Low voltage
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Registered User
Joined: Jan 2008
Posts: 1,900
From: warren,michigan
Low voltage
I relocated my battery to the back of the car on my 94 z28.I used the correct gauge battery cables,I had the 140amp alternator tested off the car and it passed with no problems..I have a new optima red top battery,had it tested and it passed..Up at the alternator with my volt meter its putting out 14.1 volts,back at the battery with the volt meter I am getting 13.65 volts..My scanmaster is only reading 13.10 volts,also the stock volt meter in the car is reading 1/2 way..Does this sound like a bad ground problem?or do i need a bigger alternator?While driving the volts get no higher than 13.30..Any suggestions is appreciated..
Registered User
Joined: Jul 2002
Posts: 1,942
From: Kissimmee, Fl, USA
Re: Low voltage
I relocated my battery to the back of the car on my 94 z28.I used the correct gauge battery cables,I had the 140amp alternator tested off the car and it passed with no problems..I have a new optima red top battery,had it tested and it passed..Up at the alternator with my volt meter its putting out 14.1 volts,back at the battery with the volt meter I am getting 13.65 volts..My scanmaster is only reading 13.10 volts,also the stock volt meter in the car is reading 1/2 way..Does this sound like a bad ground problem?or do i need a bigger alternator?While driving the volts get no higher than 13.30..Any suggestions is appreciated..
Voltage drop is a function of length and resistance. If you keep the same gauge wire, you'll see lower voltage. Reduce the resistance by going to a smaller gauge number (larger diameter) wire and you'll see the voltage increase.
You're losing about a half volt in 15 feet which seems excessive...is anything getting warm to the touch?
I'm sure the engineers will chime in with ohm's law and wire gauge recommendations...
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Joined: Sep 2004
Posts: 0
Re: Low voltage
You have to follow the path of both positive AND negative. Take your voltmeter when the engine is running and first measure from the output terminal of the alternator to the engine block. Then move the negative meter lead to the frame of the front clip. You will probably notice a drop in voltage.
My suggestion is clean and possibly up the size of ground strap from the engine to the frame. At least clean both ends and be sure its tight.
Now because its a unibody, its relying on the body to carry the connection from the front to rear frame. I would put a clean connected strap from the front frame to the rear frame. Now be sure the battery negative terminal has a good clean connection to the rear frame.
Done.
My suggestion is clean and possibly up the size of ground strap from the engine to the frame. At least clean both ends and be sure its tight.
Now because its a unibody, its relying on the body to carry the connection from the front to rear frame. I would put a clean connected strap from the front frame to the rear frame. Now be sure the battery negative terminal has a good clean connection to the rear frame.
Done.
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From: Hell was full so they sent me to NJ
Thread Starter
Registered User
Joined: Jan 2008
Posts: 1,900
From: warren,michigan
Re: Low voltage
Thanks for the link Fred
....I used Accel lighting battery cable..I think i might have figured out the problem,my buddy grounded the negative cable to my nitrous bottle bracket inside the wheel well..I am going to get a longer cable and ground it to the frame rail,hope this takes care of the voltage drop..
....I used Accel lighting battery cable..I think i might have figured out the problem,my buddy grounded the negative cable to my nitrous bottle bracket inside the wheel well..I am going to get a longer cable and ground it to the frame rail,hope this takes care of the voltage drop..
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