Alternator question ???

Johnny Rod · 09-03-2016, 01:28 PM

What amp alternator do you recommend I run. Dual electric fans ,fuel pump, water pump, and MSD 6al. Also should I run the charging wire all the way to the back to the battery or to the hot side of the starter relay upfront ?

Greenlight · 09-03-2016, 10:59 PM

Add up the amp draw from each component and run an alternator at least of that amp rating.

Ex:
2 fans at 15 amps each
1 water pump at 20 amps
1 fuel pump at 12 amps
1 MSD box at 1 amp/1000 rpm (~8 amps?)
Other misc. 5 amps

Total amp draw = 75 amps

The wire from the alternator should be large enough to handle the amp load for the distance the wire is run AND the ground system should also handle the amp load.

Johnny Rod · 09-03-2016, 11:13 PM

Thank you !!!!!

Eman · 09-04-2016, 10:46 AM

If you run the alt wire to the starter relay at the frt. the car might not shut off as the alt will keep the system powered even with the switch at the back turned off. That's assuming your battery is in the back and you have a master shutoff at the back. The best way to wire it is to use a master shutoff that has 4 posts. One set of contacts shuts the main battery cable and the other set shuts the power from the alt. If you do it this way you have to run a heavy enough cable from the alt back to the switch. If you wire the alt directly to the battery it will solve the run on problem but the alt wire will stay hot all of the time. I've had the alt. go bad and drain my battery down when parked wired like this.

cmracing · 09-04-2016, 04:25 PM

You can also use the second set of small terminals on the battery cutoff switch to kill the points input to your MSD unit (if using one). When that wire is kept grounded all the time, no spark, no spark, no run. This lets you kill ALL the power in the car and have nothing hot when the switch is off.

If this is a Stocker you have a live battery up front, that is a different story. I have wired them and had to use a secondary continuous duty relay to kill that second battery.

FireSale · 09-04-2016, 09:23 PM

I had a lot of difficulty with alternators in my street/strip Mustang. I switched to a one wire from East Coast Auto Electric and installed/wired it by their instructions and it did the trick. Tossed the wire to the starter relay and ran it directly to the battery in the trunk. Used a Moroso 4 pole cutoff switch and it kills everything.

Wire gauge is based on two things: amps carried and length. There are charts online.

Link: https://www.tessco.com/yts/industry/...get_wired.html

I used 4 gauge to run from the trunk of my Mustang to the alternator. It was the best I could do.

NAPA has bulk auto wire in battery sizes.

Dale

Johnny Rod · 09-06-2016, 05:56 PM

Thanks for all the info it's been helpful. When I doubt ask class Racer 👍🏻

09-03-2016, 01:28 PM	#1
Johnny Rod Junior Member Join Date: Aug 2006 Location: Great River LI N.Y Posts: 90 Likes: 0 Liked 0 Times in 0 Posts	Alternator question ??? What amp alternator do you recommend I run. Dual electric fans ,fuel pump, water pump, and MSD 6al. Also should I run the charging wire all the way to the back to the battery or to the hot side of the starter relay upfront ?

09-03-2016, 10:59 PM	#2
Greenlight Member Join Date: Dec 2004 Posts: 208 Likes: 9 Liked 70 Times in 18 Posts	Re: Alternator question ??? Add up the amp draw from each component and run an alternator at least of that amp rating. Ex: 2 fans at 15 amps each 1 water pump at 20 amps 1 fuel pump at 12 amps 1 MSD box at 1 amp/1000 rpm (~8 amps?) Other misc. 5 amps Total amp draw = 75 amps The wire from the alternator should be large enough to handle the amp load for the distance the wire is run AND the ground system should also handle the amp load.

09-03-2016, 11:13 PM	#3
Johnny Rod Junior Member Join Date: Aug 2006 Location: Great River LI N.Y Posts: 90 Likes: 0 Liked 0 Times in 0 Posts	Re: Alternator question ??? Thank you !!!!!

09-04-2016, 10:46 AM	#4
Eman Member Join Date: May 2014 Location: E TN Posts: 441 Likes: 14 Liked 105 Times in 60 Posts	Re: Alternator question ??? If you run the alt wire to the starter relay at the frt. the car might not shut off as the alt will keep the system powered even with the switch at the back turned off. That's assuming your battery is in the back and you have a master shutoff at the back. The best way to wire it is to use a master shutoff that has 4 posts. One set of contacts shuts the main battery cable and the other set shuts the power from the alt. If you do it this way you have to run a heavy enough cable from the alt back to the switch. If you wire the alt directly to the battery it will solve the run on problem but the alt wire will stay hot all of the time. I've had the alt. go bad and drain my battery down when parked wired like this.

09-04-2016, 04:25 PM	#5
cmracing Member Join Date: Aug 2016 Posts: 173 Likes: 113 Liked 62 Times in 29 Posts	Re: Alternator question ??? You can also use the second set of small terminals on the battery cutoff switch to kill the points input to your MSD unit (if using one). When that wire is kept grounded all the time, no spark, no spark, no run. This lets you kill ALL the power in the car and have nothing hot when the switch is off. If this is a Stocker you have a live battery up front, that is a different story. I have wired them and had to use a secondary continuous duty relay to kill that second battery.

09-04-2016, 09:23 PM	#6
FireSale VIP Member Join Date: Feb 2014 Location: Lakewood Washington Posts: 1,407 Likes: 29 Liked 236 Times in 127 Posts	Re: Alternator question ??? I had a lot of difficulty with alternators in my street/strip Mustang. I switched to a one wire from East Coast Auto Electric and installed/wired it by their instructions and it did the trick. Tossed the wire to the starter relay and ran it directly to the battery in the trunk. Used a Moroso 4 pole cutoff switch and it kills everything. Wire gauge is based on two things: amps carried and length. There are charts online. Link: https://www.tessco.com/yts/industry/...get_wired.html I used 4 gauge to run from the trunk of my Mustang to the alternator. It was the best I could do. NAPA has bulk auto wire in battery sizes. Dale __________________ Dale Shearon 68 Mustang 6394 Last edited by FireSale; 09-04-2016 at 09:25 PM.

09-06-2016, 05:56 PM	#7
Johnny Rod Junior Member Join Date: Aug 2006 Location: Great River LI N.Y Posts: 90 Likes: 0 Liked 0 Times in 0 Posts	Re: Alternator question ??? Thanks for all the info it's been helpful. When I doubt ask class Racer 👍🏻