Battery or Alternator?
Thread Starter
Racer
Joined: Nov 2005
Posts: 417
Likes: 0
From: Cleveland TN
Battery or Alternator?
Just checking to see what you fellas think...
I've noticed that when I put on the brakes or something like that, it'll make the volts drop like 1 to 1.5 volts every time I put on the brakes..
Could I possibly have a bad battery or alternator?
I've noticed that when I put on the brakes or something like that, it'll make the volts drop like 1 to 1.5 volts every time I put on the brakes..
Could I possibly have a bad battery or alternator?
Burning Brakes
Joined: Nov 2004
Posts: 993
Likes: 0
From: PA
Not sure, but I'm under the impression that when the engine is running, the battery is under a 'float charge', so the voltage regulating alternator should be handling all electrical loads. If the battery has a bad cell, it MAY be causing the alternator to put out a ton of power, but that should manifest itself with higher than normal voltage on your DIC / IP, and a slight drop (1 - 1.5 vDC) would be noticable, but not the root cause.
When putting on the brakes, the engine RPM's drop, do you notice a drop in output voltage anytime the RPM's drop?
HTH,
Joe
When putting on the brakes, the engine RPM's drop, do you notice a drop in output voltage anytime the RPM's drop?
HTH,
Joe
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
You should measure the voltage at the output terminal of the alternator and at the battery terminals to see if there is a voltage drop between the two. You will normaly see the voltage drop a little when different loads are applied to the circuit.
The expert on alternators is Evil Twin! I know from many past post that if you get a rebuilt alternator from a run of the mill auto parts store, you may not get the correct one for your car! You may end up worse off than you were! NEVER give up your OEM alternator!!
If there is a problem with it, I recommend having it rebuilt rather than replacing it.
I will do a test on my 02 Z06 tonight and see what i get for a drop.
BC
The expert on alternators is Evil Twin! I know from many past post that if you get a rebuilt alternator from a run of the mill auto parts store, you may not get the correct one for your car! You may end up worse off than you were! NEVER give up your OEM alternator!!
If there is a problem with it, I recommend having it rebuilt rather than replacing it. I will do a test on my 02 Z06 tonight and see what i get for a drop.
BC
Le Mans Master
Joined: Sep 2002
Posts: 8,991
Likes: 2
From: Hanger 18 Taxachusetts
If you measure the battery with the car off it should measure 12v. If you have a dead cell it will be less. I think with the car running it should measure something like 14v. Have someone step on the brake while you measure the battery
Le Mans Master
Joined: Jul 2002
Posts: 7,370
Likes: 8
From: Slave to the evil empire
Cruise-In V Veteran
St. Jude Donor '04
This is normal, drive another car at night and you'll notice the same thing, sometimes at night when I'm driving my truck my headlights will dim when I take my foot off the gas.
The voltage regulator can only regulate the voltage so much, it will never be able to hold it exactly at a constant voltage.
The voltage regulator can only regulate the voltage so much, it will never be able to hold it exactly at a constant voltage.
Thread Starter
Racer
Joined: Nov 2005
Posts: 417
Likes: 0
From: Cleveland TN
I don't have anything to really test the battery or the alt. output with. I just look at the volt meter on the control panel thing (I'm not sure of the correct term of it. New-be here.)
I only really see a drop in the volts is when I either put on the brakes or kick the A/C on. When I turn on the AC, it drops over 2 volts then it jumps right back up to 14.2 volts.
The RPMs don't drop or anything like that when I do both the AC and the brakes. The volts just drop and they come right back up.
I only really see a drop in the volts is when I either put on the brakes or kick the A/C on. When I turn on the AC, it drops over 2 volts then it jumps right back up to 14.2 volts.
The RPMs don't drop or anything like that when I do both the AC and the brakes. The volts just drop and they come right back up.
Melting Slicks
Joined: Sep 2005
Posts: 2,066
Likes: 0
From: Crofton MD
Originally Posted by Blck00Vette
I don't have anything to really test the battery or the alt. output with. I just look at the volt meter on the control panel thing (I'm not sure of the correct term of it. New-be here.)
I only really see a drop in the volts is when I either put on the brakes or kick the A/C on. When I turn on the AC, it drops over 2 volts then it jumps right back up to 14.2 volts.
The RPMs don't drop or anything like that when I do both the AC and the brakes. The volts just drop and they come right back up.
I only really see a drop in the volts is when I either put on the brakes or kick the A/C on. When I turn on the AC, it drops over 2 volts then it jumps right back up to 14.2 volts.
The RPMs don't drop or anything like that when I do both the AC and the brakes. The volts just drop and they come right back up.
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Burning Brakes
Joined: Nov 2004
Posts: 993
Likes: 0
From: PA
Originally Posted by Blck00Vette
I don't have anything to really test the battery or the alt. output with. I just look at the volt meter on the control panel thing (I'm not sure of the correct term of it. New-be here.)
