MaK_05TC

Being that this is my first post, i've done numerous research on how to fix this issue to no avail. Just so were up to speed on what's going on and what I have:

I purchased a 2005 Scion TC 5 speed manual with 200k miles. The car needed a new clutch and radiator hoses before being road worthy, so I purchased a Spec Stage 1 clutch, a set of SAMCO silicone radiator hoses and a Hotchkis front adjustable sway bar for icing on the cake. The stereo did not work when i picked the car up, but I left it as is for a few months to make sure the car was running tip-top. As of a few weeks, a new aftermarket stereo has been installed and the subwoofer/amp that was included in the purchase of the vehicle was finally wired up correctly. The previous owner's boyfriend wired this subwoofer and amp to the original deck and from what I read this can cause issues with the back-lighting on the gauge cluster.

Fast forward to where I am today, the gauge cluster back-lighting is the only malfunctioning issue with the car. All of the back-lighting on the climate controls, dome light and everything else work perfectly. The idiot lights also work, as well as the tripometer lighting. I checked both the under hood fuse box and the kick panel fuse box and both 7.5 amp and 10 amp fuse are in working order. So what gives? What could possibly cause the gauge back-lighting to not work? Is it a faulty gauge cluster all together? Perhaps the dimmer switch is broken? The vehicle does have an air bag light on, and i'm not too sure as to why? I've never really looked into this being the culprit. Could this be a safety issue that causes the lights on the gauge to turn off and make the idiot light more visible?

I know thousands of people have had this issue with 1st generation Scion TCs, so what was the solution?

Let me know,

Thanks,

-MaK

MaK_05TC

No one? lol

gjpjr84

I have never heard of installing a subwoofer, or anything related to the radio, doing anything to the gauge lighting.

the cluster is a self contained unit, if all the other lights are working then there is likely something wrong with the dimmer switch or board itself. if the dimmer switch was set to off, the HVAC backlighting would also be off when the lights were on.

MaK_05TC

First off, thanks for the reply.

Do you think this issue could be something as simple as the bulbs burned out? At this point, either way i'm pulling the cluster. I'd rather take one more step and check the bulbs in the back to make sure they're ok before looking into the idea of replacing the cluster.

What do you think?

gjpjr84

there are several LEDs soldered onto the board, replacing them isn't as easy as changing a bulb. it would be highly unlikely that they all died out together.

my guess is there is something wrong with the board or the dimmer switch, maybe there is a fuse on the board, i can't say i know what it could really be.

MaK_05TC

Interesting. I mean, the car has 210k miles. While this is nothing compared to my 233k 4Runner, it's just a bit of a pain with out any gauge cluster lights.

Is there a write up on how to fix the dimmer switch or is it basically a cluster replacement if it is truly broken?

gjpjr84

i'm not sure, you could try searching here and other scion tC forums to see if anyone has run into the issue, this would be the first i have come across this problem.

my only real suggestion would be to make sure the "panel" fuse under the dash isn't blown, but it sounds like you've already done that, and i would have figured the other lights on the dash would be out as well if it were out.

annoyingly, replacing the panel isn't the easiest either, you have to have the ODO info loaded onto the replacement, or else you'd could be in trouble if found out.

MaK_05TC

I appreciate the continuous response. I'm just attempting to get to the bottom of this.

Just so I understand, what exactly "lights up" as far as back lighting goes on the scion tc? Every single idiot light works, and the orange back lighting on the odometer/tripometer works perfectly. Moving down to the climate controls, the little lighting squares that tells you its "on" light up. Is there something more to the back lighting in that general area?

As mentioned before, I checked both the panel and gauge fuse underneath the steering wheel and under the hood. BOTH fuses appeared fine as far as the center link goes. But maybe they're still bad regardless? They looked original to the car and I did not replace them.

gjpjr84

searched for gauge or HVAC lighting

here is a thread about changing the LEDs
https://www.scionlife.com/forums/sci...od-com-129571/

and found pictures showing what all lights up on the dash, HVAC and radio

https://www.flickr.com/photos/teksty...955515/sizes/l
https://www.flickr.com/photos/teksty...130714/sizes/l

those show swapped LEDs, color is different but the lighting is the same, stock color is yellow/amber.

almost all of those lights are controlled by the dimmer switch when the running/headlights are switched to on, if the dimmer is turned all the way left it turns them all off.

the ODO is always lit and dims with the running/headlights switched on,
warning lights, and the small rectangles on the HVAC switches should always light up when activated.

MaK_05TC

After looking at the pictures you provided, the only lights that work on my scion are warning lights, odometer, clock and stereo (aftermarket)

My dimmer switch does absolutely nothing, so i'm assuming its an issue with that?

You wouldn't happen to know if there's a fuse on the actual panels themselves, would you?

gjpjr84

i don't know, sorry.

jkois

MaK,
You can find the wiring diagram in this post (#3) ---------------> https://www.scionlife.com/forums/sci...estion-233115/


Hope this might help out.


Make sure and grab the 2005 one, as things may have changed in the 2007 that I uploaded as well.