Headlights dim
Thread Starter
Instructor
Joined: Dec 2012
Posts: 191
Likes: 23
From: Louisville KY
Headlights dim
Why would my headlights dim when I apply the brake or the base hits with the sub on? I realize it is a amp draw issue, surely the electrical system can tolerate this small of a fluctuation......
03 Z 11K miles, always garaged so the grounds should be in good shape.
Added, factory fog lights, and Euro taillights. Running an old Optima red top battery.
The condition occurs even with the sub off....
Any recommendations welcome
03 Z 11K miles, always garaged so the grounds should be in good shape.
Added, factory fog lights, and Euro taillights. Running an old Optima red top battery.
The condition occurs even with the sub off....
Any recommendations welcome
Melting Slicks
Joined: Mar 2004
Posts: 2,389
Likes: 405
From: Horseshoe Bend ID
Why would my headlights dim when I apply the brake or the base hits with the sub on? I realize it is a amp draw issue, surely the electrical system can tolerate this small of a fluctuation......
03 Z 11K miles, always garaged so the grounds should be in good shape.
Added, factory fog lights, and Euro taillights. Running an old Optima red top battery.
The condition occurs even with the sub off....
Any recommendations welcome
03 Z 11K miles, always garaged so the grounds should be in good shape.
Added, factory fog lights, and Euro taillights. Running an old Optima red top battery.
The condition occurs even with the sub off....
Any recommendations welcome
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
73Corvette - don't spread that info because the parts that describe the operation of the C5 have many errors. The PCM has no control over the alternator output voltage and the PCM doesn't tell the cluster the voltage over the serial bus.
Le Mans Master
Joined: Feb 2012
Posts: 6,644
Likes: 479
From: OK
Le Mans Master
Joined: Mar 2011
Posts: 6,835
Likes: 302
From: Columbia SC
What is the voltage AT the battery with the ignition OFF?
With the engine running what is the voltage AT the battery? After that, turn the HL lights on and let us know what it reads there then.
Mr. Sam
With the engine running what is the voltage AT the battery? After that, turn the HL lights on and let us know what it reads there then.
Mr. Sam
Safety Car
Joined: Mar 2015
Posts: 3,638
Likes: 245
Why would my headlights dim when I apply the brake or the base hits with the sub on? I realize it is a amp draw issue, surely the electrical system can tolerate this small of a fluctuation......
03 Z 11K miles, always garaged so the grounds should be in good shape.
Added, factory fog lights, and Euro taillights. Running an old Optima red top battery.
The condition occurs even with the sub off....
Any recommendations welcome
03 Z 11K miles, always garaged so the grounds should be in good shape.
Added, factory fog lights, and Euro taillights. Running an old Optima red top battery.
The condition occurs even with the sub off....
Any recommendations welcome
Thread Starter
Instructor
Joined: Dec 2012
Posts: 191
Likes: 23
From: Louisville KY
Voltage at battery with ignition off- 11.96 V
Voltage at battery with engine running- 14.6 V
Voltage at battery with engine running and lights on 14.4 V
Voltage at battery with engine running, lights on Stereo & Amp on Fluctuating form 12.3 V -14.2 V
Voltage at back of alternator with all on 14.1-14.5 V Fluctuating
You can noticeably watch all lights on the car dim with the amp on, same as when I apply the brake.
Thanks again for any help on this.
Joe J.
Instructor
Joined: Apr 2004
Posts: 133
Likes: 7
From: Wenatchee WA
Sorry for the slow reply, I've been in Europe for the last couple of weeks, now I'm back and have done the checks.
Voltage at battery with ignition off- 11.96 V
Voltage at battery with engine running- 14.6 V
Voltage at battery with engine running and lights on 14.4 V
Voltage at battery with engine running, lights on Stereo & Amp on Fluctuating form 12.3 V -14.2 V
Voltage at back of alternator with all on 14.1-14.5 V Fluctuating
You can noticeably watch all lights on the car dim with the amp on, same as when I apply the brake.
Thanks again for any help on this.
Joe J.
Voltage at battery with ignition off- 11.96 V
Voltage at battery with engine running- 14.6 V
Voltage at battery with engine running and lights on 14.4 V
Voltage at battery with engine running, lights on Stereo & Amp on Fluctuating form 12.3 V -14.2 V
Voltage at back of alternator with all on 14.1-14.5 V Fluctuating
You can noticeably watch all lights on the car dim with the amp on, same as when I apply the brake.
Thanks again for any help on this.
Joe J.
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Le Mans Master
Joined: Mar 2011
Posts: 6,835
Likes: 302
From: Columbia SC
I think your battery is the issue.
A fully charged battery should be 12.6v or more. It's not 12 volts it's 12.6 because each cell is 2.1 volts.
If the battery is
12.5 = 85% charged
12.4 = 65%
12.3 = 50%
12.2 = 35%
12.1 = drained