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Okay finally tested this

1. They do get brighter when I turn the headlights off, then dim when i turn the headlights on.
Normal....

But is dependent on the setting of the dimmer. At the brightest dimmer setting, regardless of if your parking/head lamps are switched on or off, the interior control-surface/instrumentation illumination remains constant at the brightest setting. It's only from one click down (one level dimmer) that the dimming function actually goes into effect.

The control-surface/instrumentation illumination is designed in this manner so that the exterior lighting may still be engaged by the driver while at the same time still allowing for full cabin control-surface and instrumentation illumination.

Why?

For example, it's not always necessarily dimmer/darker when there's inclement weather. This allows the driver to really amp up exterior visibility for other driver while still maintaining the ability to clearly view the instrumentation and identify control surfaces.


2. but they still aren't readable during the daytime when it's sunny out - like not at all readable - not even a little bit.

3. the dimmer switch does nothing - all other lights dim or brighten - but the HVAC buttons do not.
Dimmer switch should vary the output of the climate control "rotaries" -


^ Image again taken from Cars101 2006 Tribeca photo page.

The readouts "inside" the "rotary" switches should dim/brighten in accord with the setting of the vehicle exterior lamps as well as the dimmer switch.

*** Can you verify:

A. that they should be readable during sunny daytime conditions? It seems like a given but I should ask.
I do not have a moonroof in my vehicle, but yes, even in bright daylight - through sunglasses, no less - the display should be easily readable.

B. the dimmer does or does not dim the HVAC displays?
The dimmer DOES (that's a positive/affirmation) dim the HVAC display pictured above.
 

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Discussion Starter #22
Great, thanks! Very cool info. So these definitely aren't working right.

The headlights do affect brightness (though still not readable)
Dimmer switch does not.

Sounds like maybe they're "stuck" on the lowest setting of the dimmer switch.

Does the dimmer switch have some kind of controller or should I be thinking it's still the entire panel that needs replaced?
 

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Discussion Starter #23
Installed another control panel - same thing still happening.

They do the same thing every day - bright at first start up. Then after 3 minutes (guessing) they dim to nearly unreadable (but they are lit a tiny amount). Other than that they're usually dim with very rare ocassions when they'll be bright.

There's no in between - it's bright or very very dim.

So - if i've swapped panels with the same result - now what?
 

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Discussion Starter #24
Just install a used control panel and be done with it.
I did that and no change???

I really wish I could just power them to always be on - this is rather silly to have a read out that it's not readable or diagnoseable.
 

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Frustrating Gary!

Sounds more like an issue with the dimmer switch than the panel then, eh?

Do all the other dimmer controlled lights work as expected (Instrument cluster)?

Seems like it is supply voltage but not the current necessary (thus the dimming over time as the capacitors in the system discharge). Or there is a large load that is pulling it down. Something you added that isn't factory? LED's installed in some place that shares this circuit? There is something labeled "Push Switch" that is tied to the same line that ties to the BIU 'dimmed' output.

Tough one...
 

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I am sorry the idea to swap the panel was incorrect. Sounded like an obvious thing to try in case a replacement unit could be located at low cost, especially because the FSM lacks schematics or troubleshooting information for these VFD indicators. I've spent some time trying to make sense of the wiring diagrams. We do know that the two wires for the illumination circuit are connected at the back of the radio (I85) and pass through to the connector for the control panel. If the red LED back-lighting still functions properly and replacing the panel fails to eliminate the problem, one is forced to conclude that the VFD brightness is controlled by some different means. What can it be? Maybe it's through the CAN data bus and/or the digital link between the control panel and the HVAC ECU. In that case, there also must be a special power supply circuit controlled by this input, but if so, it's safe to believe that it functions correctly (in both original and replacement units). The diagnostic table in the LAN communication section does say that "Illumination light is controlled with changing of data". If true, this cannot apply to all of the adjustable illumination, because everything visible on the diagrams is controlled in the old-fashioned Subaru way, through modulating the voltage on the negative side (even if the BIU now does the modulation).
Anyway, this still allows for a possibility that either the BIU or the HVAC ECU behind the glove box could be the culprits. I am in no position, however, to suggest that you should try replacing these.
 

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Since I no longer have the vehicle, I cannot check - nor sadly can I remember....

But does the Tribeca have an interior light-level sensor?

For example, with my '16 Outback, with the headlamps either in auto mode or engaged (or with the parking lamps engaged via the stalk) under daylight conditions, the display dims initially, but once it corroborates data from the interior light-level sensor, the displays brighten to full/daytime illumination.

If the vehicle is equipped with this sensor, a malfunctioning one definitely could be the culprit.
 

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Discussion Starter #32
Disconnect I85, the black square-looking plug on the head unit, and see if anything changes.
Thanks, I'll try that next.

I installed a third console (it was free) and it does the same thing. So seems unlikely it's the console.

The dimmer function works for the instrument cluster.

This is quite an eyeroll to make a light that you can't easily trace or repair.

I'm not finding any hits online, odd I have to run into an issue no one has ever seen before? I found one vague mention of an issue and repair but it was too ambiguous to know for sure they had the same symptoms.
 

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Our 06 actually has the same issue, where sometimes it works and others its nearly invisible or fades out I was planning to poke at it with my scope once I get home. However I won't be back to look at it for a few weeks as I'm out of town.
 

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looking at the schematics of the HU or the panel makes me dizzy, there are so much stuff there, since you said that dimmer does work, i guess the illumination circuit can be excluded, same for the panels as a replacement does the same,
my next move would be trying a different HU, as all the signals go thru it, if that doesnt work then BIU is where the problem is, now in reality it could be somewhere else entirely.
inside HU and Panel not much is serviceable you can replace pcb with other pieces but fixing anything on a particular pcb is way beyond my skills.

ps mine are not lit at all probably due to ribbon cables and i haven't had the time to look into it.
 

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Discussion Starter #35
my next move would be trying a different HU, as all the signals go thru it,
I installed another CD player/head unit and no change.

I'll check the ribbons and wiring to the area next.

Since you've peaked at the wiring would you mind commenting on whether it would be possible for the dimmer to work - but it still cause that lighting display not to work? Or if the dimmer works then that automatically rules out that the dimmer is the issue?

I'm tempted to replace that stalk/dimmer switch but at the same time I think I would almost bet money that's not going to fix it.
 

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The HVAC control unit mounted to the side of the blower housing also has a CAN connection, like the head unit. Just to mention a remote possibility of it being at fault. Not very likely though, if the rest of the data stream between the HVAC ECU and the control panel is still good. According to the pin-out posted above, CAN connection is through B1, B14 and communication with the panel (unidentified protocol) is through B18, B19.
 

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Since you've peaked at the wiring would you mind commenting on whether it would be possible for the dimmer to work - but it still cause that lighting display not to work? Or if the dimmer works then that automatically rules out that the dimmer is the issue?
totally possible my dimmer works perfectly and i have no lights in the displays at all, all functions work otherwise. my issue is homemade longer ribbon cables or that i took cd changer off HU. Haven't looked at it yet.
 

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I also have the same problem you describe. Mine is an 06 as well, starts working fine when you first start, then after 5 minutes or so, dims to the lowest setting, sometimes comes back on its own too, but other than the lighting issue with the 3 displays, works perfectly in all other functions. I have not had a chance to really diagnose anything with it, currently over yonder in an ugly, hot sandy place, but will be back soon to look at it again soon. Where are you located? I might be of assistance with troubleshooting the problem
 

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Discussion Starter #39
I also have the same problem you describe. Mine is an 06 as well, starts working fine when you first start, then after 5 minutes or so, dims to the lowest setting, sometimes comes back on its own too, but other than the lighting issue with the 3 displays, works perfectly in all other functions. I have not had a chance to really diagnose anything with it, currently over yonder in an ugly, hot sandy place, but will be back soon to look at it again soon. Where are you located? I might be of assistance with troubleshooting the problem
Did you get around to fixing this?

I still haven't looked into mind, indeed I don't really know what to do. 3 panels all did the same thing and they worked fine in other Tribeca's after i installed them on mine, so the panels are fine.
 

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Discussion Starter #40
I'm still in the same boat:

3 entire center panels and 2 or 3 other stereos (which afterwards worked on other vehicles) didn't' change anything.

I'm going to ask Subaru if they could actually diagnosis it when I stop in there next week, but my guess is they'll just charge $100's for diagnosis and installing $100's more in parts that don't fix it. I can nearly guarantee they would have tried the items i've already replaced.
 
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