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Discussion Starter #1
Working on a 2012 Outback H6 without sunroof. Some years ago I replaced all the bulbs with LED arrays with no issues until, when driving at night a week or so ago for the first time, the map lights glow very dimly. The dash indicator works; the lamps & room lamp & key ring all dim properly together, but the map lamps stay dim, like a feedback issue. Key ring and room lamp go out completely.

Replaced map lights with the original bulbs which now go out completely.

When pushing the individual map light switchs in slightly, I can cause the opposite LED to go out completely just before the controlled lamp goes full bright (when the switch is between contacts I presume).

Any suggestions/comments/checks?

TIA
 

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Any suggestions/comments/checks?
What happens when one of the two LED map lights is removed. Does the remaining one glow brighter, or go off completely?

Also, what happens if the Door-Off switch is set to Off? Do the LEDs continue to glow, or go out.

Have you tried replacing both LEDs with new ones?

Some aftermarket LED bulbs have caused issues when used in areas designed for incandescents.

I'd replace the LEDs with new, and see if the glowing continues. If they do, then that might mean there's a fault (leakage to ground) in the wiring between the bulb switch and the BIU, or a defective BIU.

2012 map lights.jpg
 

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Discussion Starter #3
What happens when one of the two LED map lights is removed. Does the remaining one glow brighter, or go off completely?

Remaining one glows slightly brighter.

Also, what happens if the Door-Off switch is set to Off? Do the LEDs continue to glow, or go out.

LEDs continue to glow.

Have you tried replacing both LEDs with new ones?

Yes. Symptoms were the same.

Some aftermarket LED bulbs have caused issues when used in areas designed for incandescents.

I'd replace the LEDs with new, and see if the glowing continues. If they do, then that might mean there's a fault (leakage to ground) in the wiring between the bulb switch and the BIU, or a defective BIU.

View attachment 471130
 

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Also, what happens if the Door-Off switch is set to Off? Do the LEDs continue to glow, or go out.
LEDs continue to glow.
With the DOOR-OFF switch at off, the wiring to the BIU is not involved. For the LEDs to continue to glow, there has to be some sort of leakage path to ground in the switch/map light area.

Both individual map light switches are Off?

A leak from a sunroof is not an uncommon cause of electrical problems up in that area, but the car doesn't have one, right? Any other water leaks, perhaps around the windshield?

Probably going to require more detailed troubleshooting, perhaps including taking down the map light assembly to inspect the switch.

Do you have, and are you comfortable using, a digital multimeter?
 

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Discussion Starter #5 (Edited)
Okay, this thing is possessed. So I'm going back and forth; changing bulbs, switching switches, pulled the whole thing off the headliner, measured resistance both sides on/off, etc. Put it back up, put the incandescent bulbs in, and headed off to get a bite to eat. The whole dashboard lit up with warning lamps. Now I've got an UltraGauge on it, so I cleared the faults and came back. After having read in some other threads about common grounds on the OBD & the BIU I got to thinking. I cleaned the posts on the battery. The battery is about 2 months old and I cleaned the posts when I installed it.

Ta-Da

All better now. No glowing LEDs.
So, kiddies, don't overlook the obvious. Start at the beginning.

Thanks for the input.
 

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Okay, this thing is possessed. So I'm going back and forth; changing bulbs, switching switches, pulled the whole thing off the headliner, measured resistance both sides on/off, etc. Put it back up, put the incandescent bulbs in, and headed off to get a bite to eat. The whole dashboard lit up with warning lamps. Now I've got an UltraGauge on it, so I cleared the faults and came back. After having read in some other threads about common grounds on the OBD & the BIU I got to thinking. I cleaned the posts on the battery. The battery is about 2 months old and I cleaned the posts when I installed it. . . .
When the map light DOOR-OFF switch is set to Off, and the individual map light switches are Off as well, the low side of the two bulbs don't connect to anything (see attached). Basic electrical theory would say the lights can't (normally) be on, or even glow, because there's no path for current through them. They would be totally independent of the ground circuit.

If I understand correctly, after the latest bulb changing, measuring etc, the incandescent bulbs were installed, not the LEDs. Earlier it was reported that the incandescents didn't exhibit any glow when they were first re-installed, and I presume they didn't when you headed off to eat. Is it possible that during the more recent measuring etc., something was moved/changed/corrected so that had the LEDs been installed immediately after, they too would not have glowed? In other words, the battery connector aspect might have been related to the warning lights coming on, but I tend to doubt it would have been involved with the LED map lights glowing.

But then, the car might indeed be possessed!
 

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Discussion Starter #7
Your inquiry line of reasoning is exactly what prompted my possessed comment. It doesn't make any sense to me, particularly with the room light acting totally normally the whole time. Unless there is an internal semi-short in the map light assembly/plug/harness that is feeding just enough current to make the LEDs glow.
 

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. . .It doesn't make any sense to me, particularly with the room light acting totally normally the whole time.
Not really. Note on the wiring diagram (post #6 above) that the room light and the map lights both go to the BIU, but to different terminals. The BIU controls the lights (on, dim, fade off). With different terminals, and possibly separate drive circuits to each inside the BIU, it's quite possible for the door light and map lights to work, or fail, individually.

{quote]Unless there is an internal semi-short in the map light assembly/plug/harness that is feeding just enough current to make the LEDs glow.[/QUOTE]

That's what I was trying to determine by having the DOOR-Off switch and the two individual map light switches, turned Off. If the glow continued (as it apparently did) then the "semi-short" would have to be in the map light assembly, between the low side of the bulbs and a ground, as shown by the blue line in this diagram:
471181


The semi-short has to be in that area -- if it were in the harness going to the switch, the low side of the bulbs would be isolated by the open switches, and so would not be affected.

The LEDs probably require only a few milliamps, if that, to just barely glow; it wouldn't take much of a "short" to provide an adequately conductive path to the ground for that.

Interesting . . .
 

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Yup. I think you're on to something. While the two map lights do glow when both are plugged in, they act slightly differently in reaction to unplugging the other bulb and attaching the multimeter probe. If memory serves, the left goes completely dark when the right side is played with but the right will brighten/darken when the left is played with.
 

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Yup. I think you're on to something. While the two map lights do glow when both are plugged in, they act slightly differently in reaction to unplugging the other bulb and attaching the multimeter probe. If memory serves, the left goes completely dark when the right side is played with but the right will brighten/darken when the left is played with.
I don't have access to one of the 4th Gen., assemblies to have a closer look. This is a photo of the back of a 2006 map light assembly (with sunroof control). The two areas circled in blue are the map light switches (disregard the red arrows).

471193

[From this post]

Interesting that instead of wires, it uses metal straps between connection points. This 2006 system is simpler than your; the map light switches are spst, simple on/off, whereas your's are spdt, where the switch selects between connecting to ground, or to the connection to the BIU. But I wonder if your's uses the same metal strap connecting system.

In the 06 photo, I can see areas where the low side of the bulbs could be connected to ground through a "semi-short" bridging between the two straps at the back of the switches. Accumulated "conductive dirt" is a possibility, and it might "disappear" (e.g., fall away) when the assembly is taken down from the roof.
 

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Discussion Starter #11
Verrrrrrrrrry interesting!
The 2012 is similar but the switches are enclosed for the most part. I'll have to pull it back out and see if I can get the switches apart without destroying them.
Stay tuned.
 

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Interesting. It has regular wires instead of the "straps".

In light of that, it's more likely the glowing was caused by a fault at one of the two map light switches. As one of the three switch terminals (where the wires are connected) is a ground, a fault inside either switch, or across the terminals on the outside of a switch, could cause the symptoms.

I guess now that the LEDs aren't glowing this is somewhat academic, but it might be useful if the fault reappears.
 

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Discussion Starter #14
I pulled the assembly out this morning and partially disassembled it. By pushing down on the little locating tabs on the covers to the left & right of the switches the covers will come off. It makes it easier to pull the switch off by unscrewing the tiny phillips screw that you can't see in the above pic and rocking the switch out. I then squirted the switches with some CRC contact cleaner then blew them out and reassembled. Hopefully this is all it will take to return to normalcy.

Thanks again.
 
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