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Alternator Wire Size??

36K views 25 replies 8 participants last post by  nolimitpkr 
#1 ·
#2 ·
this is a partial chart from chevellestuff.com
Recommended Charging-Cable Gauge Size

AMPS To 4-ft 4-7 ft 7-10 ft 10-13 ft 13-16 ft
85-105 6 6 4 2 2
105-125 4 4 4 2 2
125-150 2 2 2 2 0

factory charge wire is only 10-guage, if your going to upgrade to this kind of set-up you should research the tech reference series on the tech tab above, and or visit the mad electrical site, ot the chevellestuff.com site, all have a lot of info on swapping altenators and wiring correctly to prevent overheating (fire) wires. i rewired the front of my car with the recommendations of the MADelectrical site and it works great like it should.....:)
 
#3 ·
Vince thanks, I have been reading through some of that stuff, very informative. I am very inexperienced when it comes to wiring, so some of the stuff is over my head right now. The only power accessory I run is the fan, no ac or stereo.

If I run a 2 gauge wire, does it need to be just from the alternator to the horn relay, or all the way to the battery?? Thanks for your help...
 
#10 ·
Thanks for the help guys, I just have a mental block with wiring... This project could be beyond my knowledge, I guess I will just have to start tearing stuff apart and find out where it goes.

Does the main alternator power wire go to a splice before going to the horn relay??

I think I understand that the main wire will need to be upgraded to the horn relay(2 gauge), but no need to upgrade from the wire from the horn relay to the battery, is this correct??

Sorry if I am repeating myself, I just have trouble visualizing this type of stuff. I never understood Algebra until someone showed me step by step what to do, so thanks for your patience...
 
#11 ·
I've got a CS-130 alternator in my '69. I put in dual 8 ga wires from the alt. to the distribution point. You don't need a system to handle 140 A. You should size the wire for the load required. You will normally only be using a fraction of that current. If you are actually going to be continuously drawing 140 A then you need an even bigger alternator.
 
#12 ·
I've got a CS-130 alternator in my '69. I put in dual 8 ga wires from the alt. to the distribution point. You don't need a system to handle 140 A. You should size the wire for the load required. You will normally only be using a fraction of that current. If you are actually going to be drawing 140 A then you need an even bigger alternator.
I am thinking of going to the 140 because the 100 amper I have now is only showing 13.20-13.60 volts when the fan is running and the car is idling. Is that enough volts to keep the battery charged? The system is on my bracket racing car and the last thing I want is to have a dead battery in the staging lanes...

Also can an external regulator handle the current load from my 100 amp alternator??

Thanks guys, TC ROCKS!!!!!!!!!!!
 
#17 ·
I need some help, I moved the power wire for the fan relay from the battery to the horn relay. At idle when i check the volts at the battery I now have 14.30-14.40, steady, instead of 13.30-13.60 when it was connected to the battery.

The car will not start after I let is run a while or go around the block a couple of times. I always check the voltage and even when I pull in the garage after a ride, it still shows 14.30-14.40 at the battery at idle. When I turn the car off I still have 12.50-12.60 at the battery.

Could the battery just be too weak to begin with, it only has 600 something cranking amps??

Why is the battery not charging, do I just need to give up on my old set up, and convert to an internally regulated CS130 type alternator, and run the 8 gauge wire, ect, ect??
THanks...
 
#21 ·
The car will not start after I let is run a while or go around the block a couple of times. I always check the voltage and even when I pull in the garage after a ride, it still shows 14.30-14.40 at the battery at idle. When I turn the car off I still have 12.50-12.60 at the battery.
Recheck the battery connections. If it had always started before, the problem is probably there as it was the last thing that was touched.
 
#18 ·
The higher voltage at the battery is because you're not drawing as much current through the wire from the horn relay to battery. That was causing a voltage drop, lower voltage at the battery. You've got a reasonable charge voltage at the bat now, over 14v, and a good charge on the battery, over 12v. You don't need a new alt to solve you're starting problem.

You might have the common heat soak problem. The starter heats up from engine heat and won't start until it's cooled down. Make certain the connections on the starter are good and tight and clean. Also the connections at the battery and main ground wire to engine. May not solve the problem but it's a start. Any corrosion of the cables at the ends and they should be replaced. Do a search of this forum for 'heat soak', should come up with lot's of reading material if you want to know more.
 
#19 ·
Thanks for the response Hank. I was thinking about heat soak, but the thing is I had ran the car for about 3 years with no problems, until I added the fan, but I will for sure check the grounds and connections. BRIAN....
 
#23 ·
No I have a manual switch inside the car, that controls the relay. I always start the car with the fan off and kill the fan a second or two before killing the motor.

Check the battery to starter connection and the connection on the 'S' terminal of the starter as well. When the fans where hooked to the battery were they hooked directly to the battery or the junction block. Check the connection at the junction block and the horn relay as well. Any bad connection in the positive circuit can drop the voltage going to the starter. When it's hot it requires more current and a bad connection can keep it from starting. A marginal connection, positive or ground, may not show up when the car is running or cold but a hot starter requires a lot of current.
Sorry but where is the junction block and whats it's function?? Thanks...

Recheck the battery connections. If it had always started before, the problem is probably there as it was the last thing that was touched.
Will be checking, cleaning, or maybe replacing battery cables, grounds, ect over the enxt couple of days...
 
#25 ·
While you're at it. If your battery ground cable is connected to the head or the alternator bracket, move it directly to the engine block. The boss in front of the engine by the fuel pump is a good location. At any rate make sure the bolt threads attaching the cable are clean and put an internal star lock washer before and after the cable lug. The star washers will bite into the metal and help provide a lasting electrical connection. "Heat Soak" start problems are sometimes traced back to "iffy" battery ground connections. Let us know what you find.
 
#26 ·
:):):):)

Ok I figured it out, I think. Connected the main ground for the battery directly to the block, cleaned and repaired all connections and WOW no starting problems. I ran the car for about 30 minutes got it nice and hot, and she started right back up.

Thanks everyone for the all the help.
 
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