After reading a few posts about alternators and charging I began to wonder about something.

Two years ago I installed Spal fans, a 110 amp Powerhouse alternator and replaced the amp gauge with a volt gauge. I spliced the amp gauge wire together. In city traffic when the fans come on, the volt gauge has at times dropped to near 12v, but then after a bit of cruising it will climb back to 14+.

The hot wire off the alternator appears to be a #10 routed as the factory did with the exception I wrote above.

Would it be wise to replace this wire with a #8 or #6, or maybe to route an additional #10 from the alternator directly to the starter batt terminal?

 

Whay you really want to do is take the main fan power right off the alternator frame/case ground and main power stud directly....with fuse of course...leave the rest of the crap alone, it's fine...

GENE

 

When I installed my new Painless harness it had a seperate wire to run to the starter solenoid for alternators over 65 amps (maybe it was 80 amps).

ltlevil

 

The optimum wiring setup would have the two Spal fans source pwr wired as close if not directly to the Battery positive terminal as possible. This would provide the lowest source impedance to the inductive fan motors resulting in the minimum chance of producing inductive voltage spikes into the electrical system. Having said that, the Vette wiring provides source/charging current from the alt. via the horn relay, fuse links and a ammeter shunt to the starter before making it to the battery. To many chances for high impedance connections for my money. If you don't want the ammeter then I would re-wire the alt. wire with a #8 or #6 via a hefty fuse to the starter solenoid with the minimum interconnects. This would provide the cleanest low noise system possible.

Bullshark

P.S. Don't forget your ground ckt. It should be a good solid distributed ground plane thru out the system. Any impedance on that side of the circuit can be just as distructive.

 

This is just FYI and thought i might get you to think of a couple of other things that all this is going to effect.
What BullShark stated about having a clean system also reminds me of something else -When running control modules and distributors such as a HYfire 6 and a Unilite distrb- if the filterpower filter is not installed to get theses voltage spikes out of the system it will ruin the components.


Steve
I'm in the process of mounting my box. so if you want drop a line if there's anything I can help with.

 

with Gene

This is the best way. The alternator generates the power and it is the closest place to wire the fans into the system. No draw on the system. Tap into the wire between the alt and horn relay.

 

Jack, Actually the battery is the true source of power to the system. Think of it as a giant capacitor capable of suppling instantaneous current to meet transient demands of the system. True, the alternator supplies main power to the system when running but relies on the battery to keep control of the transient current demands and maintain a solid voltage with low noise. The alternator via its regulator acts to supply the raw regulated power to the system by turning the current on and off very rapidly to provide a raw 14v but is not efficient with large, high speed transient loads (like fan motors). It too can be a source of noisy power depending on system filtering. If you are suppling power to elements of the system that don't generate noise or demand clean power (such as head lights) then connecting at the alternator is a great way to keep short wire lengths and minimize voltage drop. Having said all this, if you keep good low impedance wiring and solid filtering and grounds thruout the system, it probably doesn't matter. But, these old cars didn't have the best electrical system in the first place and have a way of deteriorating (high resistance connections) over time. Providing a solid low impedance connection ( i.e. #8 or better wire with no resistive connections) from the alt to the battery/starter is the key


Bullshark

 

Bullshark, when you say "re-wire the alt. wire with a #8 or #6 via a hefty fuse to the starter solenoid with the minimum interconnects."

What is a hefty fuse? 30 amp? 60 amp? And should the fuse be on the alternator end or the starter end? Please excuse my ignorance, I'm by no means an electrical guy.

 

Good question...... I am essentially suggesting that you update the fusable links that are already present with something new and refreshed. They have a way of deteriorating. I can't remember what its rating is. I will check and get back to you (maybe one of the other guys remember?). The new cars use big slow blow fuses but a fusable link is probably just as good if done right. After that a wire bypassing the other crap is all that is needed. ( But, Only if you don't use the ammeter because this will cause an error in the reading) Both Spal fans together only draw ~25 amps peak at start-up while running at ~11a steady state. if my memory serves. So the present fusable link probably has enough margin to handle that.

 

http://www.madelectrical.com/electri...evymain2.shtml. Go to this site, using this schematic I wired my 135 amp alternator in this weekend, I also have the spal fans. I used the part 3 schematic, my lights are brighter and do not flicker at idle when the fans come on, the guage hardly moves when the fans come on. MAD electrical is a pretty knowledgeable company.

 

Tankers, did you leave the starter solenoid at the starter or move it back to the rear as the MAD system recomended? I do like their recommendations if re-wiring the engine compartment is in your plans. The idea of a firewall mounted terminal strip (buss bar) regulated to the 14.2 volts acting as a central distribution point is very appealing. Notice the large #8 gauge wires from the "regulated" terminal strip to the alt as well as to the high current loads (fans and lights).......and a relatively short #10 gauge wire with the 14 gauge fusable link connecting to the battery via the starter solenoid. With this system you could wire the fans to the terminal strip or the horn relay which ever is more convenient. Thier schmatic doesn't show it but we would have to route the voltage sense wire from the alt down to the terminal strip rather than the horn relay where it is presently located. I think I would use the existing solenoid as is and buy a cheap terminal strip and wire up per the schematic. Probably saves some money.

Bullshark

 

I left the starter solnoid on the starter and ran a 6 gage wire from the alternator to the distribution point, then another 6 gage from the distribution point to the battery. Ran it through the firewall, under the carpet, up the side trim and out through the carpet into the battery compt. Can't see it. Then I ran a 8 gage wire from the distribution point to the fan wires which I have located by the horn relay. I could have ran the wire to the horn relay then hooked the fans to the relay, I chose to go straight to the fans. I then took the A/C relay wire and the dash power wires off the horn relay and ran them from the distribution point. I left the 12V wire running from the starter to the horn relay hooked up to the horn relay. The powermaster site has a chart for the size wire to run from the alternator by how much amp the alternator can put out and how far you will run the wire.

 

Thank you gentlemen. I think I'm getting to understand it now.

 

Just a couple of more questions please.
The Voltage Sense wire is one of the wires off the 2 prong connector on the alternator I take it?
Also I take it this wire gets wired to the new distribution point in the schematic so it can sense the voltage at that location?

 

Q1) Yes, it would be the wire that goes to the horn relay off of pin 2 of the alt connector. (black/white on mine) The other wire (pin 1) goes to the ignition switch (brown on mine).

Q2) Yes

Bullshark

 

I talked to the main guy at this company, and they are super great
when I changed over to the serpintine setup with the 100 amp alt,
I keeped having problems. After 30 minutes on the phone, this guy
explaine in detail how everything works, and the do's and donts.
After seeing how willing they are to help I bought a simple 28.00
kit to keep my 2 wire alt, instead of going to a one wire.

thanks for posting his site TANKER, I knew it could be done, I just
diden't know where to turn, because I did not want a one wire setup.