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HVAC control knob lights stuck on "dim" - unreadable during the day

3K views 6 replies 4 participants last post by  plain OM 
#1 ·
This is on a Tribeca but some later Outbacks have lights on their HVAC control knobs and dimmer operating through the BIU or integrated center console controls, so thought i'd take a stab here.

the lights on the HVAC are stuck on "low" - like the setting you would have at night time. they are unreadable during the day.

they do not brighten when the lights are turned off.
the other interior lights do not have this issue - they work fine.

i was hoping to cut the wire and just power them directly, having them "always bright" but the problem is that they are digital displays on the face of the knob on the tribeca and actually read/say things - not just light up the knobs. So i'm not sure it's as simple as just powering it with a proper power supply.
 
#2 ·
I recall that the dimmer knob was a simple rheostat for 2005-2006 legacy (and maybe tribeca)

Then it became a controller for a PWM fader in the BIU when the legacy switched to LED panel illumination in 2007.

However, I think the basic bright/dim function as used by the HVAC portion of the display is just a make-or-break ground switch.
 
#3 ·
do you have a specific year? (for the vehicle / the stack that is in it?)

maybe someone like @plain OM would have some guidance.
 
#4 ·
I'm weak on electrical stuff - my understanding is the hard part here is it involves a digital display/read out and not just a simple light. So it needs to say things, interpret things, be a part of a processor somewhere - so I can't just power the light so to speak.

Dealer is probably the answer unless I somehow run across someone who knows this exact issue/system well.
 
#5 ·
I believe the radio and HVAC are integrated as with the Legacy/Outback auto-HVAC arrangement. In this case power, including for lighting, comes into the radio portion, and is then connected, internally, to the HVAC part of the control panel. If the radio control (knobs) lighting varies as it should when the brightness control is adjusted but the HVAC control and readout brightness does not, my first thought would be it's a problem within the integrated assembly.

There were cases here with the 3rd gen Outback integrated system where the controls, rather than not lighting properly as in your case, would freeze, so no radio changes and no control of the HVAC. The problem was apparently traced to bad solder joints on the main printed circuit board and bad connections between the board and the front panel where spring "fingers" are used to make the contact. Your symptom is not quite the same, but might be due to similar inter-connection problems if the radio illumination is working properly.

However, I'm not at all familiar with the Tribeca, and I haven't found a reliable wiring diagram, so I might be way off . . .
 
#6 ·
i think you're correct from my reading, the tribeca is integrated HVAC and radio as well - like a complete unit/assembly in that center console - all one unit. i saw mention of a Subaru Technical article mentioning both at the same time.
 
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