starter and alternator hookup

Here is one question that I stumbled over last time. i have some wire from a 220 welder, 2 gauge or one gauge. Last time I ran a separate wire to the alternator and starter individually. What I was wondering is if I could hook the wire to the starter and then to the alternator or vice verse instead of having two heavy wireds running through the bay.

No. I wouldnt try that. One is feeding to the battery and the other is feeding from the battery. Two different directions. Once you turn the key, you are effectively back feeding the alternator....this will fry the alternator in short time.

They both need an isolated circuit.

Ok I was making sure before I hook it up all wrong, just trying to lose some wire weight, this stuff is heavy.

Yeah, I understand. But, proper wiring isnt the place to start cutting weight. Wiring can make or break your conversions reliability. I say go the extra mile in wiring!

roger that.

I know this is old but I thought I should make mention that there is no problem with wiring them the way he asked about. Porsche had it wired like that originally. It is the same either way except the one way has more weight as stated.

I was thinking it might work because on some vehicles the battery is in the fender and have power blocks in the bay that the wires hook to.

Also even thinking about that. How does the wire to the starter differ from the alternator if they both hook to the positive terminal?

There is no difference between them. They are both at battery voltage.

There is no difference as mathewb stated. It needs to be a heavy wire because the starter can draw a huge amount of current. I use a minimum of 4 ga. wire. You need bigger (2 or 0) if you remote mount the battery.

I know about the heavy wire, The stuff I am using is a 2 gauge wire from a 220 mig welder that a shop gave me about 25 ft of during my first setup. Alot of strands in it to help with the amperage. The reason I did not have it originally in the truck was due to now knowing how to connect two pieces of that together.

if the starter draws alot of amperage and the Alternator hooks to the same wire, how do would you go about making a connection in a wire setup like that?

They make terminals for that size wire. They also make a swaging tool for these terminals . You put the terminal on the wire and into the tool and hit it with a hammer. There is one like the one I have here

http://cgi.ebay.com/Hammer-On-Welding-Cable-Lug-Crimper-NEW-LENCO-840_W0QQitemZ160514600253QQcategoryZ11774QQcmdZViewItem

I would make up two wires and connect the two together at the starter just like your drawing.

I already have that, what I am asking is, do I just screw two copper terminals together at the starter or try and fit both wires into one terminal at the starter ans have the other end to the altenator?

This one again!
I really didnt think all this was gonna be necessary as I thought it was just a quick question. Didnt want to dilute it with theory.
The problem is not that you cant wire it like that because, yeah, you can. But, the LS starter, as well as all starters, has been known to give off an AC current/spike that fries the alternator when wired in series. The way you are telling him to wire it, theres no fusible link, no way to discharge the spike, and no protection for the alternator in the event of starter failures as there is on a stock LS harness/route that can absorb the types of spikes or alt bleed offs. As well, if the current load on this circuit is ever disrupted while running, the alternator will reference 0.

Stock LS cars have the alternator and starter wired in parallel not in series. One reason is to be able to get rid of alternator bleed off and exclude the alternator from any starter failures or activities such as AC spikes. Another reason GM does it this way is the fact that two loads wired in parallel draw less than two wired in series (Ohms law).

The flaw in your reasoning is first, the alternator is not "draw" current, it generates. It is not generating during starting so it doesn't add to the current flow of the starter. Secondly, unless there is a diode in the circuit or some device to keep spikes from the alternator, it doesn't matter where you connect the wires the alternator will still see the spikes. How would a starter generate an A/C current spike anyway? It is a D/C motor and even if it was turning with the engine it could only generate D/C. Also, alternator bleed off will still happen with the two wired in series again given no other additional component to eliminate it.

There shouldn't be any alternator bleed off anyway or your diodes in your alternator are bad. This would not change no matter how you wire it. The sense wire is what would cause bleed off if not wired correctly which is through the ign switch. If this wire is connected to B+ you would have a constant draw from the alternator even with the ign switch turned off. The alternator will not charge without this wire.

As far as a fusable link it would need to be between the starter and the alternator.

Yeah, going to have to agree with V8 on this. Porsche actually still wires there cars this way... I also agree with the fact that it doesnt matter where you connect the items to the B+ system, if there is a spike the entire system will see the spike, your battery actually acts like a buffer for some minor noise, that is one reason you arent supposed to disconnect your battery while the car is running. And there are two sources in this situation, not 2 loads.

Mark

I reused all of the stock porsche battery and alt to starter wiring on my LT1...it's wired in series with one wire coming from positive to starter, then one going from starter to alternator, never had any problems with killing starters or alternators (except for the mexican cast crap alternator that i had that had the aluminum housing break in two!)

I understand theres two ways and understand that porsche wires them like that. GM doesnt and he is using GMs stuff. Starters have been shown to give off AC spikes...thats already been proven. You can research that one.

Basically, we were working on the best method of wiring them and with me having the thought of the starter going bad eventually and any other problems that could arise. Running them in parallel is the best method in this case. If you want to argue that, email the GM engineers.

I'm not trying to tell you that you're wrong or anything...you're one of the most knowledgeable guys on this forum no doubt. What i don't understand is how there is such a big difference between a porsche starter and a gm starter...other than the obvious stuff, they both do pretty much the same thing the same way right? Now my other question is if GM took into consideration these AC spikes, why wouldn't Porsche? Is there some massive difference in how the GM and Porsche starters and alternators function, or is it just a case of different strokes for different folks?

I will say that the Porsche Starter and alternator are much higher quality units. I have never seen a Porsche starter fail electrically, and only a handful of the alternators. Now GM on the other hand... But to put this into perspective, if you told a guy driving even a Corvette that his alternator failed and its $1200 to replace I dont think that would go over to well...

Mark

I will say that the Porsche Starter and alternator are much higher quality units. I have never seen a Porsche starter fail electrically, and only a handful of the alternators. Now GM on the other hand... But to put this into perspective, if you told a guy driving even a Corvette that his alternator failed and its $1200 to replace I dont think that would go over to well...

Mark

I've had both fail. Both Porsche parts. Not saying that they're not better quality than the GM parts, just that they do fail too.

"I've had both fail. Both Porsche parts. Not saying that they're not better quality than the GM parts, just that they do fail too." I apologize for not pointing out the fact i was talking about current (last 13 years) of Porsche's, as that is what i work on every day. I have had a starter on my 944 die also not much different on those old ones.

Mark


Ok, I had to do a little digging on this... It was bugging me, cause i really dont see the logic behind changing the wiring to save the alternator. Here are wiring diagrams for a C5 and C6 Vette, i believe the top one is a C5 and is wired exactly as i am wiring my GM starter and alternator, and the bottom is the C6 and just runs a wire from the battery to the alternator and pulls off that line for the starter. And now that i think about it thats how the trucks are wired also, there is a line coming off the positive battery post that goes about a foot and there is a T that splits for the starter and alternator, I just dont see that shielding the alternator from any AC voltage, and i dont understand how AC voltage would hurt the alternator anyway. Not looking to start a pissing match, just trying to give someone good honest advice.

Mark

I apologize for not pointing out the fact i was talking about current (last 13 years) of Porsche's, as that is what i work on every day. I have had a starter on my 944 die also not much different on those old ones.

Ahh, yes that would make a difference.

Marky522 wrote: just trying to give someone good honest advice.

Well.... thats a bit offensive. But thats okay, I know what your trying to say But, what do you think I was doing!?!?! That was good honest advice!

Ya know, I believe this is why we just dont have a whole bunch of guys posting answers to questions here. I think they just dont because of the thought of having to prove themselves afterwards...why deal with all the hassle? Just let someone else do it. What amazes me is that after the post is done, thats when people start chiming in....

Well, I dont mind proving myself. Its not like Im making this stuff up as I go. What were arguing over is two ways to skin a cat. Its like we have nothing more to do! Neither of the methods are wrong...its just GM decided to stop wiring them that way...and when they do something like this, its usually for a damn good reason that alot just dont understand. I was curious when I wired up my LS3 and found a crap load of info. So, thats what I posted.

Regardless, I KNEW that my porsche had the starter and alternator wired in series originally....20+ years ago....when I originally posted. However, I also know that it was 20+ YEARS AGO and that he was using LS equipment the same as me. Now, my engine is a 2009 engine....his is not. But, I made the conscious decision to make my post from information from my 2009 manual to help him out INSTEAD of using the manual for my porsche made 20+ YEARS AGO. I could have posted info from the 60's of how British car electronics were done too but I decided to give him the most current info I had....giving him "good honest current advice."

So....... cfgioja, if you wish, you may remove the extra wire that I told you to install to replicate what my manual says and wire them in series to save the weight. I dont mind.

Here are the schematics scaned directly from my 2009 Factory Service Manual (not Haynes, not Chiltons, not from the internet).



As far as why GM did this, I cant re-find the information nor do I think I have to; they had their reasons and you guys can do it the way you want.

First, thank you for understanding what I meant by just wanting to give a complete answer. Second, your post was kind of funny, because after I spent the time looking for those corvette diagrams I made that exact comment to my wife "This is why I just lurk, most of the time the time people will take the advice of the person with the higher post count (Rennlist is HORRIBLE for this).

Regarding using a 20 year old setup, when I wrote that I wasn't basing it on the fact that Porsche originally wired it that way, your correct that was 20+ years ago, I was going off the fact they STILL do, and even if Porsche uses a higher quality starter / alternator they still do the same thing. I'm NOT saying your setup is wrong, just as I don't think your saying mine is, it really would be unrealistic for me to run a second line all the way to the battery in the rear. Honestly he can wire it either way and be fine, now I am going to try and find the info on this AC voltage stuff cause you have me interested!!

Have a good one,
Mark