MoePwr

iTrader: (2)

So when the car is running I check voltage using CDC on a voltmeter and it drops .2 volts a second just about. With the key in the on position the voltage doesn't drop. I just replaced the alternator. What else would cause this? What else should I check? Seems like the battery isn't recharging but I'm not sure. Please help me. I'm stumped

XLR8

iTrader: (52)

Have you added grounding straps?
Is the battery relocated?
Have you checked voltage at the fuse block under the hood or other parts of the system?
Do you have a PFC that you can monitor voltage at the ECU with?

MoePwr

iTrader: (2)

Battery is relocated to bin area. I haven't checked voltage at fuse block under hood. Which fuse block and what should I be getting? Car running or just in on position? Thank you

AzEKnightz

iTrader: (24)

When situations like this occur, I would simply ask myself these questions:

1) How old is the battery?
2) Have I recently drained the battery dry?
3) Is the car cranking slowly?
4) What's my voltage with engine running and engine off?

By asking these questions, you can basically eliminate if you have a bad battery or alternator.

With the engine running and battery voltage is dropping, you most likely have a bad battery. Because IF you check the battery voltage at the alternator putting out and it is constant that way you've narrowed down the cause. HOWEVER, if measuring voltage shows a constant voltage drop, you have a defective new alternator.

-AzEKnightz

MoePwr

iTrader: (2)

I'm using my battery from my daily driver that starts every time in my daily. Put it in the fd. Start it. Runs nice. Check voltage at the battery and its dropping rapidly. Check voltage at the alt and it holding a good voltage..... so how does your info help me with that....?

MoePwr

iTrader: (2)

I think its the wiring rather than the component but I don't know where to start. Sorry if I sound like a dick. I had my wisdom teeth removed and its killin me. Als excited because I'm trying to get her on the road

AzEKnightz

iTrader: (24)

I am about to say, you did sound like a dick in the post above. I was about to drop any help from you. However knowing you've gotten your wisdom teeth pulled, i've forgiven yah =).

So from my previous post, it would NOT help because you've already swapped a known good running battery.

Therefore, now everything lines within the wiring circuit.

A constant drop usually indicated a bad/loose ground or corrosion. I would double check your ground and the fuse block like another member suggested.

The fuse block would be the very front fuse block that holds the 150amp fuses where your battery positive wire is located to. Check for signs of corrosion and see if you find anything that might seem abnormal.

Keep us posted.

-AzEKnightz

AzEKnightz

iTrader: (24)

also, when you stated the voltage is dropping rapidly. Can you give us more detail on that? What voltage does it drop down to? Does it stayed there or simply ran down to let's say 11V?

-AzEKnightz

MoePwr

iTrader: (2)

It drops about .1 vdc per second if not faster. And my mouth is throbbing painfully. At the alternator it doesnt drop at all like where it does at the battery

MoePwr

iTrader: (2)

Where does the alternator ground at?

AzEKnightz

iTrader: (24)

for our FD alternators, or most alternator it's the core/shell that's the ground.

-AzEKnightz

MoePwr

iTrader: (2)

Sorry I am kind of a newb. You are asking me to check the voltage at the positive wire that's mounted on top of the fuse box correct?

AzEKnightz

iTrader: (24)

Yes, check the wire going to the fuse block on the side. It shouldnt be on the top unless it has been lay flat. Otherwise it should be facing the passenger side on the driver side. It should be the wire that's connected directly to the main fuse.

-AzEKnightz

AzEKnightz

iTrader: (24)

Also, if you dont mind me asking. How did you check your voltage drop at the battery with the car running? Because if you placed your ground wire from the DVOM to a bad ground, it can have this "voltage" drop issue you're stating. Not doubting you, but to reassure we are on the same page here.

-AzEKnightz

MoePwr

iTrader: (2)

got 12vdc at the alt and at that wire next to the 120 main

AzEKnightz

iTrader: (24)

so what other component do you have for the battery relocation? If there are no problem from alt to fuse block. And from fuse block to positive battery pose, either you have another component in the system that's causing this drop that we do not know about or you are placing your ground location checking the voltage drop wrong near the battery itself.

-AzEKnightz

MoePwr

iTrader: (2)

The voltage drops so low just from idleing that the 7 will actually die out on its own....

MoePwr

iTrader: (2)

I'm sorry if I'm asking the same questions but I just check the voltage by touching the pos and neg terminal in vdc correct? I may have gotten a bad alternator I just really need to be sure before I spend anymore money cause I'm seriously broke . Any input is very greatly appreciated. Thank you all

MoePwr

iTrader: (2)

Also is there anyway the Taurus alt will work on the fd? Saw the fcs have been using those or what is recommended?

BLACK MAMBA

iTrader: (58)

start the car and disconect the battery, if car dies out then there is something wrong with alt or wiring to the altenator.

also people might tell you not to do this because you could damage the ecu, and thats BS.


only disconect positive side of the battery terminal, and whatever you do dont let it touch any grounds.

MoePwr

iTrader: (2)

I thought you were supposed to do the neg wire? Well I'm curious as to where the voltage r egulator is. I unloomed all my wiring but I don't really see a problem anywhere