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Dash lights come on with brake lights and blinkers??


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22 replies to this topic

#1 bulwnkl

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Posted 19 February 2008 - 02:53 PM

My Baja ('05 turbo A/T) has a problem I first noticed yesterday. When I push on the brakes, the dash lights come on and the radio back-light dims. This also happens with the right turn signal, but not left. Right blinkers make the dash lights go on-off-on-off right along with the blinker.

I found an old thread here on USMB where someone had the same problem in an Impreza. Unfortunately, the OP never posted back and his subject line does not indicate the nature of the problem.

I followed the initial advice given in that thread and took the rear turn signal assembly out and checked the brake/turn signal bulb and connections. Everything looks completely clean and otherwise fine. I've also discovered that the front corners/markers/turn signals light up faintly at the RF. LF appears to do so extremely faintly as well (very tough to see in the bright sun today).

What in the world is going on and what do I do next? This issue is also posted here on Scoobytruck.com if anyone wants to look or post there.

#2 nipper

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Posted 19 February 2008 - 02:56 PM

Check all your lightbulbs. You may have to remove the break and turn signals bulbs one at a time till the problem goes away. You have a bad bulb, the filament is shorting out in the bulb causing a back feed.


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#3 bulwnkl

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Posted 19 February 2008 - 03:00 PM

Not necessarily at the right rear, I suppose? I'll keep taking things out until I find it. Can't find any dead shorts (all lights will light up appropriately), so I'm thinking you mean a fault that doesn't necessarily look like a used Polaroid flash bulb? For the sake of discussion, is there the possibility of Very Bad Things happening if I run like this for a couple/few days? Thanks for the help, Nipper.

P.S. Anyone ever tried LEDs in the stock tail-lights?

#4 nipper

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Posted 19 February 2008 - 03:03 PM

Its in one of the dual filament bulbs. The bulb may even look normal when you opertae it, thats why the bulbs have to be removed till the problem goes away. If you look at the bulb under a bright light you may even see the filament leaning against the other one.

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#5 Cougar

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Posted 20 February 2008 - 11:44 PM

I agree with Nipper. The right rear brake/tail light is the problem. Since the filaments are tied together this backfeeds voltage to the dash lights and is why you see what you do with the dash lights.

#6 Skip

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Posted 21 February 2008 - 10:44 AM

I agree with Cougar and Nipper

Here is another remote possiblity.

Someone "hamfisted", changed the bulb to a single pin.
This single pin shorts out the brake and parking light
contacts in the lamp holder.

I have seen this in Blokemobiles.(AH, Triumphs, MG's)

#7 Cougar

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Posted 21 February 2008 - 11:55 AM

That's a good one Skip. You're right! It could happen.

#8 Skip

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Posted 21 February 2008 - 11:59 AM

Thanks Cougar,
the hamfisted part comes from
the side pin config being wrong.

There may be a single filament lamp
with the offset side pins??
Why it would be this way is a question.

The double filaments has offset side pins
so the higher wattage filament gets connected to the
brake light.

#9 Bigbusa

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Posted 21 February 2008 - 12:32 PM

i agree with cougar nipper and skip

:grin:

#10 Gloyale

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Posted 21 February 2008 - 01:10 PM

I agree with Cougar and Nipper

Here is another remote possiblity.

Someone "hamfisted", changed the bulb to a single pin.
This single pin shorts out the brake and parking light
contacts in the lamp holder.

I have seen this in Blokemobiles.(AH, Triumphs, MG's)


+1

Someone has installed a ingle pole bulb, or the bulb has crossed filaments

#11 Gloyale

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Posted 21 February 2008 - 01:16 PM

........This also happens with the right turn signal, but not left. Right blinkers make the dash lights go on-off-on-off right along with the blinker.


This is the only confusing part. Don't Bajas have a seperate amber Turn signal? a crossed filament or improper bulb in the brakes should not affect the Turnsignal??

Is you're Baja wired for a trailer? Possibly a diode in the convereter box for the trailer has failed???

#12 aircraft engineer

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Posted 21 February 2008 - 03:22 PM

what he meant - is the baja wired for a single 2 filament bulb system trailer with a flasher converter? (Brake/turn on the same circuit) That's likely the cause if the circuit is like that (and that's 1 smart cookie out there :grin: )

The 3 bulb system trailer wiring is 3 separate circuits and doesn't use any additional circuitry except the "wires" and plug.

With the radio lights dimming on the flasher, you have a low amperage backfeed somewhere

#13 bulwnkl

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Posted 21 February 2008 - 10:35 PM

Sorry for not being able to follow up until now.

The problem is not in the RR lights. No changes, un-plugging, etc. impacted the problem. It appears that none of the lights are the problem.

Gloyale, the Baja uses a dual-filament bulb for brakes, markers, and blinkers. No separate amber turn signal (uses brake light bulb). The thing I haven't been able to check but I believe is the problem is the U-Haul trailer lighting converter box. Since they installed their box, I'm going to let them do the troubleshooting on it. I think there's a year warranty (it's not their hitch, just their wiring) on it, so I'm hoping there'll be a favorable outcome.

Thanks for the troubleshooting hints, tips, suggestions. I'll report again when I've been to U-Haul and back.

One question remains unanswered: Will running like this a while cause Very Bad Things? I've been running with the markers (aka parking lights) for the past couple days to mask/eliminate the problem.

#14 Cougar

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Posted 21 February 2008 - 11:39 PM

It shouldn't damage anything as far as I know. If things were causing excessive current flow a fuse would blow.

#15 nipper

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Posted 22 February 2008 - 10:42 AM

U haul?

Another thing to loo at is the terminal them selves.

What happens when you turn on the 4 ways?

There are not many places where these circuits cross to have a short.

nipper

#16 Skip

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Posted 22 February 2008 - 11:43 AM

U haul?

+1000
By chance do you have one of those "magic boxes"
to convert the trailer lights to work with the Baja lights???

I reread the entire post and saw no mention of this?

That could be the problem.

#17 Hondasucks

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Posted 22 February 2008 - 10:10 PM

U haul?


Uhaul, the Jiffy Lube of trailer hitches. I watched one of their droids spend 25 minutes fixing the wiring on a trailer I rented.... to repair like, one wire lol, for the license plate bulb...

#18 Gloyale

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Posted 22 February 2008 - 10:53 PM

Gloyale, the Baja uses a dual-filament bulb for brakes, markers, and blinkers. No separate amber turn signal (uses brake light bulb).


so...., there must be a diode in the circuit to seperate the turn/brake voltages. I have no idea where that diode would be mounted. But if you can locate it, it's easy to test and replace.

Usually in subarus, the diode is a cap that plugs onto a 2 prong connector. Looks like a capped off connector, but the cap is actually the diode. Ussually taped to the side of the harness somewhere.

#19 nkx

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Posted 24 February 2008 - 02:34 AM

P.S. Anyone ever tried LEDs in the stock tail-lights?


stay away from those LED bulb things. they dont provide enough directional light to work effectively. they basically only light up the area directly in front of it, instead of lighting up the entire housing. bad if you want people to actually notice if your brake lights/turn signals are on.

#20 bulwnkl

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Posted 24 February 2008 - 03:43 PM

Didn't get it to U-Haul yesterday so no info yet. Yes, there is a 'magic' convertor box for compatibility between the factory wiring and the trailer. Initially, I installed a box myself when I was installing the hitch. That box was DOA and the supplier wouldn't do ANYTHING except tell me I should search for contact info for the manufacturer and send it to them to replace. Timing was such that that didn't work for me, so I took it down to U-Haul to put a new one in. Sadly, they removed the factory harness plug when they put theirs in, but they used the same wiring points I had so they did wire it correctly (it has all worked fine for months).


I have thought about the U-Haul connector itself (where the trailer plugs in). It's very corroded now from the massive winter salt use here and because my 4-wire plug-in caps won't fit their double-stack connector thing.

Gloyale, thanks for the tip on the diode and where/what to look for to chase a diode. I'm hoping something to do with the trailer wiring is the issue because looking for that diode doesn't sound fun (I understand automotive electrical fine, but I HATE troubleshooting it!).

#21 Cougar

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Posted 24 February 2008 - 05:35 PM

I suggest you clean the corrosion from the connectors first. Doing that may clear the trouble. If it doesn't then if there is a way to disconnect the trailer convertor I would try that to see what happens.

To check for bad diodes it is best to use a digital meter, using the diode check function. Placing the probes across a good diode will show a reading of about .6 in the forward direction and a high reading in the reverse direction. If this problem is due to a bad diode you will most likely find one that is shorted.

#22 bulwnkl

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Posted 15 March 2008 - 08:24 PM

U-haul just replaced the convertor box and all corroded wiring/receptacles today. Problem solved, but I don't know for sure whether the issue was the box or the corrosion on the outlet. Thanks for the assistance, fellas.

#23 Cougar

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Posted 16 March 2008 - 09:45 AM

Thanks for the feedback Bulwnkl. Glad you got it fixed and you are welcome for the help.




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