from another thread over THERE, hear me out please...

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Quote:
Originally Posted by RunningMan373
I differ from DB on this, I think you should run your power wire, (I would recommend 8 gauge, but 10 will suffice), direct from the alternator, because it will be the alt that will be supplying the current when the engine is running with the fan cooling it, so it will feed the current directly into the fan.


If the fan is pulling current directly from the alternator then the alt will never see the battery's actual charge, and the internal voltage regulator will not be able to properly keep the car's electrical system at a specific voltage. By wiring the fan to the battery, or even the starter lug from the battery cable, the alternator will sense actual system voltage and keep things regulated properly.



OK, I agree with running man, and my DVM tells me I am correct....now with typical fuse link factory wiring.....is DB brain baskin correct or am I for agreeing with Running Man above.....I have not posted about this topic on that thread or any other recently as I don't want to get involved in another hornets nest.....

so is there any variation of these sharks that allows the battery cable on the starter direct to the high current DRAIN is in fact better??? or any other car wiring practice for that matter???

so what is the final disposition of this case, guys....I have was left in the dark the last go round some year+ time ago....

I still think I"m right, but if some engineer can tell me I"m rong and prove a good arguement, I"m all ears....

:tomato::cussing:

As I recall, the alt output was fine for relay control, and the battery was necessary on Baskins PWM controller for spike suppresion.

Gene,

did you ever put an oscilloscope on the alt and battery and compare signals?

a meter won't cut it.

turtlevette said:

Gene,

did you ever put an oscilloscope on the alt and battery and compare signals?

a meter won't cut it.

Click to expand...

ON the alt stud only....500mv of ripple with some drain, with a/c on and all fans running full force 700 me ripple....woopie doo....

never did measure the battery though...as the fans don't connect threre...pia to change that around....

fail to see why a lousey 1/2 volt of ripple on a 13.6 volt line would upset some controller....still think any heavy load like that would leave a voltage drop across the fuse link or any wiring which the battery gets less than a full 14.7 volts for charge and proportionally less overall...and the alt dunno anything is rong....

NOW, if the alt typical red wire to clockwise #2 wire looking from backside was connected to the starter bat wire instead of the harness directly....I can see it working good, IF the fuse link is fatter to carry all currents adequately...

:crylol:

Ok, I will give this a try. :suicide:



The above schematic is close to what we have in our C3's, except, the sense (#2) wire is connected to the horn relay bus bar. That bus bar is our regulation point that the internal regulator controls to ~14.3volts (13.6v ??) The regulator does this by controlling the field current to drive the Batt output voltage to the level that is determined by the resistor divider R2 & R3 in the regulator circuit above. This is essentially a feedback loop in an amplifier circuit. As a rule you don't want to introduce noise/spikes in an amplifier feedback circuit or you run the risk of making the thing unstable. Obviously this depends on how large the spikes are and how fast the rise and fall time is. Connecting things like high inductance fans, capacitors etc. can introduce poles and zero's that affect stability. Larger gauge wires reduce this effect, but we are talking potentially very high frequency here and very narrow spikes can toast sensitive electronics like EFI computers, and Baskin PWM fan controllers. This is hard to quantify not knowing exact circuit values, but it is just safer not to hook anything directly to the alternator +Batt terminal in favor of the horn relay bus. However, a single wire alt. has the feedback loop closed internal to the alternator so, connecting to that terminal is safe.

Remember Gene, just measuring the continuous output noise (.5v) is not telling the total story. Unless you have a properly triggered storage scope you probably missed the big spikes that were there when the fans turn off and on. The battery has a very low source impedance and acts like a big capacitor keeping the 12v source very clean. I do not recommend connecting the fans to the starter because it pulls high current thru the ammeter and screws up the battery charging circuit. Best place to connect noisy stuff is the single point voltage source like shown in the MAD diagrams. (aka horn relay bus) I don't have a MAD schematic handy though. Does any of this make any sense???? :flash: Cardinal rule is connect sensitive electronics like ECU's directly to the battery.




Bullshark

Bob, who drew that second schematic you have there??? the ampmeter would be a traditional mv meter across a shunt, which is not the case for a factory wired shark.....

second, you post prompted me to go look up some things on my computer wiring.....I have the injector banks on steady feed from the horn relay/alt output, allways live, along with the main power for the fuel pump...a ~7 amp fuse feeds it all....the 5 volt reg needs a 12 volt feed which is also high side of the FP relay....that is switched by the ign, AND my anti theft device....

I have to get under bright lights and a magnifying glass to follow my old factory '87 vette diagrams for fan hookups, and I just spent 5 minits trying to read that blinding diagrams.....no go....hell, I can't even FIND the battery on there, just the ref to the batt cable with 3 heavy red wired going there....at the starter, I presume...

OH SHIT, off to the electrical diagnosis manual part 2......

there is the diagram I need.....showing 11 fusible links...and sure enough the fan has it's own fuse link off the battery directly....with another fuse link from the alt B+ output to the battery....which is where the regulator gets the ref from also, of course...

humm, been a long time since I sold my '87, so no lookey at the schematics...so in fact, my '72 has been slightly shortcutted in the wiring from the oem '72 wiring, to the later wiring...I have just two fuse links in the entire harness....plus of course fuses....and no other actual electronics but the engine computer at this time....:waxer::flash:

mrvette said:

Bob, who drew that second schematic you have there??? the ampmeter would be a traditional mv meter across a shunt, which is not the case for a factory wired shark.....

Click to expand...

Dunno....I found it somewhere on the Internet and thought it might be a good communication diagram. You are correct about the shunt amp meter. That is not shown in the simplified schematic.

there is the diagram I need.....showing 11 fusible links...and sure enough the fan has it's own fuse link off the battery directly....with another fuse link from the alt B+ output to the battery....which is where the regulator gets the ref from also, of course...

Click to expand...

I agree, nothing wrong with also running the fans directly off the batt. as your 87 diagram apparently shows and provide a separate regulated B+ terminal (similar to our horn relay bus) for regulated battery charge control. That would help keep the noise generated by the fans at a minimum. I just don't like to use the alt. battery charge wire to supply part of the fan current, which is what happens when the fans are connected to the starter in our old C3's.

Bullshark

Bullshark said:

mrvette said:

Bob, who drew that second schematic you have there??? the ampmeter would be a traditional mv meter across a shunt, which is not the case for a factory wired shark.....

Click to expand...

Dunno....I found it somewhere on the Internet and thought it might be a good communication diagram. You are correct about the shunt amp meter. That is not shown in the simplified schematic.

there is the diagram I need.....showing 11 fusible links...and sure enough the fan has it's own fuse link off the battery directly....with another fuse link from the alt B+ output to the battery....which is where the regulator gets the ref from also, of course...

Click to expand...

I agree, nothing wrong with also running the fans directly off the batt. as your 87 diagram apparently shows and provide a separate regulated B+ terminal (similar to our horn relay bus) for regulated battery charge control. That would help keep the noise generated by the fans at a minimum. I just don't like to use the alt. battery charge wire to supply part of the fan current, which is what happens when the fans are connected to the starter in our old C3's.

Bullshark

Click to expand...

Which was the basis of my arguement with Brain Baskin over 'there'....some time ago....

:drink::banghead:

mrvette said:

Which was the basis of my arguement with Brain Baskin over 'there'....some time ago....

:drink::banghead:

Click to expand...

Guess I got confused, For some reason I thought you were taking the position that connecting the fan load to the alt Batt+ terminal was best? As I remember he took the position that that was a no no. FWIW....That was about the only thing I agreed with the arrogant azz hat on.

Bullshark

Bullshark said:

mrvette said:

Which was the basis of my arguement with Brain Baskin over 'there'....some time ago....

:drink::banghead:

Click to expand...

Guess I got confused, For some reason I thought you were taking the position that connecting the fan load to the alt Batt+ terminal was best? As I remember he took the position that that was a no no. FWIW....That was about the only thing I agreed with the arrogant azz hat on.

Bullshark

Click to expand...

NOPE, other way around, IF the fans were allways on, say under a/c request...so the fans are a spinning, drawing current in an hour's driving stuck in traffic....so the car is cool, but the .bat is not seeing full charge currents...because of the voltage drop across fuse link or any wiring into the .bat circuit....the voltage sense is taken much closer to the .alt end of things.....

which is why I put really heavy current devices to the .alt directly, for the engine fans, they wired ~8 ga directly....Dual Spals and a on/off relay....
fused through a link...about 2" worth.... on these old sharks, the fuse link is about ~1ft long....I trust the fact that GM also put the high speed blower relay off the horn relay/dist term through a 30 amp fuse up top well away from the .bat.....

as noted above the '87 has the entire issue covered like a blanket as only the factory can....frankly no hotrodder is building a dozen fuse links in addtion to that fuse block/panel in the pass door jamb.....
I remember looking at that panel when buying the car ....lawng time ago..and immediately ordering the factory GM manuals I still have....

SOME things I can weed through pretty good....but....I 2 have limitations....

:ill::bomb::gurney::evil::banned: