My alternator recently went out and I decided to upgrade to a summit racing chrome 100 amp. And it has been a nightmare. I will spare you all the fitment issues.....my issue is wiring. There is a 10 ga wire wired in to the main battery wire, and it leads to a junction point. The 10 ga wire from the alternator leads somewhere....it appears to run through the firewall.

I thought I would upgrade to an 8 ga wire and directly to the alternator. The car started and ran great, it was charging fine (I made sure the battery was over 12 volts before I started the car), but after shutting it down and messing around in my yard for a few hours, I noticed the alternator was very hot! I immediately disconnected the battery and let it cool down.

I had to drill out the lower bolt hole in the alternator so the stock lower bracket bolt would fit. it bolts to the head, and the head is aluminum. so I dont know if perhaps I am not getting a good ground. The original alternator seemed to be grounded fine (it was a 63 amp....at least that is what google told me).

The car has a summit racing ignitition system, and the alternator is internally regulated, as was the old one. I don't know the following:

What it is heating up and drawing the battery down when the car is turned off.

if a 100 amp alternator will work with the 10 ga wiring already in place. I think the answer is probably no.

can I wire the alternator directly to the alternator, and if so, do I disconnect the 10 ga wire coming off the main battery cable that seems to go to that junction point?

Why is the alternator drawing current? is there something I am bypassing by going driectly from the alternator to the battery that would cause this?

And to top it off....my GF put the garage door down while I was working on the car...and it caught the spoiler. Good times.

 

Did you buy a one wire alternator? If so, then you don't use the wire that was attached to the old alternator. You tape that one up, and run one new wire straight from the alternator to the battery. And you lost me on "can I wire the alternator directly to the alternator"

 

it is a "one wire capable" alternator, but I am using the 2 wire connector....because it is there, and I am not sure how to work around it. Again, I am trying to figure out why it is getting so hot and drawing down the battery with the car off.

 

Also, my question about "can I wire it straight to the alternator"....let me clarify. I know I can. I already did. But....am i bypassing something the may be causing the heating and draw issue by doing so. As I described in my post, the old alternator is not wired directly to the battery....it heads off into the firewall, while the wire coming off the battery leads to a junction point in the nose of the car. Thank you for your help!

 

Since your car didn't come with an internally regulated alternator from the factory, you're at the mercy of how the previous owner rewired it. Is it connected to something that would cause a draw? Maybe. You don't need to run through the firewall to tap into the main supply wire, which is in the engine compartment. Also, you don't want to hook up both the 2-wire way in addition to hooking up straight to the battery the one wire way. That defeats the purpose of a 2-wire charging system. The third wire, if the guy used it, is for the idiot light. Decide which way you want it hooked up, don't double up the connections. But having both connected wouldn't cause a power draw, unless previous owner wired it wrong. The other possibility is a bad alternator. The diodes act as an electrical check valve, if one is bad, you'll get a current draw and drain the battery. After you shut the engine off, put your ear to the alternator. Can you hear a slight whistle or whine noise? If so, alternator is bad.

 

thanks for the reply! I didn't notice a strange sound or anything like that. It seemed fine. To your point, I have no idea how the car is wired. It would appear to be ok loosely based on the outdated diagram in my book. Let me ask this...After doing some research, would it be your opinion that running directly to the battery from the alternator is causing the heating and battery draw? it would seem to me to be pretty logical, given there is nothing to interrupt the constant flow of current. If that is the case, I have read that the right thing to do is to run the 8 ga to the starter solenoid with a fusible link in between. Now if that sounds right, the original 10 ga coming off the positive battery cable that goes to that junction point.....is that now out of play? in other words, if that wire goes to an ignition on source, but now wiring to the solenoid provides that "on" signal for the alternator, can I get rid of that wire? or would it affect the two pin connector?

 

No, wiring the alternator direct to the battery won't cause a battery draw, unless the alternator is bad internally. With a conventional charging system, the hot output wire from the alternator goes to the battery, and is live all the time. The voltage regulator exciter wire at the alternator connects to that same wire, but is further upstream where it can monitor current draw and demand from components that are using power, and will activate the regulator accordingly as needed. I'm not totally following you on the other point, not knowing how your car has been rewired, if it has?

 

I sure appreciate the help. Just to clarify your last question a bit...I don't know the history of the car...under the dash and around the engine bay the wiring appears to be stock, with the exception of the different things that have been added (ignition, etc.). So let me step back for a second...This all started with a bad alternator, and my decision to upgrade to a stronger alternator and a thicker power wire. if I had simply dropped the new alternator in, I would assume that would be a problem because of the 10 ga power wire. So I guess if I break it down, either my new alternator is bad, or my power source is incorrect, or both. How would you have run a new thicker power wire? directly to the battery, or to the starter solenoid? or neither? I am considering scrapping this for now and going back to a new version of the alternator I pulled off, and then figure it out later. At least the car would work. This is very frustrating. One note...the other alternator seemed to fail after a hard acceleration...got the dummy light, my voltmeter dropped, etc.....I don't know if that could have finally killed it or if it was a coincidence. Based on the sku on the alternator, it was a rebuilt alt from O'reilly's....

 

quick update.....I decided to go to ground zero and start over with a new alternator....same one I had originally, so I could keep the 10 ga power wire in place and take any wiring I did out of the equation. I hooked it all up, added a ground wire to the new alternator, started the car, and noticed the console voltmeter gauge was under 14. I turned the key off....and the GEN light in the dash stayed on! Good Lord. I put a voltmeter on the battery and it was 13.50 and dropping. I disconnected the battery and have checked it a few times. it is holding charge. why would the GEN light stay on? What switch, relay, etc. would be in that path that is not interrupting the current to the light? A friend told me to start with the sensing wire...clip that and see if it changes. If it does, then what? Do I seem a little lost? I am.

 

Try wiring the alternator the old school one wire way. Jumper the exciter wire from the plug (the right side wire when looking at the back of the alternator) directly to the hot lead on the alternator. Then run a wire from the hot lead to the battery. You can leave the idiot light wire (left wire on plug) connected, that acts as a momentary diode to prevent the alternator feeding back power and making the engine run on when you shut off the ignition. If that works, and it should, then something is wired wrong with your existing setup.