alternator question
Thread Starter
Burning Brakes
Joined: Jun 2000
Posts: 913
Likes: 17
From: Chatsworth, Ga.
alternator question
I replaced my old alternator this afternoon with a ZR-1 120 amp model. When I turn
on the lights at idle, the gauge reads 14.5 volts then jumps to 13.5 for a fraction of a
second, then to 14.3 volts. Old alternator was not charging and the voltage was
jumping from 14.2 to 12.1 volts all the time. I have not looked at the volt meter in a
long time, the only reason I was looking at it was because of the new APC headlights
I installed a couple of weeks ago.
Does the readings that I am now getting seem right?
I know this subject has been in here before, but when i did a search last night it only
found the one about changing the stock 105 amp to a 120 amp.
Thanks ahead of time.
Dan :confused:
on the lights at idle, the gauge reads 14.5 volts then jumps to 13.5 for a fraction of a
second, then to 14.3 volts. Old alternator was not charging and the voltage was
jumping from 14.2 to 12.1 volts all the time. I have not looked at the volt meter in a
long time, the only reason I was looking at it was because of the new APC headlights
I installed a couple of weeks ago.
Does the readings that I am now getting seem right?
I know this subject has been in here before, but when i did a search last night it only
found the one about changing the stock 105 amp to a 120 amp.
Thanks ahead of time.
Dan :confused:
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Re: alternator question (Danah92LT-1)
:cheers:
When you first start, voltage could run up to 14.5 but after a while should settle down to around 13.8
Lights on could drop it to 13.5
Jumping back and forth doesn't sound right
What's the frequency of the jumping?
:seeya
When you first start, voltage could run up to 14.5 but after a while should settle down to around 13.8
Lights on could drop it to 13.5
Jumping back and forth doesn't sound right
What's the frequency of the jumping?
:seeya
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: alternator question (Danah92LT-1)
What you observed is normal. The headlamps draw large current which decays rapidly as the filaments get to their operating temperature. The alternator voltage regulator cannot react this quick and your voltmeter will indicate this short duration drop and as the voltage regulator catches up with the new load, it will maintain 14.3 volts across the battery which your voltmeter will indicate.
Thread Starter
Burning Brakes
Joined: Jun 2000
Posts: 913
Likes: 17
From: Chatsworth, Ga.
Re: alternator question (Danah92LT-1)
Thank you both much. It was only jumping real fast on the old alternator. The new 120 amp one only drops for a fraction of a second and then goes right up to 14.3 volts with the hearlights on. I was just worried about how much current the new 130 watt APC headlights would draw. I also updated to the 886 fog lights at the same time.
Again thanks.
Dan :D
Again thanks.
Dan :D
Burning Brakes
Joined: Dec 2000
Posts: 1,161
Likes: 0
From: Orangeburg, NY
Re: alternator question (Danah92LT-1)
What you are experiencing is normal.The voltage can go as high as 14.7. What you described does occur during a draw or need for for amperage. The variations should reduce over time when the battery "gets used to the new alternator."
Safety Car
Joined: Dec 2000
Posts: 3,767
Likes: 5
From: Jacksonville Fl
Re: alternator question (Danah92LT-1)
Are you running the defroster? That runs the AC compressor on and off, which cycles the engine fan at the same time...all those with the headlights on will make voltage jump to a lower value than back.
It's normal.
It's normal.
Pro
Joined: Jul 2001
Posts: 652
Likes: 2
Re: alternator question (Danah92LT-1)
I posted earlier my problems with alternator replacement...
I replaced mine on my 92 with a 120A model, and it read 15.5 and a week later it burned out..seems like the bad battery killed its voltage regulator. Prior to that the bad alternator was reading from 14 to 12.8 , jumping like yours.
I have since replaced the battery and will install yet another alternator tomorrow and post the results...hope all works out for you.
I replaced mine on my 92 with a 120A model, and it read 15.5 and a week later it burned out..seems like the bad battery killed its voltage regulator. Prior to that the bad alternator was reading from 14 to 12.8 , jumping like yours.
I have since replaced the battery and will install yet another alternator tomorrow and post the results...hope all works out for you.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: alternator question (Danah92LT-1)
I was just worried about how much current the new 130 watt APC headlights would draw. Dan :D
[Modified by CFI-EFI, 4:28 PM 12/22/2001]
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