Gauge Backlight Isn't Working and Parking Light

[kimokalihi]

My gauge lights are not working. I replaced them and a couple were blown but they still don't work. All the indicator lights work but not the backlighting of the cluster or the gauge needles. Also, the heater switch panel lighting is not working and the front left corner light does not work and that bulb was blown too but I replaced it and it still doesn't work. The right corner light works fine. Also the left passenger door has no power to the lock or the window.

I don't know if any of these things are related but it seems like they could be. The fuses are all good under the dash. I'm running out of ideas. I even checked voltage on all the bulbs on both sides of each bulb and they all have over 11volts (11.39ish) on both sides of each bulb on the gauge cluster. I don't understand how a bulb can have nearly 12 volts on both sides and not light up?

[Deride]

Maybe your dimmer switch on the column?

[kimokalihi]

I doubt it. Like I said that bulbs have what I imagine to be sufficient voltage which makes no sense at all.

If one bulb is out will it prevent the rest of them from coming on? Do you think the parking light, heater panel lighting and rear passenger door are related to the gauge backlight not working?

[Deride]

Maybe you forgot to hook a few wires back up on the steering column? I would check your illumination fuse under the dash, use the same spot to check if your dimmer switch is working (should only have power with headlights on) and no I don't think they are all related but the gauge cluster and hvac lights are. Also you can have a bulb out and the rest should work, only half my tleg cluster lights are working at the moment.

[kimokalihi]

Well that's good to know. I was thinking it wouldn't effect the whole cluster because there's several circuits on the back. Which can only mean it's got nothing to do with the cluster and everything to do with wiring somewhere. Which wires on the steering column need to be hooked up?

[Deride]

I'd start by following the headlight/dimmer/blinker arm wires back and see if you can find anything cut/disconnected.

[vrg3]

12 volts on both sides of a bulb means that there is no voltage across the bulb. What matters is the difference in voltage between the two sides of the bulb.

For a quick rudimentary overview of how this works, look at http://hyperphysics.phy-astr.gsu.edu/hb ... atcir.html

The way Subaru's dimmer system works is kind of the reverse of what most people expect. Each bulb has two wires going to it: a white one with a yellow stripe, and a yellow one with a blue stripe. The white-with-blue-stripe wire has +12v on it when the parking lights or headlights are on. The yellow-with-blue-stripe wire is controlled by the illumination control unit and varied between 0v and +12v. When it has 0 volts on it, the bulb has 12 across it, and it's at full brightness. When it has 12 volts on it, the bulb (having 12v on both sides) has 0 volts across it and doesn't light up.

So. Since you measure +12v on both sides of the bulb, we know the problem isn't the illumination relay or fuse.

So either Deride is right and it's the dimmer knob, or it's the illumination control unit itself.

[kimokalihi]

Aha. Very interesting. Where is the illumination control unit then?

[vrg3]

It's a little box mounted behind the console to the right of the stereo.

[Legacy777]

Here's a picture of the control unit

http://www.surrealmirage.com/subaru/fil ... tion05.jpg

[brweber352]

+1 on it probably being the illumination control module. I've burnt mine up before, by touching the ashtray light bulb wires together on accident. Easiest way I found to get to it was droping the glove box, then you should be able to see it. You can check to see if you got voltage going in it, and out of it. I didn't know how to use a DVOM when this happened, so I had to pay the dealer 1hr to tell me what I had already figured it was. The tech told me "voltage in, no voltage out, it's bad", I had to take his word on this.

Mine cost like $90 a couple years ago from a local dealer, you can probably get it cheaper online from a better source. You should probably try to find one at the junkyard. Just a tip, if you get it at the junkyard tell them it's a relay, if you say module they will charge you more.

Brian

[soobrdad02]

Wonder if I'm having the same issue. The dash, control panel, radio and side marker lights all dim when I hit the brakes at the same time I get an audible "click" from the shifter/ radio area. The headlights are unaffected. Sound familiar?

[kimokalihi]

I had no lights whatsoever. Never heard any clicking. Replaced the illumination module and they work now.

[07Evolved]

I believe this is happening to my cluster now. I had some bulbs out and I went in today to try and replace them.

The illumination on the cluster gradually started going out from right to left on the cluster. Every time I would connect/disconnect the wires to the back of the cluster, more illumination lights would be out.

I took a voltmeter to the back of the cluster and it seems that I am getting no juice only to the illumination bulbs.

I guess I should check the current on the illumination control unit? Is there anything else that I should check?

Just to make sure, the illumination bulbs are only the 2 green and 4 blue bulbs correct?

[07Evolved]

Forgot to add...all of the bulbs are blown now. So could this be the illumination unit or a fuse?

[kimokalihi]

I have no idea. There's a ton of bulbs back there that I replaced.

[07Evolved]

Whatever is happening, it kept blowing the bulbs. So I don't know whether it is the illumination fuse or the illumination unit. Is the illumination fuse in the panel underneath the dash?

[07Evolved]

I have no idea. There's a ton of bulbs back there that I replaced.

where did you get the bulbs?

[kimokalihi]

Autozone and National Auto Parts by my house. They're not an exact match but they work. Make sure you replace all of them. I don't think I had enough because autozone didn't have the right ones for some of them and the other place didn't have enough. So I think part of my cluster is now a bit dimmer than the rest.

[kimokalihi]

Whatever is happening, it kept blowing the bulbs. So I don't know whether it is the illumination fuse or the illumination unit. Is the illumination fuse in the panel underneath the dash?

If you remove the glovebox you can see two modules to the left of the glovebox bolted to the outside of the radio cage. One of those is the illumination module. Have you ever tampered with anything like wiring in a stereo or alarm, etc? That's how I blew my illumination module when I was wiring in my boost and AFR gauges without disconnecting the battery.

[07Evolved]

Whatever is happening, it kept blowing the bulbs. So I don't know whether it is the illumination fuse or the illumination unit. Is the illumination fuse in the panel underneath the dash?

If you remove the glovebox you can see two modules to the left of the glovebox bolted to the outside of the radio cage. One of those is the illumination module. Have you ever tampered with anything like wiring in a stereo or alarm, etc? That's how I blew my illumination module when I was wiring in my boost and AFR gauges without disconnecting the battery.

I have messed with wiring a stereo and such. Funny you should mention that, because I had to remove the boost gauge on top of my steering column to get the cluster out originally. I wonder if I fouled something up there and that caused the malfunction?

Ok, I will have to look for the illumination module. Is there also a separate illumination fuse as well?

[kimokalihi]

Yeah there's an illumination fuse in the driver's side kick panel area.

[07Evolved]

Ok, thank you very much Kimo. I will check it out tomorrow.

[kimokalihi]

Strange thing with the parking light. It randomly started working. I have no idea. I hate electronics in cars.

[07Evolved]

The illumination fuse is ok, so I am assuming it is a bad illumination control unit.

This may be a stupid question, but since I have a good working illumination control unit, could I swap in the "good" control unit into the car with the illumination not working to prove that it is definitely a bad control unit?

I just want to make sure that I could swap them to check and I wouldn't end up messing two of the units up.

Anything I should watch out for? Is this safe to do? Disconnect the battery when doing this swap?