My low beam headlights dont turn on at night. BUT...they turn on in the daytime almost always, except when the car has been driven a while????? I replaced the low beam relay, but no change. Any HELP? 2007 Corvette Coupe.

 

I have the exact same issue. It's been going on for a few weeks and driving me nuts. No sequence of shutdown or auto/manual on/off of low beams solves the problem. Seems as though they only work when the car is started in the morning and most of the day. At night all that works is the high beams, low beams just won't turn on automatically or manually.

2005 C6 with 100K.... first nutty electrical problem since new aside from the random service active handling message once or twice a year.

Thanks for any help that can be provided, I've searched the forums but only come up with the HID low beam bulb replacement and fog light upgrade posts.

Chris

 

Here are the TWO schematics that your going to need to resolve this issue. C6 uses the BCM to control a LOT more stuff than the C5. There are a few things that you can do to eliminate stuff. Make sure that all the fuses are good and check the BCM inputs and outputs.

My guess is something is telling the BCM that the LOW BEAMS do not need to be on. We just need to figure out what that is. If they work during the day, I doubt anything is wrong with the headlights then selves. More lime the the control circuit is corrupt. As much as I hate to ask you to do this, try disconnecting the battery and see if things change. Thats my last resort fix if you don't have a TECH 2 to test stuff and work the BCM remotely.







BC

 

Thanks Bill, I'm heading out to disconnect the battery now.

I'm not sure what you mean by checking BCM inputs and outputs. I'm assuming you mean checking the low beam realay (#47) switch.

 

The BCM is the ROUTER for all the input and output signals that control almost ALL the body functions. You need to check the outputs of the multifunction switch on the column and then make sure that all the other BCM inputs properly operating.

Are you seeing the signals at "A" and "C" when there suppose to be ON??

 

I haven't got that far yet...meaning into reading the BCM inputs. But with the multifunction switch on the column working as normal as in this morning on my way to coffee, I can't imagine that it would be the failure point. I am leaving it in the always on position for now and I'll see what happens later today when they typically start going out. Also, I forgot to mention that the car thinks the lights are on even when they are not, as indicated by the green "headlamps on" light on the dash being illuminated. It too goes on/off as I toggle the instrument column switch.

I also read your very informative post on the electrical issues with ground points. Great information and much appreciated. My car was purchased new in Oct 2004 and was an early vin car xxx4670 and has spent most of its life either by the beach in southern california or the damp SF bay area. 100K + miles and I'm sure some of those grounding points are corroded by now as well.

I'm going to try and replace the big block type relay (the 1.5" square one with 4 spade connectors in the front left of tray) and see if that solves the issue first. If that doesn't work I'll try my hand at the BCM stuff you mentioned.

Thanks

 

You can start with the normal headlight low beam function via the headlight switch.

The BCM has an internal pull up for it's digital inputs.
So with that pin high from the internal pull up it = OFF
Pulled low from a switch or relay to ground= ON

So if the headlight switch is turned on, PIn 15 on the BCM should be pulled low via the headlight switch to ground 201. If the parking lamps turn on then that ground is good, if neither the parking lamps and the headlights do not turn on, then you could take a jumper wire form pin K on the headlight switch to ground. If they turn on then you need to trace that ground connection. If they do not turn on and pin 15 on the BCM is low, then check pin C2-3 on the BCM for a low signal. This is what toggles the ground for the low beam relay. If you have any questions on this just let me know.

DJ

 

Thanks for the feedback. I had another member describe his heat damaged fuse block tray as the culprit for the low beams shutting off after a while. Sure enough I used an ice bag to cool the lid and when I restarted the car the low beams came on perfectly. After driving for 10 minutes I used a temp gun and the fuses were over 150 degrees when I first opened the lid.

I guess the internals are starting to get melted over time.... mine is an 05 which is driven daily.

 

Hmmmmmmm,,,,,, VERY INTERESTING! GM has had very POOR reliability with certain female connector pins. The C5 wheel speed sensor female pins are a very good example. They spread and loose contact with the male pin. Very common issue. Heres a good connector and a bad one:



The C5 Headlight multifunction connector has poor connections and gets very hot and melts the pin sockets in the connector. Same deal,, you loose the headlights.

Ive seen C5 fuses loose in the fuse box and either melt or have a pile of corrosion on the fuse blades..

The C5 ignition switch is another area of electrical trouble. The switch contacts arc and carbon up. Ive see the switch output a low as 8 VDC when the ignition is turned ON. Here is a result of the burnt contacts:





This issue with the C6 is something that needs to be noted and considered when electrical problems arise.

GREAT SLEUTHING and troubleshooting!! Well Done!


Bill C

 

I need to thank another forum member NO S8NT for passing on his contact number. We chatted over the phone for a few minutes this afternoon and I thought what the heck, I'll try his idea of placing a bag of ice on the fuse block lid... sure enough it worked. Then after using the temperature sensor on the actual fuses/relays I realized it all made perfect sense. They were baking inside a sealed box at 150+...

GM should warranty this stuff... What a total hazard for the low beams to shut off when driving. I'm calling them in the morning to raise hell and see what they say... my car is unmodified and driven in an average manner. 102,000 miles and original owner.

I realized something was amiss a week ago when an oncoming car started flashing his high beams at me on a quiet residential street in Atherton at dusk... then I saw a group of teens walking on the shoulder... if the other car didn't start flashing I wouldn't have started flashing my own high beams... not knowing my low beams were out.

I'm going to drill some small vent holes around the sides of the lid and see if that solves the issue... but I'm not sure if that area gets a lot of moisture or direct water spray when it's raining out. If that doesn't work I'll get a new entire fuse block... $453 retail... $269 on GMPartsdirect....

 

i finally went to the dealer. they replaced the whole fuse/relay box under the hood. they work fine now...

 

The dealer replaced the fuse/relay box under the hood. Lights work fine now.....

 

unfortunately my car is out of warranty... but I'll try.

 

Could be the light sensor itself is having issues but only a Tech2 will find it.

 

I too have this problem. I just hit 100,000 miles on my car as well...

 

This should be recall. No lights is a big safety problem.

 

I am a new member to the corvette forum.I have read the other members responses about the c6 low beam problem.I agree it's a heat problem.I live in the San Diego Ca. area and it can get a bit warm now and then.Now that it is getting cooler in the evening the lights work fine.I did buy a fuse block from GM Parts Direct.I am not going to put it in till I'm sure my fix works for sure.I bought some insulation Mid America Motorworks.Part No.104-002 and a roll of Aluminum Tape Part No.119-017.I measured the Fuse Block and made a template out of heavy brown paper.I them traced it onto the insulation.Cut it out and taped it into the shape of a box.It fit right down over the fuse block and keeps the engine heat away from the fuse block. Only time will tell. L Davis

 

This just started happening to my 2007 convertible over the weekend. Is there a service bulletin for this issue or is everyone just paying out of pocket if the car is out of warranty?

 

Check this thread and post...fairly simple fix that you might do yourself.

http://forums.corvetteforum.com/1582973586-post85.html

and the whole thread...very "illuminating"
http://forums.corvetteforum.com/c6-c...eadlights.html

 

Yikes!! All those sewage connections and combined with the fuse slip fit connections,, its a NO BRAINER that theres a heat issue.

I would make sure that the sewage connections for EACH fuse terminal is tight and you can also test EACH connection for the fuses/ Make sure that the fuse spade fit tight in each connection

Checking the connections with an OHM Meter to make sure that you have ZERO ohms is also a good preventative measure.

Bill