Headlights dim momentarily when brake applied.
Thread Starter
Racer
Joined: Mar 2011
Posts: 337
Likes: 1
From: Mechanicsville Md
Headlights dim momentarily when brake applied.
Has anyone experieced their lights dimming momentarily when the brake is applied? I also notice it when the AC compressor kicks on. Is this normal or an indication?
Burning Brakes
Joined: May 2008
Posts: 1,106
Likes: 6
From: Georgetown Texas
Melting Slicks
Joined: May 2007
Posts: 2,072
Likes: 109
From: Longmont Co
Sounds to me like either the battery is going, or the cahrging system is not charging like it should. Or both. What does your voltmeter read, at idle and when cruising? Should show around 12-14. 10 or lower is a problem.
Team Owner
Joined: Jul 2006
Posts: 22,109
Likes: 4,137
From: Kannapolis NC
I've never seen one that didn't dim just a little when you touch the brakes. It's even worse when you hold up or down the power window switch when the window is already in the position you're requesting. You're wasting your money if you try to replace parts to fix it. If the battery is weak, it will get worse, but you'll notice things like the HUD resetting to default and DIC resetting to mileage (instead of wherever you left it) when you start the car.
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Advanced
Joined: Oct 2007
Posts: 89
Likes: 0
From: Cockeysville MD
Mine does this as well. Also does it when I put my windows up and then hit the buttons again to make sure they are all the way up before I shut the car off. Seems to be normal in my other cars as well.
Pro
Joined: Jun 2007
Posts: 681
Likes: 0
From: Flushed and swirling down the bowl
I noticed this awhile back. The best solution I found was to lower the load on the electrical system by switching out to LEDs. Those 4 big tail lamps are a big drain momentarily until the alternator can catch up.
Le Mans Master
Joined: Sep 2002
Posts: 6,569
Likes: 2,401
From: Redacted
Gents, my car had the exact same problem, and while I wasn't able to fix it completely, I was able to significantly reduce the amount the head lights dim when additional electrical load was placed on the car to the point that its barely noticeable. If you pop the hood, and look at both frame rails, just aft of the headlight doors, you'll see a gray plastic plug that attaches to a bolt on the frame. Those are the two frame grounds for the electrical system. I opened both of the plugs on mine and found massive amounts of sand along with a good amount of corrosion. I brushed out all of the sand, lightly hit the connections with a wire brush, packed it with dielectric grease and reconnected the plug on each side. The amount of dimming was significantly reduced afterwards. May not work for everyone, but it worked for me....Good luck
Le Mans Master
Joined: May 2006
Posts: 6,774
Likes: 361
From: Midland TX
That is the C5 (SPS) Slumber Prediction System kicking it. The Corvette assumes that when you hit the brakes that you no longer need its high-performance capability and it enters a "pre-sleep-mode" by closing its eyes. 
Navigator
Joined: Aug 2017
Posts: 9
Likes: 0
Car always starts no issues at all.
While testing I hit the brake about 10 times in a row and it caused a service traction, ABS, stability message and lights but upon restart the cleared and stored the codes as H.
When I turn the car off it goes basically flat and no floor lights turn on. The four accessory gauges also flicked.
also when I turn the car off the fuel mileage average MPG reset upon next reset upon next start I see the average mpg is reset.
Gonna swap in a new optima red top as I have this one under warranty 3rd year of this battery and it was also over charged by a bad deltran battery charger.
