Alternator Upgrade Due To Electric Fan

Today I drove maybe 10 miles in terrible traffic in my jeep to take my son to lacrosse practice. Everything went well except for the annoying traffic. Electric fan running the whole time, voltmeter is around 14 volts, maybe a bit less. On the way home in the dark with lights on and electric fan kicking on in much better traffic, at idle it runs a bit more than 12. Off idle i get more volts, but not a whole lot more until I take off driving. This either turns the fan via the airflow and decreases the draw, or the alternator needs more RPM speed to produce more current.

its a 61 amp externally regulated model. The belt is tight and the battery is ok. Not a great battery, but just ok.

I dont mind the external regulator. Can i just use it and install a higher current producing alternator? Do you guys have one that you use that remedies this issue?

What would you do?

 

I'd go with one of those single wire GM 10si or, is it a 12si. There was just a thread on here somewhere about it. Don't think it's a difficult installation. Cleans up the wiring a bit, and there are replacements on every parts shelf in the country.

 

Yeah, but I read they don't make juice at idle. Thats where I am at now. The electric fan draws enough current that i can tell it clicks on before I can hear it because the engine loses some rpm. Not a lot, but enough for me to notice.

 

Pulley size might be the answer. I will see if I have one. The Alternator is a 3 wire with external regulator form a 1965 buick skylark.

 

Just went through that very question today on a new drive kit I'm putting together.............Got myself schooled and aged today when the Alternator options were either 170 or 250 Amps.......I told the ole boy I remember when a 60 Amp alternator was an option?...........You can try spinning it faster with another pulley but those fans are very hungry for power at low RPMs

My new one ....106 at Idle / 150 at cruise / 168 top end

 

Seems that the eternally regulated delco/remy alternators had a top amperage rating of 61/63 amps. I only have trouble driving at night with this and do that seldomly. The remedy is to go to a 10 or 12 SI like Tarry posted above. The power masters are expensive, but good quality units.

here is a great article about the 10 and 12 si alternators Catalog

If I had a free Buick 350 crank pulley, I would do that. A rebuilt 94 amp 12 SI from a 1984 camaro with a 5.0 engine is the suggested list for the alternator. More Information for REMY 202661 it is 67 bucks with a 20 dollar core charge included not including shipping. I will have to rewire something to install it.

I am not sure this will automatically fix my amperage problem at night with the lights on and rad fan at 650~750 rpm idle speed. My present setup shows 12.5 volts on the voltmeter in that condition , but that might only be what the charge is in the battery. Eventually it will cook the battery and cause it to over heat and fail. Night driving is not something i do for long duration...

 

Go to junkyardgenius.com It will answere all your questions on alternator upgrades. Also includes wiring diagrams ect... Section on Delco Si series alt info and upgrades. Other great information on site! I would dump the externally regulated, although it is working correctly. But that has never stopped me from an upgrade. I usually try to do the opposite of what my wife thinks I should do. Hope this helps.

Cole

 

I am a big fan of 10si alternators. I am not a fan of 1 wire alternators because of mostly the cost and availability, on anything but what they were designed for, old tractors. I do keep one on the shelf for those that want the ease of just connecting 1 wire and forgetting it. The regular 10si is very very very easy to wire. About a 2 on a scale of 1 to 10 upgrades. A 10si gives you a charge light when hooked up and does not need a bunch of rpms to excite. The charge light can help you if you lose a fan belt and stop you before you overheat your motor. Every flaps on the planet most likely stocks several of them. I usually go with a 78 c10 for an application and they usually run between 30 and 35 dollars. Once wired they you can choose all kinds of amperage outputs to meet any specific draw if a 63 amp unit isn't enough. A normal 63 amp output will easily run almost any rig that has a good battery although. If you have a thumping stereo with multiple amps or spend a lot of time pulling cable and winching, you may want a higher output unit.
http://www.autozone.com/batteries-s...-5-7l-4bl-ohv/333906_2177_4676/?checkfit=true

 

The 10 Si tops out at 63 amps. Thats where I am now with my present rebuilt unit. I do not have a charge light, but a volt meter. Its an externally regulated model and its fine, except at night, at idle, with the electric fan pulling current. I actually am at a loss as to why it is running at like 12.5 volts at that scenario. Maybe my battery is taking a dump or the electric fan motor is not particularly efficient. Off idle or idling and non night driving it charges at 14 volts or so regardless of electric fan function.

 

Your gauge is indicating 12.5 volts with fan and lights on. It definitely will draw current and load down voltage. But it could possibly be due to where it is sampling voltage from. Think of it as a river with small streams branching off. The river might be flowing fine but you are using a lot of water, so the streams might suffer(high current draw). I would directly check the battery voltage with fan and lights on with a digital volt meter. Put it on the terminals of the battery. You should see 13.8-14.2 volts for normal charging of battery. It may not quite get there at idle, but close. If you figure your lights are pulling 30 amps and your fan is pulling 15-20 amps. So math for marines says 45-50 amps, give or take. But I assume your fan is temp controlled, so your about 30 amps at night on the go. And the rest of your draw is HEI and what ever else your running.

 

The charging voltage reads 13.75~14 volts DC at idle with the fan on or off. It only dips to 12.5 when at 650or so RPM idle with fan on and lights and brake lights on, then comes up to normal ,13.75VDC, above 1200rpm. Runs fine and charges fine otherwise. I hooked up the SW gauge as per instructions included with the new gauge.

I agree what I see is the battery charge when at 12.5 volts and surmise that it will destroy my battery over time. I took a pulley from a 35 amp alternator on an original dauntless engine to match up this this rebuilt alternator with my pulley set.

I do agree that 63 amps should be sufficient to power the fan, ignition and all lights. 63 amps is a good amount of current, unless something is faulty such as the regulator or maybe the windings are not up to the task at hand.

The regulator is solid state and is not old style with spings or available adjustments.

 

I will look to see if I have one. I doubt I do. Guess I could make one? Seems like a lot of effort. I do think the 63 amp model I have should cover the required current. I may need to do a bit of testing to see if there isn't another issue. Maybe battery is going bad, maybe fan motor has bad bearing, maybe regulator is not functioning properly. Could be that the alternator is overheating? Only happens when the absolute maximum current draw is occurring at minimum engine RPM.

A smaller pulley could alleviate this issue, but I am not sure the issue should exist at all.

 

I am reading about the 12SI alternator. It seems that the light wired in to the field circuit or a 50 OHM resistor or a diode is required if you wire it into the circuit on the starter switch that also powers the coil so that you can turn off the engine. Why not just wire it into the ACC side of the switch? Thats how I have wired my present charging system. No diodes, lights or resistors. Turns off with ignition switch and charges to 13.75~14 volts.

To me a light or another type of real resistor is no substitute for a diode to allow current only one way, as to not back feed the coil circuit and bypass the ignition run circuit. I am using a CJ5 ignition switch and have used an OHM meter to see where the start/batt/run and acc terminals are and wired accordingly.

 

Yeah, that makes sense. I have nothing like a radio or wench anything that I would need to use while engine is shut down. I wouldn't be surprised if one of the plates in the is battery are shorted. Its not new, was real cheap and has been just kicking around and not charged all winter. Its raining, so I am not inclined to check much right now.