very strange problem with charging system cj5 v6

Hello, I have a cj-5 with a standard V6. The problem I have is with the charging system. The engine idles perfectly fine without running many accessories but when the electric fan turns on the engine will die if left at idle. If I have my stereo and headlights on it will idle even less amount of time and die. I thought it was an aging alternator or not enough output for the demanding electric fan. I replaced it with a high output single wire alternator and I have the same problem. I am confused as to what the problem could be. Also my battery charge gauge wont even give a reading 90% of the time. I have never seen anything like this. Any thoughts?

I also don’t understand why the battery never drains itself, I never have a problem cranking the engine. The battery doesn’t loose its charge, it just won’t idle

 

Ok, here's my guess.

If it always starts right back up without cranking over slowly or anything, it would make sense that battery isn't being drained. Assuming the battery isn't being drained, I'd say it's a problem somewhere else, not with the charging system. When you add more load to the alternator, it makes the engine work harder to spin it. Which is for some reason enough to kill the engine in this case. Does the jeep run good aside from this? How low is your idle set? Maybe check the timing, adjust the carb, check the fuel filter, general tune up stuff.

Is this a problem that just started or has it always been this way?

 

Check your grounds!

 

might look into a wider pulley for the alt as well.

 

I think a thorough check of the charging system is needed.
Remember that some of the high output alternators don't charge at idle; they have to be "excited" just off of idle speed before they will charge.
The problem might be solved by simply increasing your idle speed.

 

Thanks for all of the tips, and I have adjusted the idle many times to no avail, right now I lowered it to about 1,000 rpm (automatic trans =/). I have had the problem for quite some time. I mainly only have the problem when the electric fan is on.
The high load on the engine from spinning the alternator is a good idea, I never even thought of that. However is that very common? The engine doesn’t seem to have a problem though; the rpm's never fluxuate and never sputters. Normal maintenance stuff should be fine.
Looks like I need to delve into the wiring again.

You guys rock, thanks for all the input

 

Grounds are my first guess, often forgotten. Measure voltage drop at the coil when fan is kicked on (use frame as ground for meter) If the voltage falls below 6 to 4 volts you might have a run-ability issue, but I would think it would show up at higher RPM's due to need of voltage demand the more load is put on. But your Alternators output might mitigate volt loss at higher RPM's with higher amps. All of this is measurable at the coil during running of the engine. Grounds are needed as return path, check at the frame/eng grounds etc...Clean all connections as well as inspecting the heavy cables, any corrosion might add resistance. Your problems are voltage related if coil voltage drops off, but as I said look at the whole circuit not just the positive side. Hope this rambling makes some sort of sense.
Joe