Author Topic: Mazda 3 rear lights go off when brakes are pressed  (Read 1772 times)

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Offline mazdal3

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Mazda 3 rear lights go off when brakes are pressed
« on: January 30, 2018, 05:48:43 PM »
Hi, can anyone help restore my sanity?

Car is Mazda 3 2.0 sport 2005

This is the issue:

My rear lights have been playing up. They are LEDs. They come on (although sometimes not both side) but if I touch the brakes they go off and stay off. They will only come back on again if i switch them off and back on. Also only left brake light comes on and middle window light, yet both rear lights work.

What I've done: (i am no mechanic and don't know much about multimeters etc but here goes)

I replaced the brake switch. No change.
I disconected the brake switch and put a jumper wire on it - no change.
I stripped a bit of black off a wire going in to the light (did both sides)  and then put a screw into the body. Joined them - no change.
I Put the multimeter probes on the red wire and the other (orange I think) not the black - it read 14v - did this both sides. I assume this means power is reaching the lights.
I put a multimeter probe on the black wire in the plug and the other to the body to check for continuity - i got a beep - did it both sides so I assume the earth reaches the lights. Or at least the plug side of the lights.
I wired the lights directly to some power and both sides lit up.

Other than go to a auto electrician, I'm struggling to know what to do next. I'm thinking maybe an issue with the indicator stem??

ANyone got any ideas - i'm skint and have just replaced my dishwasher so a pro repair is going to hurt this month.

Offline Willpower

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Re: Mazda 3 rear lights go off when brakes are pressed
« Reply #1 on: January 30, 2018, 06:05:25 PM »
Just generally reading through your problem the first thing that springs to mind is Earthing. You haven't mentioned checking this.  All sorts of electrical problems occur due to a poor earth.  As an immediate action I would check all the earth contact points (found in the engine compartment) for cleanliness and security.  See if that solves your problems 
Look at life through the windscreen, not the rearview mirror.
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Offline mazdal3

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Re: Mazda 3 rear lights go off when brakes are pressed
« Reply #2 on: January 30, 2018, 06:13:01 PM »
Just generally reading through your problem the first thing that springs to mind is Earthing. You haven't mentioned checking this.  All sorts of electrical problems occur due to a poor earth.  As an immediate action I would check all the earth contact points (found in the engine compartment) for cleanliness and security.  See if that solves your problems

I did check where the negative terminal on the battery connects to the body and that was fine. Not sure where else I can look ? Are there other connections under the bonnet. The only earth I checked was the black wire at the plug end where it goes in to the light socket. the multimeter beleeped when i checked for continuity with that and the body.

 My wife just asked me to go to the shop and I had to walk. I can't use the car at night. so at least something positive here, it's helping my fitness. :)

Offline moozmooz

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Re: Mazda 3 rear lights go off when brakes are pressed
« Reply #3 on: January 30, 2018, 08:23:34 PM »
Are these standard light clusters or aftermarket? "if I touch the brakes they go off and stay off" suggests a fault in the LED assembly. If your LED lights are just LED bulbs, I'd suggest getting some standard bulbs and seeing if the problem persists. Cheaper than an hour at an auto electrician.

Offline mazdal3

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Re: Mazda 3 rear lights go off when brakes are pressed
« Reply #4 on: January 30, 2018, 08:39:46 PM »
Are these standard light clusters or aftermarket? "if I touch the brakes they go off and stay off" suggests a fault in the LED assembly. If your LED lights are just LED bulbs, I'd suggest getting some standard bulbs and seeing if the problem persists. Cheaper than an hour at an auto electrician.

Standard I think. I didn't add them anyway. They are clusters of LEDs. I rang a dealer to see how much for new ones and I think it was in the region of £170 quid. I'd be happy to change for standar bulbs if it meant sorting it.

**UPDATE** I moved the plugs that go into the sockets in the lights around abit - did some wiggling and things kept changing. SOmetimes everything worked perfect, sometimes not. sometimes the lights came on and sometimes not. I'm tempted to cut the plug and sockets off, strip back the wires and use connector block to see if that helps. Bad idea?

Cheers for the answers so far. Much appreciated.

Offline moozmooz

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Re: Mazda 3 rear lights go off when brakes are pressed
« Reply #5 on: January 30, 2018, 11:47:08 PM »
I've never had to change a bulb on the rear lights of my 2005 hatch, but looking at the manual here http://www.mazda3forums.co.uk/workshopmanual/  the brake/taillight bulb is listed as either a conventional 21/5W or a 4/0.4W LED.
I'd assume the offset bayonet is the same with both types and Mazda have opted to use LEDs in some and filament bulbs in others, so you should still be able to try a couple of 21/5W filament bulbs and see if it cures the problem. The only concern I would have is that the fuse rating may be lower if LEDs are fitted, but I can't find anything in the online manual to check against and my 2005 hatch manual's not here.

Offline mazdal3

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Re: Mazda 3 rear lights go off when brakes are pressed
« Reply #6 on: February 01, 2018, 04:54:59 PM »
Thanks for the reply. I haven't replied while I have been trying a few things.

I have cut the plug and socket off the light and the wiring to the light and joined them with connector blocks, but still no joy.

I put the tester on the solder points on the circuit board for the LED. The earth is fine. The lives get 14v to them even when the lights are off and brake not pressed. when the brake is pressed or the lights on, they get no power. I have no idea what this means, but it's starting to do my head in a bit. I did a bit of autotrader browsing last night and if i had the money...

Offline mazdal3

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Re: Mazda 3 rear lights go off when brakes are pressed
« Reply #7 on: February 06, 2018, 02:32:03 PM »
Finally paid for a pro to come out and take a look. He reckons that something has gone wrong with the LED circuit boards inside the lights. He recommended me getting new lights.

anyone know of a good place to shop for two rear light units?

Offline StevenRB45

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Re: Mazda 3 rear lights go off when brakes are pressed
« Reply #8 on: February 06, 2018, 06:18:38 PM »
Unless you've got a good local breaker I'd have a look on eBay, last time I was on there was loads.

Offline mazdal3

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Re: Mazda 3 rear lights go off when brakes are pressed
« Reply #9 on: February 06, 2018, 10:51:45 PM »
Unless you've got a good local breaker I'd have a look on eBay, last time I was on there was loads.

Cheers I have been. Tried 2 local breakers today but no joy.  Only snag I have when looking on ebay is that the lights i am taking out are the LED cluster version, they are really pricey on Ebay. I'm happy to replace with the standard bulb type. The auto electrician said they would work, but i'm not 100%sure that they will fit. DOes anyone know if they will fit?

Rang mazda and they didn't know, but they did quote me 205.74 for drivers side and 196 for other side both +VAT.  :o

Offline StevenRB45

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Re: Mazda 3 rear lights go off when brakes are pressed
« Reply #10 on: February 07, 2018, 09:07:59 AM »
They should be bolt out bolt in, but a quick eBay scoot has a pair of Mazda 3 sport lights at 200 and about 130 for bog standard ones. So you pays your money..

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Offline mazdal3

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SOLVED: Mazda 3 rear lights go off when brakes are pressed
« Reply #12 on: March 06, 2018, 08:47:56 PM »
For anyone else with this problem - I solved it by replacing both rear lights. There must have been a fault on the circuit boards. Mazda wanted 500 quid for two lights but on Ebay I found a guy breaking a Mazda 3 and bought both LED lights for 80 in total. Thanks for all of the advice.

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SOLVED: Mazda 3 rear lights go off when brakes are pressed
« Reply #12 on: March 06, 2018, 08:47:56 PM »