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1999 Corvette Coupe HUD display is too dim to see in daylight. It is OK at night or in the dark garage. I have previously had a C5 and a C6 with HUD, so I believe my expectations for this one are in line with what Chevrolet intended. The brightness control is turned all the way up. I have Twilight Sentinel and Automatic Headlamp Control disabled in the DIC because I don't like the headlights popping up when I drive into the garage. That should confirm that the light sensor/photo-transistor works correctly. I have searched the forums and can't find any solution to the problem. Help!
It took me a while to get back to this problem, but here is what I learned:
There is a photo-transistor in the HUD unit. I disassembled the HUD and determined that the photo-transistor was defective. A bit of solder across the two leads to the transistor makes the circuit think it is in bright sunlight all of the time. Now I can see the display in daylight. If it is too bright at night the HUD dimmer slider can resolve that problem.
The 1st picture shows the location of the photo-transistor.
The 2nd picture shows the small circuit board that the photo-transistor is mounted on.
The 3rd picture shows the reverse side of the circuit board and the two points (lower right corner) that I bridged with solder to trick the circuit into thinking it was in bright light.
The 4th picture shows that the display works in daylight now. Hurray!!!
While I had it apart, I cleaned both mirrors and replaced the clear acrylic top window that had a crack in it.
Try pulling the HUD off of the IPC and examining the small connector that fits into the IPC connector for the HUD. Make sure all of the male and female pins are clean and the female pins have a nice tight electrical connection. Do a pin push / pull test to ensure that the female pins are not spread apart inside the IPC.
While you have the HUD off, I would open it and make sure all of the internal connections are clean and tight.
It took me a while to get back to this problem, but here is what I learned:
There is a photo-transistor in the HUD unit. I disassembled the HUD and determined that the photo-transistor was defective. A bit of solder across the two leads to the transistor makes the circuit think it is in bright sunlight all of the time. Now I can see the display in daylight. If it is too bright at night the HUD dimmer slider can resolve that problem.
The 1st picture shows the location of the photo-transistor.
The 2nd picture shows the small circuit board that the photo-transistor is mounted on.
The 3rd picture shows the reverse side of the circuit board and the two points (lower right corner) that I bridged with solder to trick the circuit into thinking it was in bright light.
The 4th picture shows that the display works in daylight now. Hurray!!!
While I had it apart, I cleaned both mirrors and replaced the clear acrylic top window that had a crack in it.
Great idea "Dirt" But, while this seems like a good quick temporary fix I'm no too sure shorting out the optos leads is a great long tern idea. This could lead to an over heating issue and case even more damage to the circuit board at best. At worse I think it could cause a fire. Why not just replace the optotransistor while you have the HUD apart? Just wondeng
Great idea "Dirt" But, while this seems like a good quick temporary fix I'm no too sure shorting out the optos leads is a great long tern idea. This could lead to an over heating issue and case even more damage to the circuit board at best. At worse I think it could cause a fire. Why not just replace the optotransistor while you have the HUD apart? Just wondeng
This won't cause an overheating issue. The "shorting out" here doesn't mean shorting out power to ground, which would draw a lot of current and is what I think you're thinking. The sensor here provides a voltage reference signal; shorting it out just tricks the HUD into thinking there is a constant light level, at which point you can use adjust the brightness manually. Given the difficulty in finding a replacement photo sensor, this is the route I would go as well. The only downside is having to adjust the brightness between daytime and nighttime, if that really bothers you. As a reference, others have done this as well:
Will "shorting" the photo resistor wirk on my C6 like on a C5?
I have heard they are similar... both C5 and C6 have 2 wires that go to the photo resistor but the C6 has 3 solder points where the C5 has 2. Looking more closely at the C6 photo resistor, two of the points eventually go to the same trace on the circuit board. Which do I solder together? Does it matter? Will it work with the C6? Thanks!
Originally Posted by CheapSpeed
This won't cause an overheating issue. The "shorting out" here doesn't mean shorting out power to ground, which would draw a lot of current and is what I think you're thinking. The sensor here provides a voltage reference signal; shorting it out just tricks the HUD into thinking there is a constant light level, at which point you can use adjust the brightness manually. Given the difficulty in finding a replacement photo sensor, this is the route I would go as well. The only downside is having to adjust the brightness between daytime and nighttime, if that really bothers you. As a reference, others have done this as well: https://www.youtube.com/watch?v=uHS1KHxCQRI
I have heard they are similar... both C5 and C6 have 2 wires that go to the photo resistor but the C6 has 3 solder points where the C5 has 2. Looking more closely at the C6 photo resistor, two of the points eventually go to the same trace on the circuit board. Which do I solder together? Does it matter? Will it work with the C6? Thanks!
I haven't worked on a C6 HUD, but if the two points end up going to the same place, it sounds like it wouldn't matter. If you have a multimeter, you could test for continuity by testing the resistance between those two points that go to the same trace.
figured. I did it when I retrofit it. I know the gears have all been fixed in my hud from the guy I bought it from her but it’s tough to see in daylight. I do not have the hud windshield. If I wear sunglasses with the top down I can’t see it, so it sounds like thus hack would work.
HUD too dim
And again thanks for the follow up. 
