Please give me some educated answers

[holley2346 6]

Okay so I ordered and installed the dual alternator kit on my 2008 tahoe. The install only took about 2 hours which wasn't bad. ***THERE WERE NO INSTRUCTIONS PROVIDED WITH THE KIT ANYWHERE*** I did call the number and got some limited assistance. The person I talked to, Stan helped the best he could but gave me no 100% sure answers... so I'm left with some questions.

Please keep in mind this is a 2008 tahoe with 2 prong OEM alt connectors

First let me tell you how I installed it;

(1) I ran the red wire with a ring terminal on the harness provided from DC to the positive output on the alt

(2) I ran the white wire with a ring terminal on the harness provided from DC to a ground source

(3) I ran the red wire with no end on it to a fuse that is only on when the truck is on (as instructed by Stan)

(4) I ran the power wire from the DC alt to my stock battery (which is connected to my bank in the back)

When I had it set up this way there was A LOT of load on the alt and it got warm pretty quick, so I disconnected the harness and called Stan. He notified me that the 2 alts HAD to be connected to separate battery banks... so I connected the DC alt to my bank in the back. After doing this there was less load on the DC alt, but the alt was only charging around 14 volts and was down to 13.x (just running a sundown 50.4 wide open).

So after all this I'm left with lots of questions....

(1) Why is the DC alt letting my bank in the back go down to 13.x volts when it's just running my 50.4 (I have no subs at the moment)

(2) Did I do the right thing in running the red wire with nothing on it to a 12v switched source (as Stan instructed)?

(3) I want to have both alts charging everything, not separate banks... I would've just ordered a single alt if I only wanted to use one. So what do I need to do this?!?!?

(4) What does the harness do exactly that came with the DC alt... I was assuming it was some sort of a regulator, if it is what voltage is it set to?

(5) I will get the XS power VCM if I have to, but would like to know a cheap simple way for both alts to be controlled by my stock ECM (which is how the OEM one works).

(6) My alternator whine through the speakers used to be tolerable, but now it's horrible!

(7) Online it says that they use the same size pulley on DC alts as the OEM uses, but the DC alt has a MUCH smaller pulley.... almost half the size?!?

I know a lot of questions..... I'm really good with the electrical field.... I just thought I had it all figured out, and ended up with tons of questions.

Thank you so much

By the way, props to DC for at least answering the phone and providing a complete kit quickly.... if only it had instructions.

The main question I need an answer to is this;

**How do I get both alternators controlled by the same system (preferably the stock ECM) so that I can have all my batteries and all my alts hooked up together as one system.

Edited November 18, 2010 by holley2346

[DC Power Rob 4]

Okay so I ordered and installed the dual alternator kit on my 2008 tahoe. The install only took about 2 hours which wasn't bad. ***THERE WERE NO INSTRUCTIONS PROVIDED WITH THE KIT ANYWHERE*** I did call the number and got some limited assistance. The person I talked to, Stan helped the best he could but gave me no 100% sure answers... so I'm left with some questions.

Please keep in mind this is a 2008 tahoe with 2 prong OEM alt connectors

First let me tell you how I installed it;

(1) I ran the red wire with a ring terminal on the harness provided from DC to the positive output on the alt (Correct)

(2) I ran the white wire with a ring terminal on the harness provided from DC to a ground source (Correct)

(3) I ran the red wire with no end on it to a fuse that is only on when the truck is on (as instructed by Stan) (Correct again)

(4) I ran the power wire from the DC alt to my stock battery (which is connected to my bank in the back) ((Usually Correct, see below))

When I had it set up this way there was A LOT of load on the alt and it got warm pretty quick, so I disconnected the harness and called Stan. He notified me that the 2 alts HAD to be connected to separate battery banks... so I connected the DC alt to my bank in the back. After doing this there was less load on the DC alt, but the alt was only charging around 14 volts and was down to 13.x (just running a sundown 50.4 wide open).

On *your* vehicle, as well as all GM vehicles with RVC (2 pin plugs) the PCM controls at what voltage setpoint the alternator charges at, regardless of what current is being produced. Because your stock alternator was being told to charge at x.xx voltage, and our alternator was charging higher than that point, your stock alternator was just doing it's job and essentially shut off. It saw voltage higher than what it's charging algorithm said it should be, so therefore it saw no need to charge because as it sees things, everything is perfect. (RVC is a funny thing, and I could talk for an hour explaining it, and it would take me 3 hours to type it out) Your interpretation of temperature is kind of correct.. It was correct, because your secondary alternator just became the primary alternator and is being worked a little, and therefore getting "warm", but not so correct because what you see as "warm", isn't even warmed up. With that said though, alternators aren't really "warm" until they leave insta blisters when you touch them..

So after all this I'm left with lots of questions....

(1) Why is the DC alt letting my bank in the back go down to 13.x volts when it's just running my 50.4 (I have no subs at the moment) What kind of batteries, how far is the run to the back, and how well is it wired?

(2) Did I do the right thing in running the red wire with nothing on it to a 12v switched source (as Stan instructed)? Absolutely..

(3) I want to have both alts charging everything, not separate banks... I would've just ordered a single alt if I only wanted to use one. So what do I need to do this?!?!? On your vehicle, SOLELY because of the RVC, it's almost impossible because the alternators run separate voltages. The stock alternator will always be the "slave" and the secondary will always be the "primary" alternator. Thank the engineers at GM for this one..

(4) What does the harness do exactly that came with the DC alt... I was assuming it was some sort of a regulator, if it is what voltage is it set to? The harness's sole purpose is to excite the alternator. Voltage setpoint on those alternators is generally 14.8 @ ambient air and they will temp compensate down to 14.2 or so generally.

(5) I will get the XS power VCM if I have to, but would like to know a cheap simple way for both alts to be controlled by my stock ECM (which is how the OEM one works). This is almost impossible, at least if you want good voltage, solely because of your PCM, and something on ALL GM vehicles with RVC. A VCM will do you absolutely NO good on your vehicle because they don't make one that works with the PCM.

(6) My alternator whine through the speakers used to be tolerable, but now it's horrible! If you had whine with your stock alternator, your picking up noise that's install related, almost a certainty there. 99.9% of the time noise is either wires too close that shouldn't be, or ground loops.. It shouldn't have gotten worse because the alternator you got is one of the cleanest there is on the o-scope. 99.999% sure you got a 250SP upgrade on the house..

(7) Online it says that they use the same size pulley on DC alts as the OEM uses, but the DC alt has a MUCH smaller pulley.... almost half the size?!? On XP's we run mostly stock diameters, on the SP's we run smaller pulleys, I'll have Kyle update the info on the website. As a *general rule* though, we run small pulleys on GM dual kits as there is no downside to it.. Your vehicle has a larger than normal pulley (2.44") which makes it seem MUCH smaller than it is..

I know a lot of questions..... I'm really good with the electrical field.... I just thought I had it all figured out, and ended up with tons of questions.

Thank you so much

By the way, props to DC for at least answering the phone and providing a complete kit quickly.... if only it had instructions. Unfortunately, I cant find our E-copy, and we're out of printed copies, and we just haven't had a vehicle in to reshoot pics and re-do instructions.. My apologies for that one..

The main question I need an answer to is this;

**How do I get both alternators controlled by the same system (preferably the stock ECM) so that I can have all my batteries and all my alts hooked up together as one system.

I answered this above, but unfortunately, as controlled by your vehicle, it's just not really feasible, at least easily.. You can run an MLA module, but that's just an added expense. I wish it wasnt the case on late model GM's, but we have to work with what the vehicle manufacturers do with their electrical systems, and unfortunately sometimes they just plain aren't friendly to what you or we would like to do with them..

[holley2346 6]

I really appreciate all of your knowledgable replies.... it is VERY appreciated. I am by no means knocking DC Power in any way, so far I love my alt and over all I love the support you provide your customers. So now comes the challenge... getting both alts to put out the same voltage so I can run everything together. I can fix the whine issue, I believe it's in the path my RCA's are run. The 13.x voltage issue wasn't aparent today (it was charging around 15.0 for the first hour it ran).

If it's impossible to run a VCM then can I get a 4 wire plug alternator from ya'll? Then both alts will be the same type and I CAN run a vcm.... If I do this will my ECM start throwing error codes?

If the MLA module will allow me to run everything together... and save me the expense of buying a 4 wire alt to replace the stocker + the vcm I'll do it.... but will this throw error codes? And can I get one that will hold the alts at ~14.9? I have no need to change the charging voltage on the fly, as long as I get a steady 14.9 I'll be happy.

Thanks!

Edit: I just thought of this... but could I just connect everything and run it as is? My stocker will be shut off and the DC alt will be running everything until I put a heavy load on the system, then my stocker will kick in and add the needed amperage.... Just a thought.

Edited November 18, 2010 by holley2346