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Old Nov 22, 2018 | 09:40 PM
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Default Question about HUD wiring

Today was the first day I drove the car after installing a HUD unit. Everything worked fine in the garage yesterday. I played with all the buttons (up/down, bright/dim, mode, etc.) no problems. Tonight, however, I noticed when the headlights came on the HUD disappeared. I’ve searched & read this is not supposed to happen.
* edit: the HUD was actually on when I started driving tonight & the headlights were on. However, I started messing with the +/- buttons and then the display disappeared for the remainder of my drive home.

When I pulled in the garage, I turned off the lights and the HUD popped back up full brightness. I hit the - button & then noticed the + button did nothing & the display would not get brighter.

I also noticed the up/down arrows & Mode buttons are not illuminated with the lights on. Wondering if these symptoms are an issue with the wiring or with the projector/switch themselves? Thanks for any suggestions.

Last edited by JABCAT; Nov 22, 2018 at 11:03 PM.
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Old Nov 24, 2018 | 08:54 AM
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Get out the continuity meter and check connections. At night lights on or off the display should be very bright. Mine only gets washed out on light pavement during mid day. Shine your cell phone light directly at the photo sensor on the hud it should jack up the intensity to confirm sensor is working.
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Old Nov 24, 2018 | 02:13 PM
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Originally Posted by Dman302
Get out the continuity meter and check connections. At night lights on or off the display should be very bright. Mine only gets washed out on light pavement during mid day. Shine your cell phone light directly at the photo sensor on the hud it should jack up the intensity to confirm sensor is working.
Thanks for the reply - I’ll try that. Would a faulty switch cause these symptoms ( + button not increasing brightness) ?
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Old Nov 24, 2018 | 03:37 PM
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It’s hard to say without checking continuity to make sure that everything is getting the power that it should be. I had a wire pull out of the harness and couldn’t start the car… I damn near lost my mind, wiring has to be checked before you can go forward
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Old Nov 24, 2018 | 03:38 PM
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Also double check the wires you splice into to make sure you didn’t get a wrong colour
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Old Nov 24, 2018 | 04:15 PM
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Originally Posted by Dman302
Also double check the wires you splice into to make sure you didn’t get a wrong colour
Yeah - I haven't done one in a while now, but there is a gray and a brown wire in the dash harness that is commonly confused and the wrong one chosen. They're very close to the same color.

Last edited by BlindSpot; Nov 24, 2018 at 04:15 PM.
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Old Nov 24, 2018 | 11:44 PM
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Originally Posted by BlindSpot
Yeah - I haven't done one in a while now, but there is a gray and a brown wire in the dash harness that is commonly confused and the wrong one chosen. They're very close to the same color.
I double checked before putting everything back together & all the wires are correct. I checked it out fully the day before and all features worked. I buttoned it all up & then finally drove the car the next day (Thurs). Everything worked fine when I drove to dinner, I started getting issues when I drove home after dinner. That’s why I’m thinking maybe it’s the wiring, possibly something came loose?

Im out of town but will pull it apart and check the wiring on Tuesday when I get back.
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Old Nov 25, 2018 | 08:37 AM
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As mentioned I had a wire pull out of the harness and was a huge ordeal
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Old Nov 25, 2018 | 08:47 AM
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Originally Posted by Dman302
As mentioned I had a wire pull out of the harness and was a huge ordeal
this may be the case as a wire did pull out of the harness that plugs into the projector as I was splicing the wires together. I put it back in when got all the wires spliced and ready to go, but the custom wire harness I purchased was almost too short & I had a heck of a time trying to get the blue plug into the switch when I put the cluster back in because it just wasn’t long enough. I’m thinking tugging on the harnes to get the plug to clip into the switch could’ve maybe made that wire loose and after driving for a bit t came out?
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Old Nov 25, 2018 | 10:13 AM
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Mine was short too...wire pulled out and the whole damn car was in lockdown. I lost my mind thinking the gauge cluster got fried as whole thing was dead except the
mileage readout...
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Old Nov 25, 2018 | 09:46 PM
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Could be as simple as the button module connector not fully seated and clicked in. When I installed my hud, all was working until I got the cluster installed, then had nothing. Found that the connector on the projector was not fully plugged in.
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Old Nov 27, 2018 | 02:26 PM
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Pulled the cluster, checked all the wires & they all seem good. Everything works on the display except the + to increase brightness & the display disappears when the lights turn on?
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Old Nov 30, 2018 | 05:23 PM
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update: received a new switch and all buttons illuminate however, the HUD display still does not increase in brightness & disappears when the lights are turned on. Ideas on what to check next? Thanks!
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Old Nov 30, 2018 | 09:08 PM
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It does sound like a wiring issue, and quite possibly a short on that wire for the dimming, or a bad grounding wire from the harness.
It's tough to troubleshoot without being there.
I do have a PDF of the service manual section on Instrument /HUD that may help. It does show all the connectors, wiring etc and troubleshooting guides.
It may help you out. If you want it, PM me your e-mail and I'll send it to you. it's too large to insert in the post.

Good Luck
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Old Dec 1, 2018 | 07:29 AM
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Maybe I missed it above, does the cluster light up/dim correctly?
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Old Dec 1, 2018 | 09:02 AM
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Originally Posted by 87SAM
Maybe I missed it above, does the cluster light up/dim correctly?
Yes it does.
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Old Dec 1, 2018 | 11:23 AM
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Is there a way to monitor the voltage on the Instrument Panel Lamp Supply Voltage - 2 and the HUD dim down wires when the HUD is viewable and not viewable?
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Old Dec 1, 2018 | 11:56 AM
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Here’s something I noticed when messing with it last night. With the drivers door open the mirror lights were on. When I would press the up button on the HUD switch, the passenger side mirror light would dim?
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Old Dec 1, 2018 | 12:00 PM
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Originally Posted by 87SAM
Is there a way to monitor the voltage on the Instrument Panel Lamp Supply Voltage - 2 and the HUD dim down wires when the HUD is viewable and not viewable?
I can’t get it to be viewable anymore - maybe it’s the projector?
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Old Dec 1, 2018 | 12:11 PM
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Wow. Something up with the battery supply wire or ground? Maybe unplug the projector and see what the mirror light does
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