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Old 07-23-2012, 03:17 PM   #1
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Voltage drops

Hello everyone. Well I'm new here to this and well I have a question that seems to bug a lot of people. My volt gauge drops at idle. I have tried many things and still no luck. I upgraded they alt to 130-150 amp. I changed all battery cables to solenoid. Power and ground. I installed bigger gauge wire on three ground cable on driver front fender. I do have underprice pullies but deleted smog pump and switch to electric fan. Car seems to be fine with out any accessories on. Soon I start turning on a/c and headlights it starts to drop. At night while driving I'm only getting about 13v. I checked with aftermarket guage. If anyone out there has fixed this issue I would love to know. Thanks
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Old 07-23-2012, 03:23 PM   #2
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Do you have hid's on the car?

---------- Post added at 03:23 PM ---------- Previous post was at 03:22 PM ----------

Do they brighten when you idle it up some and the voltage go up?
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Old 07-23-2012, 03:25 PM   #3
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Yes I have hid and no they don't dim down. This would happened before hid install
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Old 07-23-2012, 09:13 PM   #4
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Re: Voltage drops

"My volt gauge drops at idle." is your clue.
Replace the UD alternator pulley with a factory diameter pulley.
IMO, UD pulleys cause more problems than they are worth.
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Old 07-23-2012, 09:41 PM   #5
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I forgot to mention that I already installed a stock pully only on the alt thinking it would help but still no luck. The thing is with a/c at night on high and lights on while driving I'm right u set 13v. The guage moves as I turn the a/c blower to slower speeds the gauge starts to move back up at each different speed.
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Old 07-23-2012, 09:52 PM   #6
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Perhaps because the fan is drawing more amps to increase speed.. Idk that's a good one mine doesn't do that at all..l
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Old 07-23-2012, 09:58 PM   #7
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Re: Voltage drops

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Originally Posted by 88stang5.0 View Post
I forgot to mention that I already installed a stock pully only on the alt thinking it would help but still no luck. The thing is with a/c at night on high and lights on while driving I'm right u set 13v. The guage moves as I turn the a/c blower to slower speeds the gauge starts to move back up at each different speed.
Sounds like you might be close to maxing out the 130 amp alternator or you may have some grounding, wiring or motor issues.

Also, if you used a UD crank pulley I would replace it with stock too.
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Old 07-24-2012, 10:38 PM   #8
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Excuse my Ignorance but how would a smaller crank pulley cause the issue would t it spin faster since it smaller?
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Old 07-24-2012, 11:01 PM   #9
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I actually have an overdrive pulley for mine
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Old 07-25-2012, 12:09 AM   #10
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Yep spins faster and makes voltage higher
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Old 07-25-2012, 12:30 AM   #11
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Re: Voltage drops

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Excuse my Ignorance but how would a smaller crank pulley cause the issue would t it spin faster since it smaller?
Yes, but UD pulleys are designed to slow the accessories down (Under - Drive) , so the crank pulley would likely be larger not smaller.
If you had a smaller pulley it would be an Over - Drive pulley.


I said UD because if it came with a set of UD pulleys that is what most people are going to call them, saying OD would likely cause confusion too.
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Old 07-25-2012, 11:52 AM   #12
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Re: Voltage drops

I had a UD crank pulley and switched it out with the stock circumference one and my voltage problems went away.
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Old 07-25-2012, 02:59 PM   #13
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Re: Voltage drops

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I had a UD crank pulley and switched it out with the stock circumference one and my voltage problems went away.
There we go, living proof.
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Old 07-25-2012, 03:02 PM   #14
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Quote:
Originally Posted by Trojan Horse

There we go, living proof.
Yeah, I've played those games to. These cars just don't react good to UD pulleys.
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Old 07-25-2012, 03:10 PM   #15
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Re: Voltage drops

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Yeah, I've played those games to. These cars just don't react good to UD pulleys.
Nope, I have a set of nice aluminum ones in the garage somewhere, that I should sell, but I can't honestly pawn them off on someone else knowing the issues they cause.


Converting to an electric cooling fan will net you around the same HP increase that the pulleys are supposed to provide. Of course you would still need to upgrade the alternator for that too.
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Old 07-25-2012, 03:24 PM   #16
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Quote:
Originally Posted by Trojan Horse

Nope, I have a set of nice aluminum ones in the garage somewhere, that I should sell, but I can't honestly pawn them off on someone else knowing the issues they cause.

Converting to an electric cooling fan will net you around the same HP increase that the pulleys are supposed to provide. Of course you would still need to upgrade the alternator for that too.
I feel like the parts suppliers should have some kind of warnings on them when they sell them. It seems like I must have seen tons of threads where people have had these issues. Then people try to put back just the alternator pulley back on, and still doesn't fix. This is because they don't realize the crank pulley is still making it spin slower.

Anyone else reading this. Please don't buy UD pulleys. Lol
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Old 07-25-2012, 08:15 PM   #17
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Well I can't seem to remember where I left my stock pulleys. Guess I have some digging to do in my attic and garage. Keep you guys posted on what happens when I do find them and installed. Hopefully by this weekend.
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Old 07-26-2012, 11:49 AM   #18
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Re: Voltage drops

I/m just curious on how low your volts were dropping because when I had the voltage problem I didn't use an electric fan and it got pretty low.
Please excuse the dirty screen, that stuff won't come off.
It would start from this and go to the other after driving for awhile.
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Old 07-26-2012, 01:43 PM   #19
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When I get home from work today I'll post some pics of where it at and when I have everything running. Gets pretty low and while driving with everything on I get shout 13.5
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Old 07-26-2012, 11:04 PM   #20
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Here are some pictures I took tonight as I drove home. The first one is at idle with no lights on or a/c. Second one is Driving nothing one. Third is driving with a/c. Fourth one is with a/c and light. And last two are at idle with a/c on and lights on.
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Old 07-27-2012, 05:51 AM   #21
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Re: Voltage drops

Wow, down to 11, i guess the fans draw way too much power to be running with the UD pulleys. Does it start up fine?
BTW I like that volt gauge.
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Old 07-27-2012, 09:29 AM   #22
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Re: Voltage drops

That's exactly why I won't use UD pulleys.

Since I plan on having numerous electrical components I bought a PA Performance 200 Amp alternator. It will produce up to 100 Amps of power at idle, so issues like you are showing there don't happen.
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