I've read several posts about DIC control panel lights and dimmer/HUD switch lights staying illuminated at all times, but no one has replied with a solution. These are the only lights on. All others go out as they should. Apparently this is a fairly common issue as previous posts suggest. I'm tired of putting my C5 on the battery charger every night, and its frankly a lil embarrassing. AND no my switch is not turned on. Is there anyone out there who has fixed this problem??? Help me friends!!!!!

 

A friend of mine had a similar problem, only the HVAC lights would not turn off. I brought over a spare HVAC unit and we found out the problem was internal to the HVAC unit (not the BCM light control input) since the spare did not do it. We never bothered to try and find out what had failed in the HVAC unit. Something on one of the three boards (if I remember there are 3).

Your lights may be controlled via the IPC from the BCM. I say that since it is odd both the HUD and DIC lights stay lit. I will look at my FSM when I get home and see what I can find. You may end up having to pull the IPC and at least put in a "known good" DIC or HUD switch to see if that fixes that one, if not I would say it is something in the IPC motherboard that is bad like the HVAC unit I discussed above. I don't think it is the BCM at this point since the other lights dim. Will have to see if the BCM control to those goes thru the IPC or not with the schematics.

PS: Why don't you PM one or more of the Threads you saw to see if they found the problem and just did not post their fix ( I hate when people do that).

 

Man I didn't find any solution anywhere except for pulling the bulbs out. I just saw people posting the same problem. I'd think maybe the dimmer switch itself was bad allowing a little current to flow through,(since it is illuminated) or the headlight switch, or the headlight switch under the hood. I really hate to start throwing parts at it @ 100 to 300 dollars a guess!

 

I looked at the FSM which is not really much help at this level of detail. With that said, it certainly looks like the BCM signal to dim the lights is being correctly generated internal to the BCM since other lights dim. The dimming signal from the BCM goes to the IPC on one serial bus wire with all the other information the IPC needs so that path is working. From the schematics it appears the HUD and DIC lights are controlled together inside the IPC "envelope". Since the BCM dimming signal is sent on the serial bus my assessment is the motherboard in the IPC then dims the HUD and DIC in parallel. Short of pulling the bulbs out, I am back to the IPC as the issue. I think it very unlikely there is a dimming circuit in each of the HUD and DIC panels or that both panels decided to go out at the same time. However, if you want to get a good HUD or DIC switch to install and see if that fixes it for that side/switch it is still an option. Sorry all your options seem sucky but this is the best I can do at this time. The FSM falls really short in these find of issues. We would need some one who was on the IPC design team to help us.

You might try calling one of the IPC repair shops and see what they have to say, if they even know.

 

I appreciate the help friend. I'll tinker around with it a bit, hopefully find a fix and be able to share what I find.

 

I found this Thread on the same issue you have. Unfortunately if you look at post #20 he replaced the HUD switch and had no effect. This seems to support my opinion that it is the IPC.

http://forums.corvetteforum.com/c5-t...always-on.html

 

Thanks for jumping in and trying to help us find a solution for this problem. I followed your link here on my original thread right after I read your post. Sorry I didn't see it before.

I don't know if anybody has found a solution, but if someone did, it seems it has never been posted. I too came to the conclusion that it may be the IPC for the same reasons you mentioned. I can tell you for sure it is not the HUD or the DIC switches modules because I replaced them both.

In the mean time what I did to regain some normalcy was to install a remote switch connected in series with fuse 25 so I can interrupt power to the DIC's backlights after I turn off the car and re-establish it before turning the car on.

I know it is not a solution, just a workaround, so I'm really interested in getting to the bottom of this.

Have you guys found anything new?

 

I haven't yet. I cleared all my codes, charged battery, unhooked battery, beat on dash. I wonder if anyone with this problem also had a faulty ignition switch, or cranked up with a weak battery a few times? My car was acting a lil strange and did die on me twice without warning. Turned out to be a bad ignition switch. I replaced it and it was a miracle fix for all my crazy codes. Maybe cranking with low voltage can damage something?

 

I am still quite sure it is the IPC. The FSM is very lacking on this issue and does not even speak to the these switch lights that dim but lists every other one. As best I can determine the BCM sends the dimming request using the single serial bus wire to the IPC along with all the other info. If this is correct then we know the wiring and connectors are not an issue but the BCM request could still be corrupted. This would also support my idea that this dimming request goes through the IPC motherboard. As best as I can determine all other dimming requests are sent via different ways to all the other lights. I will try to speak to some IPC repair shops this week and see if they have ever seen this before.

I wish I could be of more help guys but I am at the mercy of lack of design information. All I can say is if it were me I would put in an IPC or replace the motherboard and test the theory. Your other option would be to have someone with a Tech II to verify the BCM is correctly outputting the demand signal.

 

I would agree that it's a failure inside the IPC. There will be an electronic circuit that controls the light level and it's likely failed.

I actually suspect it is the IPC which sends the light level information to the other modules via the serial bus. The dimmer switch goes to the IPC so it makes sense that the dimmer level signals all originate inside that module.

Just out of curiosity, do they dim or are they stuck at full brightness? I would expect the circuit has shorted and they're stuck at full brightness.

 

I'm under the impression that these specific lights are always fed +12v and it's the BCM the one that controls them through the IPC, which provides, or takes away, ground directly to that circuit with no relay involved (it's only a few miniature bulbs consuming just a few milliamps), but I haven't confirmed this.

If the BCM dimming request is the same for all lights that dim when the car is turned off and only these lights are ignoring it, that would probably mean the BCM is fine and the IPC is the culprit, but again, I don't know for sure if we are dealing with a single dimming request

 

Mine actually brighten when I turn the headlight switch on, dim a little when I shut the lights off and that's where they stay.

 

So they're at full brightness all the time. That still very much sounds like the dimmer circuit in the IPC has failed.

 

Did you have a chance to look around? Were you able to find anything?

Thanks again for your help!

 

I am so sorry, been side tracked on a bunch of issues. Thanks for the reminder. Here is a link to a repair shop I just called. He agreed the lights for the HUD and DIC switches ARE powered from the IPC. He said he could fix that for $120.

http://www.instrumentclusters.com/