MPH light questions?
Thread Starter
Former Vendor
Joined: Nov 2005
Posts: 8,995
Likes: 2
From: Spring Texas
St. Jude Donor '08
MPH light questions?
I've noticed that while driving, the blue "MPH" light in the speedo will occasionally fade (but not go out copmletely) then light back up completely. Is this a strange kind of feature or is there an electrical problem?
Instructor
Joined: Jul 2007
Posts: 217
Likes: 4
From: Lafayette IN
...since you mentioned...at lunch today I was waiting in the car while my wife went into an office supply store and I noticed some momentary fading of the heater LED display and of the radio display (faded in/out in sequence)...I didn't think much about it, I looked at my volt meter while the engine was running and it seemed to hold steady...and I also looked at the digital read...I think it was around 13.8 or so volts...I know from past cars when the alternator is ready to retire, the headlights will dim / fade in and out of brightness....I'll assume a minor quirky thing.
Race Director
Joined: Jun 2005
Posts: 17,640
Likes: 1
From: Lenoir City TN
St. Jude Donor '08-'09-'10-'11
Yep same thing, shine a flashlight in the light sensor above the buttons to the right of the steering wheel (fuel, trip etc) you will see it change in intensity.
Team Owner
Joined: May 2006
Posts: 21,473
Likes: 356
From: Palmdale, Ca----- 2009 Cyber Gray 4LT A6 F55 452 RWHP 422 RWTQ- RIP 1998 C5 734 RWHP & 585 RWTQ-----
I've never experienced that or that I have noticed!
I'll check it out this weekend when I take it out for a run or two!
Thanks,Matt
I'll check it out this weekend when I take it out for a run or two!
Thanks,Matt
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Racer
Joined: Jul 2007
Posts: 469
Likes: 0
From: Salt Lake City Utah
I notice mine are dimmed at idle and on start up. I think what's happening is your alternator is only supplying a certain amount of juice with the belts turning slow. As soon as I start to move it lights up more, so I assume the belts are turning faster and supplying more power to the alternator. I also notice when entering the freeway that my radio gets louder slightly and I assume it's the same situation as the MPH light.
Let's hope this isn't a sign for us that our alternator is not working correctly!
Let's hope this isn't a sign for us that our alternator is not working correctly!
Safety Car
Joined: Nov 1999
Posts: 4,288
Likes: 1,161
From: Green and Wet Western Oregon
2023 C7 of the Year Winner - Unmodified
2018 C6 of Year Winner
That is not an alternator problem -it's Speed Controlled Volume (might not the correct name, but I don't want to go dig out my owners manual). You set the volume on your radio, but as your speed increases SCV adjusts the volume automatically.
Le Mans Master
Joined: Feb 2002
Posts: 6,937
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From: Waldorf MD
Race Director
Joined: Aug 2001
Posts: 10,783
Likes: 15
From: Hurricane Alley
If you will notice, its a lot brighter at night than it is during the day when the sun is out. Same thing if it gets overcast or your in the shade, etc.
Racer
Joined: Sep 2007
Posts: 314
Likes: 0
From: Las Vegas Nevada
