Here is the stampings:


My radiator has sprung a leak and I'm going to replace it soon and am thinking of going electric fans. Just gathering info so I'll be ready for electric fans mod if I decided to go that route. Also what is the typical current draw for electric fans (I know some will draw more than other just a ballpark figure) and will my current alternator have enough to work. I'll upgrade my wiring as necessary for the fans and install relays etc.

 

1105606 comes up as a 94A alternator but assuming you have a 71 that is not the original alternator
https://www.rareelectrical.com/i-269...6-1105425.html

 

Yes, '71, not original.

 

My dual Spal setup draws just shy of 30 Amps when both fans are running at full blast. Which is only when I'm stopped at a light. They have a single temp switch controlling both (separate relays), but you could stage your system and perhaps never see the second fan come on.

 

Who knows what's inside it? Just sayin- I see a lot of L88 hoods!!!

I'm fortunate - have an old school alternator guy near my mother in laws. Actually rebuilds them - tests them and made sure there was no vibration at speed.

Seen too much junk out there. I also had him get the smallest pulley so I'd get more juice at idle.

It's well worth the money to get a PWM controller for your electric fans. Keeps the initial start up current in check- and varies the speed as needed- just stick the sensor on the radiator.

https://www.summitracing.com/parts/der-16796

 

Ya, I 'm going with a PWM.

 

But do you really think someone would open the alternator and say yeah I want to make that 94 amp alternator a 40 amp alternator and im going to replace the 94amp stator even though they virtually never fail?

OP Im running the dual 11" becool/ spal units with a 105amp alternator and I have the derale controller and agree they are worth it for drawing less unnecessary current. (I dont have the pwm one) Mine only turns one fan on at a time with the second one 15 degrees higher that the first so it rarely runs. But as a test I disabled the first fan and let the temp climb to like 185 and then enabled both fans to come on, while running my headlights and wipers, heat and stereo and my alternator still put out 13.9V -14v at idle with all that running meaning it still was charging the battery and not even using it as intended. I have a powered stereo amp as well. I did this because I was incorrectly told that the high output 12SI would not put out enough amps at idle and I really needed to go to a cs130 amp from the stock 40amp alternator because the of the additional 30a draw.. I suggest you not over think it and install the fans (correctly) and see how the alternator does. I think you will find you have no reason to upgrade it. Some people do ... My 105 a chrome alternator just happen to be the cheapest sub $70 alternator available on ebay at the time a few years back..

All this is of course a moot point anyway unless the car spends very long periods of time idling in traffic anyway as with normal driving the battery will act as a reserve for these situations.
I have these fans which a number of people run here without issues. https://www.ebay.com/itm/27187068412...8AAMXQ~6VQ7kxV

 

Try it. Worse comes to worse go get a 140-amp CS144.

I had a 94 amp 12SI and it did ok until I ended up with a Mark VIII fan, EFI & associated electric fuel pump, and Air Conditioning. Then it just could not maintain Battery Terminal voltage at idle.

No other way to spin that - it's a FACT.

I swapped in a 140 amp CS144 and it maintains >13.6 VDC at idle at all times. I had a problem with my CS144 (bad connection) so I swapped the old 94 amp 12si back in just to ensure the system was working ok .... and sure enough, it does fine at speed but just CANNOT maintain battery voltage at idle. Just the way it is. As long as you don't have too many loads to run at idle (just the electric fan for example) the you should be fine.

 

These pieces are 40-50 years old- no telling what could be in them- just because the case says 94A.

 

That all im saying... try it you dont know what your combo needs unless you try it or know the exact specs and current needs of your accessories.

Good point if someone has AC as well as other aftermarket changes already like EFI and the electric fuel pump.
GM boosted the stock alternators 20amps from 40 to 62a just for the AC.. so you have the electric fan, fuel pump and efi all competing for that extra 32 amps the 94 amp gives over the 62amp stock model and the fan alone probably draws close to that plus they are not rate for amp output at idle. I dont think there are a whole lot of aftermarket EFI C3s out there though let alone EFI converted c3s that arent already upgraded to an electric fan (I could be wrong).. It also should be said that many aftermarket/rebuilt high output alternators advertise higher output at idle than stock setups (mine puts out 14.5-14.6v which is on the higher side voltage wise) so that may also explain why some work fine and others need such large oem style alternators.

My output at idle drops from 14.5v to 14v with everything I could think of running at idle.checked with 3 different meters including my gauge and multimeter and a phone charger I have with a voltmeter built in. I do have LED lighting which draws less current than stock, my stereo amp is a measely 250w and my AC doesnt work... To be fair if I had AC and had a scenerio where everything was on in the rain at night for long enough periods of time without moving... my battery might get run down. YMMV

 

Just try it. Worse comes to worse you go buy a 140 amp CS-144, an adapter to your 12si connector (assuming you don't want to fabricated something), and maybe a new belt.
I got the best looking 140 amp CS144 at the boneyard for 22 bucks years ago and they're more common now.

 

Thanks for all the good info.
I've never tried it but I have a current clamp for my multi-meter. I wonder if it will show current draw out of the alternator. I don't think it will since the voltage is DC at the point of coming out of the regulator and I think my meter/clamp can only do AC. I will try it and see what happens.

 

What Fluke do you have? It should say if it will read current at 0 Hz. The really expensive ones do.

Another option is to use a current shunt of the appropriate size (cheap at Amazon), then you measure the voltage drop and do some math. The alternator will only put out whatever current is being drawn, so if your battery is fully charged, you won't see it put out full current.

I don't know if the alternator testing at Advance or Autozone or wherever tells you an actual number, but that might be the easiest way. I assume they have some kind of adjustable resistive load, but perhaps I assume too much.

 

It's a Fluke 87 series III. It will do DC but I don't have the right clamp. I found the manual but it's an inch thick. LoL

 

Unless you are really determined to find out what amps are being drawn, you can otherwise just take terminal voltage readings at the battery to ascertain alternator performance as follows:
1. Battery voltage before starting the car.
2. Battery voltage at idle with the electric fan NOT running.
3. Battery voltage at idle with the electric fan running at full speed.

Rough Expectations for above readings:
1. This battery voltage should be somewhere about 12+ vdc.
2. This battery voltage should be somewhere between 13.5 to 14 vdc
3. This battery voltage should be somewhere between 13.25 and 14 vdc (and probably more like 13.5 vdc to 14 vdc if the voltage regulator is reacting properly).

Those are rough values for expectations but you get the idea.

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My main concern is the original charging wires being too small for the increased current draw. I'm just going to replace those wires with a larger gauge. Once I do that I'll fab a terminal block and relay to power up the PWM and fan circuit.

 

Yes, you will want to add a second 6awg wire going from the alternator stud to the stud on the starter Most directions for the alternator wiring kits will also tell you to leave the original wiring in place when adding the second larger wire. This is what I did as the directions from the "tuff stuff" alternator wiring kit advised me to.. The wire from the starter to the battery is already sufficient enough and since your goal is to have enough power to always power the fan from the alternator anyways there shouldnt be any additional draw through the wire between the battery and starter regardless. The best place to power the fan relays from would be the starter connection. I also added a battery gauge since the wiring changes will render your ammeter useless. The gauge will tell you if your alternator is keeping up since if its not you will see your battery voltage dip down to 12.6 or so.

 

I have a 1968 C3 and recently put a 120 amp alternator after having issues with a smaller alternator in it. (As per the manufacturer) I installed a new heavy #4 Flexible Welding wire and ran it straight to the battery post on my Starter Motor. This works great for charging but what about the power to the rest of the Corvette?

(By the way we are dealing with an early October 1967 dated 1968 (Built at a foundry in Tonawanda, N.Y.) 427 Corvette Convertible, with Four speed and Power Steering and Power Brakes and the AM-FM Radio. It is a Basic Non-Air Conditioned Corvette so it came with a tiny alternator by today's standards.)

On my C3 there is a wire that attaches to the Horn Relay that supplies 12 volts when running. ( Please tell me if you know different.) When I put 12 volts to the relay, the Fuse Panel gets it Power and comes back on. I have not measured the current but want to. Is this the original route of the Battery (Positive) Charging System?

What is the best way to make this old Corvette and it's Owner Finally get this charging system working the best I can? I like a reliable Charging system and I just need to see that the fuse panel gets it's power AND charge the battery through the Starter Solenoid.

Any advice would be helpful. This Car and I have been together now for over 30 Years and has been a lot of fun for my family. I am just making some upgrades and want to keep all the systems "happy" so the parts last a while.

 

all you need is to beef up the wiring from the larger alternator to the starter as you said. any additional power wires should be run from the starter. Unless your trying to tax the other wiring such as the horn relay power terminal by trying to run more accessories off of it, Theres no need to beef up that wiring. and the wire from the starter to the battery is already oversized from what it needs to be to supply power to the accessories because it has to be to power the starter momentarily while starting the engine. After that, the large 4awg or 2awg? wire does not have much load on it at all if any other than whats going to the battery to charge it since everything else is being powered mainly from the alternator.

Others can explain why better than me but you do not want to power things such as the fans directly from the alternator. This is due to both the crude modified ac waveform the alternator puts out which the battery normally acts as a smoothing capacitor to buffer out more or less and the strain that would be put on the alternators diodes if you did. powering these things from the starter with the short heavy wire to the battery allows the battery to perform this function better than it would if you tried to power it from a separate terminal port directly off the alt stud. Hopefully this makes sense.

 

On my 1968 C3 it has a wire that goes from the alternator or someplace where there there is 12 volts and that has to feed the Horn Relay.

If I don't run a wire to supply power to the Horn Relay (while running) then my Dashboard items and Fuse Block don't get any power. Is this normal for a early C3?

I have studied the schematic for hours trying to makes heads or tails out of the charging path. When I supply power to the Horn relay then my fuse block is powered.

Does the output of the alternator go through the ammeter in the dash?

I do not run any accessories from the alternator output, everything is powered by the battery. Thanks for your thoughts!