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Upgraded alternator and wiring to accommodate upgraded fans, voltage drops to 12.5v at idle when fans kick on

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Hey guys! Got some electrical questions for y'all. Pretty much lowdown of the electrical setup. I have electric fans, water pump, fuel pump and vacuum pump (to help booster due to low engine vacuum). I had a Summit 100amp alternator on it, but with this supercharged big block when it would get warm here in Florida it would get up in temp. So my plan was to upgrade to these Spal fans off Summit. Due to the upgraded amp draw from the fans, they recommended a 40amp fuse and relay per fan. I also have a aluminum shroud for the 14" fans that cover the whole radiator, which is a 28" 4-core Champion radiator. The v-belt is only spinning the alternator.

I have my battery located in the "back" (smugglers box of my El Camino), with 2 gauge wiring from the alternator to battery. I bought a Tuff Stuff 140 amp alternator and am currently using the 1 wire setup to use my 2 gauge wires. I made a panel for the under side of my dash to move my relay fuses and distribution closer to the front and clean up my wiring, so basically the 2 gauge power wire from the alternator goes through a 100amp midi fuse, to a distribution block and the rest of the 2 gauge wiring goes to the battery. at the distribution block I have 3 10 gauge wires going to a separate small fuse block to power my lower amp fuel, water and vacuum pump. For the upgraded fans, I have an 8 gauge wire going to a 2 fuse box, that splits to 10 gauge wires going to the fan relays in the engine bay, and to be on the safe side we'll say its a stretch of 10' of wire (I have everything tucked). What concerns me too is the fan wiring that comes with the fans doesnt even look like 10 gauge, looks like 12. Wouldnt that cause a choke running that many amps across that long of a stretch from the fuse to the relay to the connector then drop from a 10 gauge to a 12?

So I talked to Spal about the fans and what their amp output was, and I was told at 13v each fan would require 19-21.5 Amps, which seems low for what the upgraded fuse and relay requirements they have are.

So anyways heres my issues. When I was burping my cooling system in park, when the fans kicked on they moved a **** ton of air, and actually dropped my temp down from 180 to 165/170° which surprised me as ive never had that happen before, before with my old setup it would get to 180° and stay there (granted if its not too hot outside). Later on went out to pick up pizza about 2 or 3 miles away, car drove great, but pulling in the lot at like 1000rpm slight gas, alternator v-belt started squealing (slightly embarrassing, but cant really hear over the exhaust lol) and when I stopped, I noticed my volts were at 12.5v. I assumed the v-belt needed to be tighter and was low voltage due to it slipping. Picked up the pizza and drove home with no other issues, when I'm cruising im at 13.8-14v on my volt meter. At home I tightened the belt and was going to drive it to work tomorrow.

Drove it to work about 15 miles away with no problems, stayed at like 175° but again at idle after a little while I noticed my volts dropped again to 12.5v. Lunch time drove down to get more pizza about a mile with no problems. Driving home was about 88°F outside, nice day, and I knew at this point that my voltage was fine til my fans kicked on. So at the eternal light I was at, I watched my temp get to 180° and sure enough when I assumed my fans would kick on my volts dropped to 12.5v, and would fluctuate from that to like 13v, then kinda settle mid to high 12v. I put the car in neutral, about 900-950rpm and my voltage jumped back to about 13.8-14v. After a while of mostly stop as traffic lights here suck and my car at 12.5v at idle in drive, my temp started climbing to 190° which i figured wouldn't happen cuz it was a nice day outside, but I assume its cuz my fans arent pulling their max amount if my alternator isnt putting out at idle what I'd like it to.

I get home, and put it in park and let it idle the temp dropped from 190° to 180°, which leads me to believe the fans help cool the car fine, its just they need to be at 13.8v to be doing it. I had my partner help me while I tested voltage on the alternator pos to alternator case in park and drive. Park was 13.8v, drive was 12.6v. I tested pos and neg. terminals on the battery and same readings. Did a voltage drop test from the pos. alternator to pos. battery, was 0.1v, same for alternator case to neg. battery terminal. I was mid process of doing voltage drop from alternator to fans but I was so physically and mentally exhausted from how much I've been working at work and side jobs lately I had to go lay down and take a nap. So now I figured i'd post this and get your opinions and thoughts and what to test/look for. My other alternator never went this low, then again I didnt have fans as strong as these before. I need to get an amp clamp too to get a good idea of how much some of this stuff is pulling/moving.

Heres some pics of my gauges from the drive, first pic is in drive, second pic is neutral with slightly higher rpms and higher volts. (volt gauge is the top gauge on the 4 gauge piece)




Thanks for your help!
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Sounds like it isn't being spun fast enough maybe??

I tried to look up amp output @ rated rpm to see what the output curve looked like, but Tuff Stuff doesn't provide that info lke some others do.

Nobody's alternators make the full output at idle, most need a certain amount of shaft RPM to put out full amperage. Note you've got pulley ratio's in play, when a company gives rated rpm for an alt, it is alternator shaft rpm, not engine rpm.

I think you've pretty much figured this out by showing that just a few hundred engine rpm increase between idle in gear and idle in park more or less fixes the problem.....sounds like you need a smaller driven pulley(alternator) or larger drive pulley(crankshaft)
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ericnova72 said:
Sounds like it isn't being spun fast enough maybe??

I tried to look up amp output @ rated rpm to see what the output curve looked like, but Tuff Stuff doesn't provide that info lke some others do.

Nobody's alternators make the full output at idle, most need a certain amount of shaft RPM to put out full amperage. Note you've got pulley ratio's in play, when a company gives rated rpm for an alt, it is alternator shaft rpm, not engine rpm.

I think you've pretty much figured this out by showing that just a few hundred engine rpm increase between idle in gear and idle in park more or less fixes the problem.....sounds like you need a smaller driven pulley(alternator) or larger drive pulley(crankshaft)
Click to expand...
I agree, they did give a little bit of info for Alternator max rpms, they say no more than 18000, and a formula for figuring that out (crank pulley diameter ÷ Alternator pulley diameter = ratio, then times by max engine rpm in my case I'm limiting to 6k, so I'll probably look into what the current alternator pulley size is. I have a Good Vibrations crank pulley that's 6.25" in diameter, I'll update tomorrow
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joe_padavano
stanley9875 said:
...and am currently using the 1 wire setup...
Click to expand...
One of the fundamental purposes of the factory three wire setup is to run the SENSE wire all the way to the junction block to allow the voltage regulator to control voltage at the load, not at the alternator. GM engineers weren't as stupid as some people think...
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In my case , the power feed to the fan is wired directly to the alternator , about 12" of # 10 wire to the relay , then relay to fan , when the fan kicks in , there's no noticeable change shown on the voltmeter that's connected to the distribution panel under the dash.
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joe_padavano said:
One of the fundamental purposes of the factory three wire setup is to run the SENSE wire all the way to the junction block to allow the voltage regulator to control voltage at the load, not at the alternator. GM engineers weren't as stupid as some people think...
Click to expand...
And I've heard that about the 1 wire setups, and how a 3 wire is more effective than a 1. Ive also been reading this MAD electrical article about the benefits of 3 wire to 1 wire, but I'd just like some advice on how to wire it since I havent wired one up from scratch and want to understand better how it works.

My Summit and Tuff Stuff say there 1 and 3 wire compatible, just remove the plug where the 1 and 2 terminal are and hook up the connector. Well when I wired my car with the Painless wiring I didnt wire those, nor do I have an "idiot" light on my gauges... nor do I really think I need one.

According to this diagram I found, the #2 (or pin listed as 1 on the alternator) is the "idiot light" wire that I dont need to wire, correct? And the #3 (or listed as 2 on the alternator) is the sense wire that youre saying I should wire to that distribution block I have inside the car correct? And that'll help apply proper amps and voltage even when at idle?



Here are the instructions for my current Tuff alternator. Again, since I dont need an idiot light, all I should need to be able to do is run the 2 terminal to my distribution block, which will then help the alternator put more out when my fans kick on at idle correct?


Thanks for your help
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3repete
I didn't read everything as I understand it should be. Is your main positive wire going to the starter, then the alternator? It shouldn't matter but that's conventional.
From there you can branch it off to the loads.
I hesitate to say this because you sound like someone who does not need to be told, but be sure the battery is strong, of appropriate rating and fully charged. And that all wiring is fresh, with clean contacts and good grounds. No green corrosion inside the jackets.
And I agree with increasing the drive ratio on your alternator. You have lots of electrics on there taking up amps.
I looked up your load, at 22 amps 10 gauge will only drop .25 volts in 12 feet, so it isn't drop.
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3repete said:
I didn't read everything as I understand it should be. Is your main positive wire going to the starter, then the alternator? It shouldn't matter but that's conventional.
From there you can branch it off to the loads.
I hesitate to say this because you sound like someone who does not need to be told, but be sure the battery is strong, of appropriate rating and fully charged. And that all wiring is fresh, with clean contacts and good grounds. No green corrosion inside the jackets.
And I agree with increasing the drive ratio on your alternator. You have lots of electrics on there taking up amps.
I looked up your load, at 22 amps 10 gauge will only drop .25 volts in 12 feet, so it isn't drop.
Click to expand...
Thank you for the reply. And if theres one thing I've learned being a mechanic, is to cover all the basis, no matter how small/silly it may be.

Anyways back to the alternator concern, yes battery is a good Optima red top that I put on the trickle charger when I know it'll sit for a few days.

All my grounds are 2 gauge, from battery negative to frame (thats sanded down to bare metal at the contact point), frame to engine block, and frame to body. Overkill? Maybe but its clean and eliminates any issues with lack of ground. I also checked voltage drops for the ground to battery negative which were all 0.2v or less.

This is also an update post as I was out messing with it today after work. I have a Painless kit in the car, and found the alternator exciter wire I had tucked in my loom. Added that to a connector pin 1, and pin 2 ran to the distribution block and also tried a jumper to the pos. post on the alternator running back to the battery. Had the same issue, when in drive and 180F the fans kick on voltage drops to 12.5 (even a little less) unless I get the rpms back up a bit by giving it throttle or putting it in neutral/park. You can tell it affects the rest of my components including the electric water pump cuz my temp went up to 190 until I put it back in park and the voltage went back up to 13.8(ish) and the car cooled back down.

Also referring back to the wiring, no in short I have the battery in the back with a Ford solenoid, so starter is only getting voltage when key is cranking. That's why I made a separate distribution/relay panel inside under the dash to have my relay fuses and power closer to where they're going to (mostly the fans as they need a lot of amps).

So I guess tomorrow I was going to try and throw my other Summit 100amp alternator back on with that belt and see what happens. But at this point im leaning towards messing with the pulley ratio to get it to keep up speed at idle rpm, and I dont run this engine past 6k anyways.
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ProStreetRob
Some good reading here and as you will see the problem your experiencing is common with a 1 wire set up.
I just rewired my entire Chevelles Charging system using this simple wiring diagram and it works like a charm

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3repete
ProStreetRob, Was your charge system behaving anything like OPs?
Nice link BTW. Rabbit hole reading for me!
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ProStreetRob
3repete said:
ProStreetRob, Was your charge system behaving anything like OPs?
Nice link BTW. Rabbit hole reading for me!
Click to expand...
I just bought this Chevelle a month or so ago and when it showed up on the Carrier it needed a jump and immediately I could see there were melted and fused wires so it wouldnt even start on its own and everything was a messed up. So i ripped it ALL out and started over. I rewired from the Volt Reg & Horn Relay main Power Supply to Alt, Starter, Battery, MSD, new Headlight Harness, the whole nine... Now it's fine but I have a slight draw on the Batt I still have to find, but when running it charges like a Mo Fo... PS (i'm still in a battle with the seller and have gotten substantial money back)

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ProStreetRob said:
Some good reading here and as you will see the problem your experiencing is common with a 1 wire set up.
I just rewired my entire Chevelles Charging system using this simple wiring diagram and it works like a charm
Click to expand...
Good link Rob
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ProStreetRob said:
I just bought this Chevelle a month or so ago and when it showed up on the Carrier it needed a jump and immediately I could see there were melted and fused wires so it wouldnt even start on its own and everything was a messed up. So i ripped it ALL out and started over. I rewired from the Volt Reg & Horn Relay main Power Supply to Alt, Starter, Battery, MSD, new Headlight Harness, the whole nine... Now it's fine but I have a slight draw on the Batt I still have to find, but when running it charges like a Mo Fo... PS (i'm still in a battle with the seller and have gotten substantial money back)
Click to expand...
I have a whole Painless kit, part # 20102. This Painless kit actually supersedes my part #. But I have everything wired up to that kit, besides things like my fuel, vacuum and water pump and both my fans, which are controlled by separate relays. Youre wiring is still a possibility, but I'll still try swapping my alternator and playing with pulley ratios first as those are quicker things to mess with. I'll look at my wiring chart from painless and how I have other things wired up and see what i'll need to do if I'm going to try that diagram
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ProStreetRob
Ya I would try a different Alternator first and those Painless Harnesses are great so Im sure you have no issues there. You can also use a 3 wire Alt and just jump the #2 terminal back to the Battery or the main Alt Power, and not use the idiot light terminal at all, (Terminal #1 in the pic I'll attach). On a different note... You know its funny, and I dont know if it makes a difference but.... one of the things i realized in the Original Chevy Diagram is when you start at the Volt Reg with the two large red wires the factory has spliced together in what seems like a bad splice, LOL... The Diagram wants you to come out of that with two wires and have one going directly straight to the Alternator, then the other to the battery but through a fusible link first. THEY DIDNY HAVE MINE WIRED LIKE THAT. They had both to the Battery and then a separate wire to the Alt. Since they both come from a two into one splice I dont see the difference but I did mine that way and my Alt is charging like a mother now so that may make a difference if yours isnt like that ??? THIS IS NOT MY PIC, JUST AN EXAMPLE OF HOW TO HOOK A 3 WIRE UP WITH 1 POWER WIRE AND 1 JUMPER

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Hey guys I'm back with an update.

So basically I started off swapping the Tuff Stuff alternator out for the other Summit 100amp alternator I had on before with the other belt. Got that all sorted (just trying the 1 wire), got the car up to temp and put it in drive, as soon as the fans kicked on, dropped to 12-12.5. No luck there. I thought let me try hooking up the ground straight to the alternator case again to be sure. No progress. I tried the 3 wire setup again, hooked up the exciter wire to terminal 1 (I verified with my power probe its ground until I turn the key on then its 12v), and tried running the terminal 2 jumper to the alternator + where the cable going to the battery was, and even extended it (ghetto lol) all the way back to the battery with no change.

So at this point I'm just going to write off I need to spin that alternator faster at idle. I was looking at the instructions for the Tuff Stuff alternator, I think I mentioned this before and they said their alternator is not to exceed 18000rpm. My crank pulley I bought from Good Vibes Racing is 6.25". So 6.25" / 2.33" (the outside diameter I got off their pulley) is rounded up 2.7. Multiply that by my max RPMs which is 6k in my case, equals 16200rpm. So I still have room to play with, and I'm going to see if I can find a smaller pulley to hopefully spin my alternator faster at idle, since it seems to be a tiny amount of RPMs to get it to charge.

Ghetto test rig pic for your entertainment

And yes Pro Street Rob the Painless kit has been great 👌
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After reading your dilemma, I question the gauge of the wiring used - look at the chart I've attached , if you are running your Battery Cables in the bed you may have too small of gauge - remember, the chart says to include both positive and negative cables-total length of both.
Also, where (and how many) grounds do you have? Have you calculated your TOTAL system Amperage requirements (and added 20%)? If not, please do -I am running a 240 Amp Mechman Alternator (with a total Amp load of 170 Amps), and my Battery is approximately the same distance away as yours, however I am running 1/0 AWG tinned 4000 strand Cable, both on the positive and negative Cables (grounded to the Alternator, the Frame and the Block, then, head-to-head and then the Frame) and have had 0 problems-you can't have too many grounds.
My other question would idle Amps- many small Alternators (especially the cs130) are notorious for low idle Amps, and if you are driving this stoplight to stoplight (mostly under 3000 rpm) you still might not have enough Alternator-there should have been a testing tag on the Alternator showing your idle Amps, or maybe it's on the Tuff Stuff website (I know both my Mechman and the Powermaster (I've been where you are) before it had them-

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ProStreetRob


You my friend have a Work of Art Engine Compartment, Very Impressive, (3) Thumbs Up
Hope you get it figured out, hopefully spinning it faster will do the trick
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35WINDOW said:
After reading your dilemma, I question the gauge of the wiring used - look at the chart I've attached , if you are running your Battery Cables in the bed you may have too small of gauge - remember, the chart says to include both positive and negative cables-total length of both.
Also, where (and how many) grounds do you have? Have you calculated your TOTAL system Amperage requirements (and added 20%)? If not, please do -I am running a 240 Amp Mechman Alternator (with a total Amp load of 170 Amps), and my Battery is approximately the same distance away as yours, however I am running 1/0 AWG tinned 4000 strand Cable, both on the positive and negative Cables (grounded to the Alternator, the Frame and the Block, then, head-to-head and then the Frame) and have had 0 problems-you can't have too many grounds.
My other question would idle Amps- many small Alternators (especially the cs130) are notorious for low idle Amps, and if you are driving this stoplight to stoplight (mostly under 3000 rpm) you still might not have enough Alternator-there should have been a testing tag on the Alternator showing your idle Amps, or maybe it's on the Tuff Stuff website (I know both my Mechman and the Powermaster (I've been where you are) before it had them-
Click to expand...
Thanks for the tips. Yes battery cables are up to par. I have 2 gauge running roughly 13' from the battery to alternator. And while its 140amp alternator I'm not running more than 100amp more than likely. At most (overestimating) I have about 90amps with these new fans including the fans, water, fuel, vacuum pump, fuse box for lights, gauges, ignition box... no radio or A/C. I just figured 140 amp wont stress that other alternator out as much by being close to max output all the time. Plus when I got the Painless MIDI fuse to fuse the alternator I got the 100amp one and it hasnt blown yet 🤣 Basically right on the other side of the firewall is the relay panel I made where it has the distribution block that feeds power to my pumps and fans using the relays.

And I found out early in the build about grounds when I thought a 2 gauge ground from the battery to the frame would be enough for the whole car and my starter clicked first time trying to start the engine in the car. Added another ground from the frame to the block and it fired right up. So now I have a big ground cable from battery to frame, frame to block, and frame to body.

I saw the Powermaster brand has an amp testing tag on theirs, but my Tuff Stuff one didnt.

ProStreetRob said:
You my friend have a Work of Art Engine Compartment, Very Impressive, (3) Thumbs Up
Hope you get it figured out, hopefully spinning it faster will do the trick
Click to expand...
And thank you! You can see why running wiring like that to test was driving me crazy. Lot of work to get the wiring tucked and loomed!

So basically I'm going to have to spin the alternator faster. Unfortunately searching today has proven tough to try and find a smaller alternator V-pulley smaller than 2.25", and a larger crank v-pulley that'll fit my supercharger spacers. What I'll try to do is swap out the current Tuff alternator for a Tuff alternator with a serpentine pulley on it, and get a larger serpentine pulley that'll fit my supercharger spacers from BDS and try again
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You say your voltage drops to 12-12.5 , is that a problem ? How long do you normally let it idle for an extended period ? Is the battery going dead ? Does the voltage come back up as soon as you accelerate ? I don't see a " problem " .. If the fans won't cool the car at 12.5v ,it sounds like can cooling problem ,not an alternator problem ...:unsure:
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Stanley, your alternator is only a one wire job (but the vehicle 3 wires can be connected to it) it will NEVER be a real 3 wire alternator unless you pull it's internal voltage regulator apart n replace it with the 3 wire non-self excited type. Do as I am doin..............buy a 95 amp 3 wire alternator for a 85 Camaro n wire it to a main power junction box on the firewall (see Madelectrical article) n you'll have higher volts but make sure it's an AC Delco type 12 n not an aftermarket copy . I gettin mine shipped to the UK from DB electrical
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