tapply4894

Yeah mine does the same thing with the head lights.

engifineer

That is the common 07 hvac issue that this thread is about Unless you messed up something in the dimmer wiring then I would guess that you should check for this issue on the board.

SilentSeraph

Alright, so I took it all apart, fount T303 and T304, both seemed to be connected fine. Neither would budge with minor applied force. Took a magnifying glass to take a closer look and they are connected. Im having the same issues with everyone else, 07 TC w/aftermarket pioneer deck, the HVAC lights turn off when headlights turn on. I notice when I apply force near the "off" for the air conditioner the HVAC lights up and will sometimes say on. Does anyone have any other suggestion?

johnnyr888

Thanks for simple instructions and relatively easy fix!

ScionOfLife

So my just purchased 2007 tC, which I researched so carefully has the HVAC Lighting issue. I even spent time reviewing forums for issue, but failed to spot this (Didn't know to search for it till I had the car/issue!

So ALL the lights on the buttons are out on the HVAC face, and only the LCD display lights/goes out with headlights or parking lights on. I have not seen this particular flavor of the issue before, most have all the lights on or all off. The only lights I ever see are on the HVAC LCD display. The buttons never light. The fact that the display light it toggles on/off with headlights looks like classic t302 solder points, but why then al the button lights out, do I have additional issues to deal with? Does anyone have a spare circuit board so that when I pull it apart, if it's more than just the t302, I would not have to do this twice? I could pay a bit for the board if I need it. Ugh. this is really putting a damper on the new ownership experience, especially since the LED Third/High Brake Light strip is also dead - got the dealer willing to replace that if needed anyway.

As I reread the thread - my symptoms very closely match this:

LEDmod

Just do the solder properly and you shouldn't have issues with them...

For the TBL, just buy aftermarket TBL with full extended LED
If you just bougte the car recently dealer should replace that for you.. since that light is required light to be functional to be on the road...

ScionOfLife

Yeah, I got all the way to my second day of ownership before getting hit with 3, count' em 3 known or common issues. The dealer is gonna have to take the hit on the TBL, since he gave it a passing inspection. Don't think he wants the DOT coming around wondering why he is passing cars with lights that don;t work, LOL!

So, TBL, HVAC lights, and here's a biggie: No master keys. None, just a Valet key... this sucks. I got a dealer here in Raleigh that will reseed either the ECU or immobilizer (can only be done a single time, but my odds are good as this was a single owner car) and he will code it to a new master and include the Valet in the coding for $90. Not too terrible, now if I can just find a master blank for a decent price. eBay had an OEM one for $175, and aftermarkets for $42. Do I trust the non-OEM ones, or what?

mc1114

New 07 TC owner here, having the same issue. Tried to do the solder trick but did not work

From everything stated above, it seems 05-06 units are not compatible with 07, which might explain why, when I swapped units with an 06 (good working unit), neither car had working HVAC controls, although the physical connection at the back was the same

However, Scion OEM parts sites list the same part number for 05-07 (55911-21020), and on Ebay the listings are for used units that will fit 05-07

Anyone have some insight? I'd really like to get this fixed with a used unit. For a lack of a better term, it sucks being unable to see the controls at night. lol

mc1114

So 08 will work with 07 but 05-06 will not. Found a used unit from a 08, without being sure if it was compatible. Turns out it is. Only thing is the colors at night are slightly different compared to the gauges and radio, but thats just minor. So glad to have this fixed finally

kfox112

Good evening,

I recently purchased a 2007 Scion TC to learn how to drive a manual transmission. I do love it so far. I noticed though that when I turn on my headlights, my clock backlight turns off - ergo why I found this thread.

I attempted the fix in the original post with much difficulty since my soldering iron tip is not nearly as small as this tiny T302 transistor. To my amazement, it worked when I tested with just the board. On go the headlights, the clock stayed lit, and an array of new LEDs that I'd never seen before (presumably to keep buttons illuminated at night) kicked on too. I was so happy... at least until I put everything back together and it stopped working again.

Taking the screws back out didn't fix the issue, so I retried the solder reflow fix with success two more times, and had the same problem both times - re-installing the screws that hold the circuit board to the plastic back put me back at square one.

On my fourth attempt, I ended up breaking the transistor off of the board. And now - it only has two legs instead of three. The leg on the single side is broken off. Even though I'm transistorless, everything works exactly as it had before - no backlight when the headlights are on, but the clock illuminates when the headlights are off.

So I'm left wondering - do I have any options at this point other than buying a new board? Is a transistor "done" once a leg falls off... or with the right size (tiny) soldering iron, could you potentially solder a leg back on?

Thanks for the help,
-Kyle