hoping some one could help with a problem that is really puzzling me. this past winter i changed from a stock fan set up to a champion radiator and dual electric fans controlled by a switch through fan relay.n everything works like it should except when i turn the fans on the charging system starts overcharging. even if i turn headlights and all acc. on if i leave fans off all is good except car starts to heat up thanks for any input!!! jeff

By over charging do you mean the gauge shows high charge or have you checked the voltage at the battery with the fans on? A heavy draw on the system will cause the alternator to charge at a higher rate.

Or do you mean the ammeter is showing charge because the fans are hooked to the battery?

Like shown here: http://www.heritech.org/cuda/Charge2.html#Problems

If you're OK with the fans running only when the engine is running,have the relays pull the power from the alternator. Then the ammeter will only show what is going to and from the battery. Plus, the fans will be getting power right from the source, instead of going the long way around and through extra connections.

This^

thanks for responses i think im going to run fans directly off alternator, after looking at diagram MAttax posted and the size of factory wire from alternator and how it routes through car seems like good idea to get most of heavier loads(headlights ect ) off of factory wire. even thinking about heavier guage wire from alternator directly to starter relay

Yes could put the relays on a distribution point coming off the alternator. (with regular fuses or breakers).
Then if you want to reduce possible resistance in the power to everything else, run parallel wires as NachoRt did.
This keeps will let you see if the alternator is keeping up with the power demands, especially at low rpm. If it isn't, the ammeter will show the battery discharging.
This way you'll know what is going on, and if the alternator can't keep up, change pulleys or alternator.
After that, if you want to run a parallel charging wire, at least you'll have an idea of what is going on. But there's probably some clever way to relay the fans to run directly off the battery when the engine is off if that's what is wanted. Might want to talk with "Crackedback" Rob about that.

Nacho attached the parallel wires to the respective ammeter studs with ring terminals. This is probably the simplest way as it doesn't involved soldering or adding splices into the main junction.

This sounds way better (I learned something today (& the day is young!). I was thinking that Nacho drilled out the bulkhead halves & ran em straight thru & did it that way.

thanks again i just came in from looking at car trying to figure out best route and actually was thinking a distribution block ,like you said, would be better idea than just one wire back to starter relay. this way i would have a good point to pull off of for headlights and fuel pump. thanks again,jeff

Sure.
The only downside is if there is stuff that will need to run when the engine is off. Lets say for example you needed to run those fans for a 10 minutes after the engine was shut down. In that case the battery will have to send power all the way to the distribution block and through all of the connections in between. If its only a couple of amps, it doesn't seem like a big deal. But when the engine is started, the battery will be low and charging will be high flow for at a few minutes. So that's when we have to be careful.

For example a few years ago I accidently left the parking lights on all day in my '67. After jump starting, the battery was taking all the power it could. At idle, the alternator can only supply like 10 amps. But as soon as I started driving, it was able to supply 20 - 30 amps. So what I had to do was turn the lights on, and shift it into neutral and coast wherever possible. This kept the battery from sucking so much power.

I only drove it about 20-30 minutes to get back to base camp. The battery was hot. Batteries don't actually charge well when hot, but they don't know that so they suck all the current they can when low. Next morning it was cool, but not fully recharged. We had no charger in camp. So, did the same thing on the first leg out of camp - about 30 minutes. By then it was starting to get close to fully charged. Let it charge at idle for a bit more, and then it was pretty much back to normal for the rest of the trip home.

So anyway, this is a situation that can occur anytime the battery gets drained.

But depending on the situation, sometimes it does make sense to have a direct wire from the battery to the alternator. That's when a voltmeter makes sense because its a different wiring strategy.

Nacho's situation was such that simply raising the idle speed a little and using a better alternator would keep the alternator as the highest voltage source. But all he needed to do was keep the battery from discharging when running the A/C at idle (sitting in traffic).