Alternator/Under Drive Pulley Concerns

777metalrb

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Ok so I know this is 5.0 specific but i didn't know where to put this question at. Anyways, my friends and I just got done putting in my new alternator and under drive pulleys. When I'm driving my battery gauge is red lined and my abs light comes on. I've already disconnected and reconnected the negative wire on my battery but nothing had changed. What's going on?
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Also am I safe to drive?
 

777metalrb

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I meant for the title to be "alternator and pulley questions" my bad
 

whiplash473

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I meant for the title to be "alternator and pulley questions" my bad
Fixed title.

Also, it's a little late now but those pulleys ain't helping none. I, unfortunately, don't know what the dealio is but just for your future reference - they're not all they're cracked up to be.
 

familytruckster

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I'd say your alternator is shit. Test the voltage and if it's more than 13-14 at idle get it off there before it fries something. Sounds like the regulator is bad.
 

ttocs

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it should be showing low voltage while idling. Throw a volt meter on it and see what it shows. I too do not recommend UDP's. They are hard on the alt.
 

CC'S95GT

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I'd say the regulator inside the alt is toast. Pull it off and have it tested.
Use a real multi meter and test the output voltage. It should be between 14-14.8vdc and should remain steady at idle through the rpm range.
As stated above UDP's offer no real HP increases other making the engine look pretty and you can do that with some spray paint and a couple hours.
 

ttocs

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with UDP's at idle you will probably be closer to the 12-13v range rather then the usual 14.5.
 

RichV

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I just fired up my race car for the 1st time since last October and with UDPs it makes 14.1V at idle.

The regulator inside the alternator makes sure the voltage output is 14-14.5V, if it's going higher the regulator is toast. IIRC you should be able to get one and just replace it. But if this is a new alternator, I'd send it back.
 

777metalrb

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Ok, I'll try everything and let y'all know all the info! Thanks for the replies!
 

777metalrb

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One last question, would putting my old alternator back on work? Nothing is wrong with the old one and I got the new one for the chrome finish. It was the first piece to my engine dress up. Also what I didn't mention before, my pulley set came with a crankshaft pulley and an alternator pulley. So I changed the pulley that came on my new alt to the under drive pulley. It's about .5 of an inch smaller. Would that make a difference as well?
 

familytruckster

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No reason it won't work if there wasn't anything wrong with it.

The pulley set shouldn't have had any effect on the alternator, other than possibly lower the output at idle. Not raise it.
 

ttocs

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I just fired up my race car for the 1st time since last October and with UDPs it makes 14.1V at idle.

The regulator inside the alternator makes sure the voltage output is 14-14.5V, if it's going higher the regulator is toast. IIRC you should be able to get one and just replace it. But if this is a new alternator, I'd send it back.

hey rich what do you have the idle set too? I can't say I hate them or that they do not have a place on anyones car but after smoking 2 alts in 3 yrs after installing mine I took them of. The problem really lies at idle as if you do not bump up the idle as most of them state then you will normally run closer to the 12v mark then the 14v mark. When that happens and the load or all the accessories it driving is not lowered the alt will build heat as a byproduct of being over taxed and underdriven. The other problem then lies with the fact that the alt is designed to cool itself while turning so fi that is slowed, it again helps it build heat. So with heat building and its inability to cool itself the way it was designed it just a formula for failue. So if you are not idling much as should be the case with a purpose built racecar its not so much of an issue. If you work downtown and are stuck in rush our daily both ways I would not recommend it. But I the end IMO the slight bump in hp while risking an alt or two down the road just isn't worth it normally imo. Its not one of those performance mods that you will feel in the seat after the install unless you notice that you wallet is lighter.

My advice on them if you want to try them is wait till you see a set for sale used and get them then. Be sue to keep your stock pullies in case you want to switch back and if you need or want too later you can. I paid $50 for my pullies and was able to sell them for $60 to help offset my alt losses. UDP's are not hard to find used from my exp hell all my friends sold theirs after replacing their alt.
 

RichV

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I fully agree with you Scott. The race car is not much tax on the charging system, no radio, HVAC, lights, or power accessories.

street car, specialy with some extracurricular stereo could kill the alternator easily.

Mine idles at around 1k. I have the BBK crank and pump pulley, but OEM alternator.
 

ttocs

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well now it depends on the racecar. I have a buddy putting a big block in his mustang and has it set up to run high to the tune of about 1400 expected hp. He had to add a 2nd battery because the starter needed so much juice and then take into account his big ass fuel pump and then charging both batteries and he can't run underdrives wit out having to charge it slightly between runs. I am actually giving him a HO alt that I just took off of mine in exchange for helping me/showing me how to pull and hopefully short install a motor so that it can keep up with both batteries.
 

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