Yeah it could just simply be a corroded ground at the block, battery, firewall etc. Loose connection.
That's why I asked about his alternator, but he wants dual alts instead of A/C.

 

well its not a huge problem. my lights dim just a bit and in my dash it was always at 14v and with the fans on it drops down just one bar. maby 13.5v. but i only have one fan hooked up. and if i were to hook up the other one then it would prolly go down even more. the original alt is fine its only a couple years old or so. the wires are fine. but from what you guys are telling me is that it will fry either the alt or the fan if hooked up directly. but what dont make sense is these alternators have their own rectifire bridge and voltage regulator. and it should only output the voltage needed to charge the battery. and if it dont see the battery then it will go to maximum output which is around 14-15v i think. but if i hook up the excitor wire to it then it should only output what is nessesary to charge the battery but its not going to the battery. correct me if im wrong. what do you guys think.

 

Go for it, If you want to hook your fans direct to the alt, Hey, good luck.

 

You could get your alternator field tested. One way of testing the diodes is to hook up a multimeter to the back of the alternator and then the positive of the battery. Set the meter to AC volts, and with the engine running measure the output. If the AC volts reads higher than 500mv then the diodes are shot.
I just did the AD244 upgrade on my truck. It works great and was very easy to install, needed a 1" longer belt. I got mine from an Stater/Alternator shop that rebuilds them.

 

i think im going to go ahead and try hooking up the second alternator and running my fans directly to the alternator but first through a relay. if it burns anything up it will be the alternator which i got for free or the 3 dollar relay.

 

Personally I'd call a shop that deals with alternators & ask - phone call is free.
If you want to "test the theory" it seems to me it could be a waste of a free alternator & not to mention the fans or any burned wiring that could cause a fire.

 

I really dont think it will hurt anything. i mean i know a guy who costum made his alternator to make it run power tools that took ac current. just hooked up a extention cord up to the back post on the alternator and ground. plugged his power tools in and got to work. so i seriously doubt that running a couple fans off of 12v dc would hurt anything. but i could be wrong. we will see when i get it hooked up. its been cold and raining here. ill get to work on it as soon as it clears up.

 

I just... aw never mind, No point in trying to say anything. we clearly do not know. LOL
Good luck.

 

alright guys. goter installed. check it out #!

but ive ran into one problem. the second alt is from like a 97 astro van with the 4.3l. and i cut the wiring harness to go with it. but it only has one wire which is the exciter wire. but my alternator in my blazer has 2 wires coming out of the harnes. a black and a red one. the black one matches up on the connector on my second alt with just the one wire.

so what is the pin out on the 94 s10 blazer alternators. which wire would i tap into for the exciter wire on the 97 alt?

 

wonder if it would be better just to run them on different circuits. like run a wire from the fuse box off a fuse that turns on when the key is turned on that way if the fuse blows for the one alternator you dont lose both

looks pretty good, like its almost factory