Brake fuse keeps blowing STX550

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karlos_1984

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Hey guys.
For months now I've been having constant issues with the brake light fuse blowing. It seems worse whenever its a hot day. Basically, I've had no issues with this until I had an ARB canopy fitted last year. It has the brake light in the rear window and from what I can see it's just wired into the right side tail light.
I've replaced both rear brake globes, have tried cleaning the trailer plug and spraying it with WD spray in case there was any dirt etc in there. As soon as you replace the 10A fuse in the glove box, the brake lights work again for about 2-5 pedal presses before it blows again. This is doing my head in. Can anyone give any advice? Thanks.
 
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Does the light in the canopy work? If it has only started happening since having that fitted I'd either take it back and make them fix it or trace the wiring and make sure it is insulated properly. If the wiring is OK, I'd suspect the light being faulty, but wiring is easy and free to check if you want to do it yourself.
 
take out the brake light bulb from canopy and see if the fuse blows then. if it doesn,t blow a fuse you know the problem is between the canopy light and the right rear power connection.
 
or disconnect it at the tail light first.
I had the same issue on a different car once. it was the traier wiring harness rubbing thru on the chassis1
 
As above. Some simple checks can be made, the first thing I'd be doing is disconnecting the canopy wiring and seeing if 10 pedal presses are ok, then 20, then 30. Then reconnect and see what happens.

Brake bulbs are 21/5 watt (5W in 'parker' mode and 21W in 'brake' mode). Two of those is 42W or about 3.5 amps. An LED strip should consume about 2A, so you're looking at 5A for the whole lot of lights at the back. If unplugging the canopy works, it's not because the fuse is overloading so do NOT think "Oh I'll fix it by whacking in a 20A fuse!". There must be a problem in the canopy wiring.

As per Eric, there may well be something wrong with the trailer harness as well. Everything on a car moves, including cables, which chafe against whatever they're passing and can easily wear through the insulation so the inner conductor touches something else.

If unplugging the canopy does NOT fix it, either take it to an auto electrician or grab a multimeter and start testing for leaks to the chassis. Personally I'd remove the two tail light sections (both left and right) and dismantle them, cleaning all of the electrical contacts and then reassembling. I had (on my Navara) a dirt issue in the left hand brake light which caused all sorts of stupidity with the tail lights on the back. A quick clean and all was good again.
 
Update: I spent a couple hours in the shed yesterday doing some tests, trying to isolate the fault. The canopy was fitted over 12 months ago, and this fault has only started the past couple months, so I'm thinking something has worn through and a wire must be shorting out somewhere. I pulled the canopy interior light out and traced all the wiring for the brake light in the canopy. The wiring from the canopy brake light that runs down into the right hand side tail light is as rough as guts. Appears the muppets at ARB have cut it too short (twice) then soldered two smaller lengths onto the main length of wire so it would reach the tail light. Their soldering job and use of tape to insulate the joints is awful. I tidied all this up, refit everything and did a heap of brake tests in the shed and it all seemed to be working. Went out n ran a few errands around town for about half an hour, then bang, blown fuse again. Changed the fuse to have brake lights to get home, but it blew straight away. I've since come home and cut the positive wire that runs from the tail light up into the canopy's brake light to take it out of the equation. Have fitted a new fuse and the brake lights (less the canopy one) are working fine. I'm going to drive it like this for the next few days to see if the fault replicates again. If not then I'm going to re-wire the canopy's brake light properly and replace the dogs breakfast of a job that ARB have done. They're obviously done a rushed job when fitting it.
 
Good to see that you're on the way to finding the issue. Pretty average when you think about it, but I guess it is getting the same in a lot of bigger chain stores now. Nobody seems to take any pride in their work anymore...
 
a mate has a subaru outback and he has had the exact same issue with the tailgate brake light blowing. he checked the wiring harness that comes from the tailgat light and sure enough partially broken wire . this must be a common issue with this particular outback model as the way the harness is designed every time the tailgate is opened / closed the harness wires bend up and down each time, so after some time a wire breaks.
 
Good to see that you're on the way to finding the issue. Pretty average when you think about it, but I guess it is getting the same in a lot of bigger chain stores now. Nobody seems to take any pride in their work anymore...

I couldn't agree more. Its disgusting how no one gives a shit anymore. Everything is cost cutting, rip tear bust, and passing the buck with any form of responsibility when it comes to poorly done work. Even my work shirts (which are supplied by the company) are getting bad. Got 6 new shirts at the start of the month and I've already had the buttons fall off because they're made with about 0.5 mm of cotton to sew the buttons on. But yeah, I went with ARB due to their reputation, I expected better quality of work than this.
 
Update: So after disconnecting the canopy brake light completely as described in my previous post, (17/01/18) I've had no issues...Until Friday 2nd Feb.
I don't know what's happened, but I'd driven to/from work and around town for a good couple weeks with no issues. I went away last weekend and on the way home, blew brake fuse again. The canopy wiring is still disconnected and out of the equation. I changed fuses 4 times and as soon as you press the brake pedal, bang. It's getting beyond the joke now. I can't explain why it worked fine for 2 weeks then has just started blowing fuses again. I've pulled all the tail lights out and traced wiring down to the trailer plug, but cannot for the life of me find any wiring that has worn through and/or shorting out. Does anyone else have any suggestions? Old.Tony you mentioned getting a multimeter and checking for leaks to chassis, what's that involve?
 
If you have a multimeter, check both wires inside the brake light globe socket for continuity to earth on the chassis. You may also have to get under the tub and disconnect the main loom and check from that back to the tail lights. It is definitely a weird one.
 
I'd also check the trailer plug.

Multimeters are easy to use. There are two leads - the black one should be in "COM" or "-" (that's a minus). The red lead should be in "Normal", "+" or the one that is NOT labelled "10A".

Turn the dial to read "Ohms" - it's the omega symbol, the display should change to "infinite" or "unknown" or some symbol/numeric that represents "unmeasurable". There might be scales on the selector dial - 1-100ohms, 100-1000ohms etc. Doesn't matter which one you choose, a short (which is what you're looking for) reads zero. Touch the two leads together to confirm, the display should change to 0.

Now go to the back of the car, pop the tail light out and look at the socket for the brake bulb. It will have two pins in the bottom. Touch the black lead to part of the body and touch the red lead to the inner surround of the socket - this should result in a reading of 0 (because the surround should be negative). Now touch the two pins - there should be either a high (large number) reading or "infinite".

If it shows a short, it's most likely in the trailer plug. Best thing to do is unscrew it and pull it apart - it could be full of mud/dirt (mine was) and if any of the contaminant contains metallic particles there's your answer. Clean, reinstall, retest.
 

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