Bad voltage drop w/ new ho alt ?

[vic713 1]

I just got and installed my alt from DC.

First of all before w/ my stock alt I would idle at 13.8 and drop down to 12.4 at the most

So I figured the h.o. would help with that problem, I talked to Rob from DC, when I first bought the alt and he told me it would be a good idea to get a module, so I would charge at higher volts. Since I didn't have the money at the time. I didn't get it yet.

But anyways, I put the alt in; and I immediatly notice that I was idling really low. I checked it with Dmm and I was infact idling around 12.8. Now I know it would PROBABLY help if I add the module, but since I was already idling at 13.8, shouldn't adding the H.o. still keep me around that area ? I figured I would still be around 13.8 at idle but, it would just help with the voltage drop. But, thats not the case...

The pulley on the alt was alittle small, so I took that one off and put the factory pulley from the stock alt on it. It fits really good on it now, so I know its not from a loose belt, ect.

Yes I am going to call them tomorrow when their open but, I'm hoping to get some answers now.

Any input is appreciated.

[bassahaulic 155]

Put the one it came with back on.

Have you done Big 3?

[pear_b 1]

check your belt, might need a smaller belt.

[vic713 1]

check your belt, might need a smaller belt.

I put the pulley from my stock alt on to the h.o. for the purpose of it being alot better fit. I know thats not the problem.

Another thing thats funny is my batts rest at 13.1 and when I turn the car on they drop down to 12.8. Its not until I'm revved above 1k rpm's is when my voltage goes up to 13.5+.

Big 3 is done.

[vic713 1]

Could it be that my stock alt has some kind of voltage regulator built in. And the h.o. needs the module to charge properly ?

[vic713 1]

up............

[loondizie52 1]

what kind of truck do you have and what year, engine

[jonbearsmt 919]

some h/o 's charge less at idle....

was there a side diffrance in the OEM pully and the H/O pully?

i use a underdrive pully for mine.

[1200 bandit 2]

Is it a GMC car?

[shizzzon 461]

You guys arent seeing what he did.

PUT THE SMALLER PULLEY BACK ON.

The smaller pulley lowers the pulley ratio allowing the new alternator to start charging at idle.

Since you have removed it and put a larger one on it, the alternator is NOT ON. It's idle charge isn't being kicked in until at a later stage, anything over idle.

Pulling any current at the state it's in right now at idle is the same as doing it with the car off. Also, it's VERY bad to keep it like that because it's pulling lots of current out of the battery to keep the car running. I hope you aren't in a traffic jam anytime soon with that large pulley on there.

It's common to have to change belts when installing a high output alternator.

[bobonit 5]

You guys arent seeing what he did.

PUT THE SMALLER PULLEY BACK ON.

x2, put the pulley the alt came with back on and get a slightly smaller belt, otherwise you are doing nothing but asking for trouble.

Edited June 7, 2009 by bobonit

[vic713 1]

Ya, I got it fixed the other day. Put the smaller pulley on and got a smaller belt ( which was hard to find ).

Thanks anyways.

[vic713 1]

Car is a 5.2 Durango, for those who asked.