Alternator Upgrade Due To Electric Fan

GM ran 12 si alternators with fully computer controlled, twin fan with AC cars without a problem for years. If the draw outpaces 50 amps while cruising I would suggest that something else is amiss in the system. Or you are running a fan that is pulling crazy amounts of juice. I have run several Jeeps with 10si units with HEI and electric fans with no problems. I do pay attention to the draw of the fans however as some of them are power eating monsters.

 

Yeah, the one I have now is the predecessor to the SI alternators, a 10 DN unit. It is a reman with a new regulator... I got the battery load tested at the local auto zone and it tested ok. The new 12 SI unit should arrive Tuesday.

 

just ordered these diode/rectifiers to solder inline
Amazon.com: uxcell® 10 x 1N5408 1000V 3A Axial Lead Silicon Rectifier Diodes: Home & Kitchen

 

I don't think you suffer from having more power from your alternator. I installed a 105 amp Delco marine alternator in my 2A. Changed pulley to run with a standard flathead 3/4" belt.

 

Biggest improvement of the 12si over 10si is cooling. Design is better for continued high current loads. Should work well.

 

I found another diagram that might help. The blue wire just heads to key on hot.

 

The voltage sensing wire, the worst place tu put it it direct where the battery hook up to the alternator. Put it somewhere under the dash to get a better result.

 

Yes you can. But I've never found it nessisary. What he's talking about is the wire marked 2 on the alternator. Most people will just run it as the diagram shows directly to the charge wire. If the alternator output voltage seems to be loading down with lights and accessories on, then I might try running it farther away. In other words that wire senses voltage and tells the internal regulator to make more voltage if it drops below 13.8 volts. If you move the voltage sampling further down the line, the voltage will be slightly lower due to some resistive loss. So that will trick the regulator into thinking it needs to put out a higher voltage. This 12si is a vast improvement and I think, will hack the load just fine. Give it a try first. If there's still an issue we can figure something out.

 

I ordered the alternator and a new pigtail from rock auto. Was estimated to be here today, well it showed up Saturday while I was away. I have a front gate that locks and generally the delivery guys chuck it over the fence. I guess they left it out front. I live in a city. It is not around. Someone probably stole it. I contacted Rockauto and we shall see what happens next.

 

Sheesh can't a guy be sick anymore?

 

still no alternator nor reply from Fedex. Rockauto is awaiting Fedex response to them before sending me a new one. As you guys know, I live in a city and things happen. Cant get all worked up about it. Jeep is drivable as it is, just not at night.

 

Just a note from the peanut gallery. I've been running stock Motorola or Delco alternators for about 40 years and they have worked fine even with an electric winch. Back to my corner.

 

Do you have electric fan?

 

Yes, 11 amp draw when I turn it on. I still run the stock fan as well. It gets a bit warm out in the desert when I'm out there in the summer.

 

Finally got that 12SI alternator that got lost or stolen replaced and installed it. The pulley is smaller for the 12SI vs the 10DN. Its really straight forward for the install. There is a lug on the back of the 12 SI that is not on the 10DN, so you either need to reclock the case or get a longer belt and use the first hole on the adjuster, because it hits the alt mount. Whatever, its easy. I soldered in the diode. I really don't think you need it if you use the acc lug on the starter switch because when you turn the switch off it isolates everything on that side of the switch. I used the same wire I used for the same purpose on the external regulator and i didnt have a diode on that.... anyway

Started up the jeep, charges at at 14.53V or so at idle which is 650 or so with nothing on. Turn on the electric fan and its about 14, turn on fan and lights and its 13.7~13.6V. I didnt put on the brake lights, but you know that'll drop it under 13V for sure. If i blip the throttle to 750 or so, its back to 14+volts.

Its an improvement, but not ideal and I am not really satisfied. I dont know what to expect. Should I need to care?

 

Don't drive in the dark..............Nah should be fine!

 

Drove it around, got everything to temp. Lights on, fan on, brake lights on about 13.25 volts at idle, 13.65 without lights. Never goes below 13.25. Runs at 13.5 at cruising RPM. I guess success?

 

I just looked up the specs on a 14" fan set up as a puller like mine and it runs at about 17 amps. If set to push, it runs to 19.5 amps. Thats a huge amount of power consumption. If I had enough room I cannot see how an electric fan doesn't rob MORE power than a steel mechanical one at idle. I can hear the engine work when it kicks on. At cruising speed where you have little need for a fan, I can see the advantage though. Even if the fan is "running" while driving, it isn't pulling any amps as its being spun by the air being forced through it.

With all this is mind, a low speed jeep is better off with a mechanical fan if most of its life is spent in slow speed driving. JMO. The optimal fan would d be one with a clutch that has been done here before.

This is all assuming there is space for a mechanical fan, which I don't have. The next time I build a jeep I will place the engine or radiator so that there is enough room for a mechanical fan with a clutch.