Subaru Outback Forums banner

81 - 100 of 131 Posts

·
Registered
Joined
·
106 Posts
A couple more data points

Hi all,

Put me on the pile of folks grateful to the OP - thank you deccher! I have a couple of additional (useful?) comments:

- I've owned my car for three years and the middle light ("Pass airbag") has _never_ worked (I didn't even know there was a light there!) BUT I didn't get the dash "airbag" warning light until a few weeks ago (yes it was proper Canada cold, but it's not the first winter I've been through with this car).
- The dash "airbag" light came on intermittently even after the soldering job. The issue only fully cleared up after a couple of trips with someone actually _sitting_ in the passenger seat.

I love this forum! :)
 

·
Registered
Joined
·
12 Posts
Thanks

I've been having the intermittent "Airbag" light during the winter on so I gave your fix a try. I checked the resistance of the resistors and they were good. The solder connection for the four LEDs looked aged and discolored. So I touched them up with my iron and now there a nice shiny silver. I didn't have the nerve to touch the other connections since they were very small.. Anyhoo, reinstalled the panel and connections and the dash light comes on for 5-10 seconds, then off. All of the LEDs come during the initialization, and then the Pass Off is lit. Time will tell if one of the LED connections was the culprit.
Thanks for the detailed instructions, Tim
 

·
Registered
Joined
·
54 Posts
I've had my '06 Outback for a month now. Love it! It has happened twice that the air bag light was on (not the one by the mirror, the warning light near the tach). Both times with a passenger. Next time it was started, no light. These glitches were a couple weeks apart. Is/could my issues be related to what is discussed here?
 

·
Registered
Joined
·
30 Posts
Sorry if I'm resurrecting an old thread but I found this through a google search. I bought a 2006 outback recently and had the airbag light on intermittently. While waiting for a family member at the doctors I found this and took apart the overhead console. I did not see any really bad joints but many of them looked like cold solder joints. I couldn't do anything at the time so I connected everything back together and now the pass. airbag indicator functions correctly and displays on or off... and the airbag light is now off. I will be pulling the console back down and reflowing all of the solder.
 

·
Registered
Joined
·
54 Posts
I've heard burned out map lights can cause problems with the air bag circuit as well. Both my map lights are good.
I got busy this last month or so, and the warning light didn't go on for a few weeks. Did it three times last few days. I will try solder re-flow fix this week.
I did note the passenger air bag indicators after the recent glitches. Just now neither the on or off light was lit, but the red air bag light by the tach wasn't on.
 

·
Registered
Joined
·
54 Posts
I just did this fix, with adjustments. The solder joints for the LED's look crappy (like they were soldered "cold"), so I redid them. The resistors looked like they had good connections, so I left them as not to take a chance on overheating them. By chance I put the assembly on a white piece of paper and noticed the inside of the passenger map light was blackened, indicating it was starting to go. I replaced that as well.
So far, I've driven it a few times without air bag light problems. Time will tell if this was the fix. It's been doing it almost every time I drove it the past few days, so there is reason to think it's resolved.
 

·
Registered
Joined
·
1 Posts
Airbag overhead circuit board

I have a 2006 Subaru Outback Wagon and had the exact same problem. I re soldered the circuit board
and that solved the problem. It looked to me that over time the solder connections on the resistors
crystallize and crack from the vibration of the vehicle. Great info.

Thanks Guys
 

·
Registered
Joined
·
83 Posts
Airbag light started to appear couple of weeks ago. Would go on sporadically, this thread help narrow down the problem area that is only a millimeter wide. Saved time and $$$! Thanks!
Solder had dried and cracked. Red circle indicates where. Just tinned the end of the iron and pressed against it to reflow. That's it! done!
 

Attachments

·
Registered
Joined
·
139 Posts
Fixed this today, off/on for passenger side flickered all winter (console), then airbag light started to come on. On the board two connections were noticeably cracked on one end when examined with magnifying glass. Tiniest tab to re-solder the two and all appears good as passenger sensor working again and airbag light is off. thanks again
 

·
Registered
Joined
·
672 Posts
I wish the fix was this easy for the '05, but it isn't... it's a different setup. Looks like I'll have to get a new sensor for the seat, or try to get mine recalibrated at the dealer. Since odds are the dealer will charge, it looks like I'll live with it. I can't believe there isn't a recall on this, since other companies have been hit with mandated recalls for similar issues.
 

·
Registered
Joined
·
1 Posts
This presentation "2006 OBW - Airbag Light On - My fix" was the best I found to help me get the 2009 Legacy dash airbag fault repaired. I fretted over trying this 're-flow' suggestion, because my unsteady hands aren't much for soldering tiny spots. My passenger airbag OFF light occasionally came On as it should, and the dash AIRBAG light would reset, then maybe in 24 hrs, the light didn't light up for the Passenger Bag Off condition. And the Passenger ON light responded anytime I had a passenger.
After about 6 months it seemed as if it often was related to temp or humidity changes that the Passenger Bag Off light would not light, so I accepted the notion, it was possibly, for me, the solder issue. In the middle of the process, I decided not to unwrap the plastic glued around the connectors, so I ended up doing the work sitting in the front seat, with connections intact. All went as planned and I didn't break anything, but I managed to overheat the tube insulation around the harness wiring. So that is something you may want consider; I could have heated the wires together in the bundle. I wish I had thought like others to check for cracks with magnifying glass. I just finished, but so far it started working, repeatedly, correctly. This is why I love the internet and people who utilize it, to share their findings and their questions. Thanks for offering me a way to cure this annoying problem!
 

·
Registered
Joined
·
1 Posts
Hello all! I had the EXACT issue and just now fixed it. Hairline crack in the black square solder joint. I, however, was too lazy to find the soldering iron in the shed. So instead I just used a pencil and rubbed the graphite over the cracked joints. Worked like a CHARM! Not sure as to the longevity of this fix but at least now I know what's wrong so if it stops working again, I'll dig out the soldering iron and do it proper. For now though, this is working perfect and I can see it lasting quite awhile. So to any future readers who aren't confident with soldering like the previous comment, you can try a pencil to get by!

THANK YOU to the original poster for figuring this simple fix out!!
 

·
Registered
Joined
·
2 Posts
Same issue here...a faulty airbag PC board leading to the intermittent illumination of the airbag warning indicator. Thanks for identifying the problem and solution, deccher.

Based on the information in this thread and high magnification analysis of my own airbag PC board (see photos below), it appears a likely cause of the solder cracking is expansion cycling or mechanical stress. On the expansion cycling side, this would be thermal (and perhaps, in some cases, hygroscopic) cycling of materials that have different expansion coefficients. The coefficient of thermal expansion (CTE) of ceramic surface mount components can differ significantly from the CTE of the laminated PC board on which the components are mounted. The larger the CTE differential and the larger the physical size of the component, the greater the expansion difference, and thus the greater the force exerted on the solder joint. On the mechanical stress side, the overhead map light module may be susceptible to physical forces due to driver or passenger operation.

Exploring thermal expansion further, surface mount cracks due to CTE differences often show up after many repeated thermal cycles: sometimes after as little as 500 or fewer cycles, but often after 3,000 or more cycles. The fact that something like this can show up after a great deal of cycling seems counterintuitive: it's more intuitive to surmise that cracks form from a sudden, high-impact force. Nonetheless, crack formation due to cycling differential expansion is well documented in the surface mount engineering literature.

If I were to summarize this issue, it would be as follows:

1) The root cause of this type of airbag warning light failure is due improper specification by Subaru engineers of materials/components used in the airbag warning PCB.

2) The possible primary contributory causes include:
a) use of direct-mounted surface mount components that have coefficients of thermal expansion that significantly differ from that of the PC board on which they are mounted;
b) use of larger size surface mount components, wherein the CTE effects are greater (note, however, that the resistors will be specified to meet current/power requirements and to mitigate against power related risks); and
c) design of an assembly module and housing potentially susceptible to physical/mechanical stresses.

3) Other (and less likely to be substantiated by this forum) contributory causes include:
a) use of solder that can not sufficiently withstand expansion cycling (most, if not all, solders are susceptible, but some formulations are less susceptible...for instance certain types of lead free solders can be more prone to cracking under cyclic stress, and certain solder manufacturers (Koki, for one) produce solders specifically intended to help counteract this problem);
b) inadequate soldering practices (note, however, expansion cycling can cause solder joints to appear as if they are cold solder joints, according to one NASA whitepaper on the subject).

While cold solder joints may first appear, during visual inspection of the PCB, to be present and a root cause, this is probably not actually the case in the majority of PCBs, though cold solder joints, when present, can accelerate the effects of expansion cycling.

Potential manufacturing engineering solutions:
1) Use components specifically formulated to withstand, counteract, or minimize the stresses of expansion cycling. A number of manufacturers make such components;
2) use PC boards and board layer materials specifically formulated to match that of the components to be mounted on them. A number of manufacturers make such materials and boards;
3) reduce the size of surface mount components, where allowable by power requirements, or switch to through hole components configured with bodies and leads that can withstand cyclic stress; and/or
4) design the assembly to better withstand physical/mechanical forces so as not to transfer stresses to the PCB.

It's likely that Subaru had implemented some form of risk mitigation, during the design phase, for this type of failure, but it seems if so the mitigation strategy is insufficient for these model years (2006? - 2009?).

Rewetting all solder joints or rewetting them with a less stress-prone solder will solve the problem for a period of time. That's the prescription I followed. However, it won't necessarily guarantee the problem won't recur over the long haul, especially if the car is located in a region that has greater and more frequent temperature and humidity variations or the assembly is otherwise subjected to mechanical stresses.

Apologies for the long-winded post.
 

Attachments

·
Registered
Joined
·
18 Posts
Not sure how I even stumbled on this thread, but 15 minutes with the soldering iron last night finally solved the airbag light problem on my 07 OBW! The OP deserves an award and this should be a sticky. I began with re-flowing the solder joints on the LEDs which did not fix the problem, so I also re-flowed the joints on the resistors and the wires leading to the PCB.
 

·
Registered
Joined
·
341 Posts
Exploring thermal expansion further, surface mount cracks due to CTE differences often show up after many repeated thermal cycles: sometimes after as little as 500 or fewer cycles, but often after 3,000 or more cycles. The fact that something like this can show up after a great deal of cycling seems counterintuitive: it's more intuitive to surmise that cracks form from a sudden, high-impact force. Nonetheless, crack formation due to cycling differential expansion is well documented in the surface mount engineering literature.
I wonder if the number of extreme thermal cycles is actually quite low in some cases here. Obviously CTE is worse for a bigger change in temperature, so I wonder how often this board gets really hot, e.g. due to the car being parked facing the sun, so that solar heating of the cabin heats the board. Equally, very cold temperatures will be fairly rare, and may not always cycle from extreme cold to heated cabin very fast. Very cold morning starts to full defog and/or solar heated cabin to full AC might be the relevant temperature cycles though.

It may be that there also needs to be a coincidence between temperature extremes and shock/vibration as well, which would make the problem even harder to predict.
 

·
Registered
Joined
·
5 Posts
Just finished this fix on my 2009 Legacy. I didn't disconnect the battery, just unplug the connectors to remove power from the overhead unit. Easy fix. You can see the crack in the attached picture.
 

Attachments

·
Registered
Joined
·
257 Posts
Curious if this might be my problem BUT I do not experience any dimming or malfunctioning of the overhead passenger light; it seems to work as it should in any case, when there is someone is sitting in the seat or not (and if they are wearing their seatbelt). My car is a 2008 with 108K on it.

EDIT: I went ahead and tried the fix. I'm not sure how good my fix was but I used a computer repair kit and I had a de-soldering tool on hand. The overhead indicator WAS NOT functioning as it should (contrary to what I stated above), the "off" light was coming on and off; but I totally forgot there was an ON light, that is now working. WOW! I hope this fix lasts, I feel like my sloppy soldering may have torched some of the hardware (I kind of blackened some parts), we'll see. Thanks so much for this Thread!

Symptom: Dash cluster light, next to the brake warning light, was intermittent for 9 months or so, now it is always on. I had it in the shop for the timing belt and they ran the codes. I do see a code 26 "passenger airbag sensor" malfunction. Also, one of the brackets supporting the seat bottom, the one nearest to the gas pedal of the four, has broken away from the seat bottom, [still] not sure if this may be the cause.

Thanks in advance!
 

·
Registered
Joined
·
3 Posts
Thanks OP for this post. 20 minutes and a soldering iron is so nothing compared to what I expected when the light came on. Easiest fix ever.




* 3 days later - aaand the light is back ;_;
 
81 - 100 of 131 Posts
About this Discussion
130 Replies
85 Participants
sumie
Subaru Outback Forums
Welcome to the Subaru Outback Owners Forum, we have tons of information about your Subaru Outback, from a Subaru Outback Wiki to customer reviews.
Full Forum Listing
Top