have it rebuilt to put out 200 or more amps. For someone like me without the fabrication skills or tools then that might be an option. I am pretty sure my present alternator is 130 amps but could be wrong.
 
You have to have different size pulleys or some other way to make one alt the lead and the other one the lag alternator. This can be as simple as putting the "remote voltage sense" wire at different locations. Otherwise they can fight each other as one brings up the voltage the other drops off and this oscillates between them. This "fighting" can confuse a regulator and have it shut down the alternator from over-voltage thinking it has failed. One alternator brings the voltage up - what is the second unit going to think if it isn't bringing up the voltage? What if both command higher voltage- the voltage jumps and they both respond with lower voltage causing your voltage to 'flicker' as they are locked in this loop. A good solution: gas pulley on the second making it the lead and diesel pulley on the first. This way the voltage comes up on the gas alt first and the diesel one kicks in harder when the gas unit reaches it's limits. That prevents the alts from fighting. Tach off the diesel pulley of course. This is only scratching the surface, but, should point you in the proper direction. FYI 2008 dual alt setups will quit charging if the primary alt fails - as the second unit is only turned on for heavy loads. Solves the fighting each other issue, but, makes zero advantage for reliability...

You only need to tap the power on for the 2nd alternator. Put the remote sense wire in a new run to the main junction or to the load terminal of that 2nd alt. No tap on the tach wire. Reverse the connectors and see if your tach clears up.
 
WarWagon said:
You have to have different size pulleys or some other way to make one alt the lead and the other one the lag alternator. This can be as simple as putting the "remote voltage sense" wire at different locations. Otherwise they can fight each other as one brings up the voltage the other drops off and this oscillates between them. This "fighting" can confuse a regulator and have it shut down the alternator from over-voltage thinking it has failed. One alternator brings the voltage up - what is the second unit going to think if it isn't bringing up the voltage? What if both command higher voltage- the voltage jumps and they both respond with lower voltage causing your voltage to 'flicker' as they are locked in this loop. A good solution: gas pulley on the second making it the lead and diesel pulley on the first. This way the voltage comes up on the gas alt first and the diesel one kicks in harder when the gas unit reaches it's limits. That prevents the alts from fighting. Tach off the diesel pulley of course. This is only scratching the surface, but, should point you in the proper direction. FYI 2008 dual alt setups will quit charging if the primary alt fails - as the second unit is only turned on for heavy loads. Solves the fighting each other issue, but, makes zero advantage for reliability...

You only need to tap the power on for the 2nd alternator. Put the remote sense wire in a new run to the main junction or to the load terminal of that 2nd alt. No tap on the tach wire. Reverse the connectors and see if your tach clears up.
Click to expand...


Thank you. That's kinda what I was thinking. I only have a single wire on the second, my pulleys are matched. I have a smaller pulley I think I can swap on, and still be ok on belt length.

I've got the parts now to do the second alt on my 02 duramax, I am wondering if rather than run that to the computer, I should just tap in to the exisiting like on the dmax to avoid the issue you mention.
 
On my dual setup, one regulator always kicks in first. I put the lower voltage alternator on the right side to drive the Tach. Otherwise, yes the higher voltage regulator will turn off, giving no output for the tach. Each time I replace an alternator, I have to try it, then swap them if the tach drops out.

With using a different Alternator, you may not be able to do that. Does the AD244 have a pulse output? If it does, you could use it to drive the tach. The only issue will be getting the pulley correct for the proper Tach reading.

I haven't noticed fighting or voltage fluctuations. When a heavy load comes on, it back fills. I see this at start up as the glow do the post start after glows. At idle the 100A draw of the glows exceed the output of a single CS133 at idle. With the second CS133, voltage drops to 13.5, not the 10v with the single.

A same with the 200A of my plow pump, if the rpm's are up some (like 1500 or so). Both kick in to maintain a charging voltage.


I would like to get amp meters on each alternator lead to monitor them, but $300 in gauges haven't been in the budget.
 
fastjohnny said:
Now because of my impatience, I have a spare idler pulley and belt, as I had ordered from GM, but got antsy to get it done, and picked up an idler from NAPA and a belt from Autozone. If I get energetic and/or someone really wants dual alts, I might be convinced to make another bracket, and sell with pulley and belt for a kit.

Pics forthcoming.
Click to expand...

Still interested in making a kit? I could use one now. :)
 
You must log in or register to reply here.
Back
Top