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Brake warning light and MOT
Posted: Wed Jun 09, 2021 4:04 pm
by onthames
So I have the brake pad warning light on and have bridged the sensors and it stays on. Checked the solder joints on resistor. Can't get it to go off. Removed the bulb as have MOT tomorrow. When you turn the ignition on but don't start the car all the lights go on except the one I've removed. Then when you start the ignition they all go off. MOT fail or okay?
Re: Brake warning light and MOT
Posted: Wed Jun 09, 2021 4:15 pm
by paultv
As I understand, new MOT rules apply, if brake wear warning lamp is fitted, it should work correctly or you get a fail. same as the ABS light.
In fact the brake wear indicator only lights when the car is cranked - it earths through the solenoid on the starter - simply turning on the ignition will not
show a light - most MOT testers will have no idea about this behaviour - unless they are old school dudes.
Oh yes, if the lamp is always on when the bulb is fitted, you need to check the wear connectors close to the wheels, two at the front and I think one at the back -
if one of them is failing to connect due to crud it will cause the lamp to light - clean them out with switch cleaner, also check if voltage appears on the pins with a meter.
Paul
Re: Brake warning light and MOT
Posted: Wed Jun 09, 2021 4:36 pm
by onthames
paultv wrote: ↑Wed Jun 09, 2021 4:15 pm
As I understand, new MOT rules apply, if brake wear warning lamp is fitted, it should work correctly or you get a fail. same as the ABS light.
In fact the brake wear indicator only lights when the car is cranked - it earths through the solenoid on the starter - simply turning on the ignition will not
show a light - most MOT testers will have no idea about this behaviour - unless they are old school dudes.
Oh yes, if the lamp is always on when the bulb is fitted, you need to check the wear connectors close to the wheels, two at the front and I think one at the back -
if one of them is failing to connect due to crud it will cause the lamp to light - clean them out with switch cleaner, also check if voltage appears on the pins with a meter.
Paul
I bridged the connections on the sensors and checked with a multimeter (no voltage). When I turn the key, all the lights come on. Except the brake warning one because the bulb is removed. What I'm asking is do you guys reckon anyone will notice that?
Re: Brake warning light and MOT
Posted: Wed Jun 09, 2021 4:40 pm
by onthames
onthames wrote: ↑Wed Jun 09, 2021 4:36 pm
paultv wrote: ↑Wed Jun 09, 2021 4:15 pm
As I understand, new MOT rules apply, if brake wear warning lamp is fitted, it should work correctly or you get a fail. same as the ABS light.
In fact the brake wear indicator only lights when the car is cranked - it earths through the solenoid on the starter - simply turning on the ignition will not
show a light - most MOT testers will have no idea about this behaviour - unless they are old school dudes.
Oh yes, if the lamp is always on when the bulb is fitted, you need to check the wear connectors close to the wheels, two at the front and I think one at the back -
if one of them is failing to connect due to crud it will cause the lamp to light - clean them out with switch cleaner, also check if voltage appears on the pins with a meter.
Paul
I bridged the connections on the sensors and checked with a multimeter (no voltage). When I turn the key, all the lights come on. Except the brake warning one because the bulb is removed. What I'm asking is do you guys reckon anyone will notice that?
Hold on... Can anyone confirm this: "two at the front and I think one at the back"
I thought only one at front and back. This may be the issue.
Re: Brake warning light and MOT
Posted: Wed Jun 09, 2021 5:33 pm
by paultv
Just checked, you are right FL RR so two!
and maybe no one will notice..
also power is only evident in RUN or START - so when the engine is running or during cranking.... also check fuse 10 is good
Paul
Re: Brake warning light and MOT
Posted: Wed Jun 09, 2021 5:57 pm
by onthames
Fuse 10 all good. I'm talking about when I put the key in the second position, two clicks, before turning to start.
Re: Brake warning light and MOT
Posted: Wed Jun 09, 2021 7:32 pm
by paultv
The lamp should only light during cranking the engine, and go off when the engine is running assuming the two sensors are connected ...the sensors are in series, so any bad connection will produce a permanent light on.
Re: Brake warning light and MOT
Posted: Wed Jun 09, 2021 9:46 pm
by Brianmoooore
AFAIK, a brake pad/lining wear light is not testable in a UK MOT test.
The warning loop runs between pin 26 of the white instrument cluster plug (blue/green wire) and pin 21 of the blue plug (blue/white wire). The loop is essentially a continuous wire, so there should be very little resistance between these two pins of the plugs.
The pad warning light should come on if the loop becomes open circuit, or if it is shorted to earth.
Re: Brake warning light and MOT
Posted: Thu Jun 10, 2021 10:49 am
by paultv
I've searched and it was added in April...BUT may not apply to our age range of car...any testers on here to confirm or deny??
Paul
Re: Brake warning light and MOT
Posted: Thu Jun 10, 2021 2:18 pm
by onthames
I managed to get it off briefly but when I took the instrument panel out again and put back it turned back on. Deffo a connection somewhere. Couldn't locate it so far but have unplugged bulb as need MOT done today. Going somewhere else and hope it passes.
Re: Brake warning light and MOT
Posted: Thu Jun 10, 2021 2:29 pm
by Brianmoooore
Just back from an MOT test today. Meant to ask, but unfortunately forgot!
It does sound like the resistor problem. Sure you soldered the right joints?
Re: Brake warning light and MOT
Posted: Thu Jun 10, 2021 2:47 pm
by onthames
Brianmoooore wrote: ↑Thu Jun 10, 2021 2:29 pm
Just back from an MOT test today. Meant to ask, but unfortunately forgot!
It does sound like the resistor problem. Sure you soldered the right joints?
Yep, it seems more like the wiggling the blue connector makes the difference to be honest. I cleaned all the pins and made sure the wires weren't tugged out by someone who didn't know how to undo the clip, all seemed fine.
Re: Brake warning light and MOT
Posted: Thu Jun 10, 2021 4:18 pm
by onthames
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A miracle
Re: Brake warning light and MOT
Posted: Thu Jun 10, 2021 7:09 pm
by Brianmoooore
Snap! I've got one just like that.
Have you checked the soldered joints of the blue and white sockets are soldered to the main circuit board? They're not a weak point, but if someone pulls on the plugs hard enough...........
Re: Brake warning light and MOT
Posted: Thu Jun 10, 2021 8:22 pm
by onthames
Brianmoooore wrote: ↑Thu Jun 10, 2021 7:09 pm
Snap! I've got one just like that.
Have you checked the soldered joints of the blue and white sockets are soldered to the main circuit board? They're not a weak point, but if someone pulls on the plugs hard enough...........
No surprises there ;)
Going to give it a break for now but I'll check next week. I tell you, this morning I thought I had it all fixed and put the whole thing back together. Put it in the car, put all the screws in, turned it on, light came on again. Taking the instrument panel out now is like an F1 pit stop for me. I must have had it out 10 times in the past 2 days, naively putting all the screws back in each time because I think I've fixed it!
I went to a new place for the MOT and the tester was into his BMWs. He did spot a few very small oil leaks and pointed out one of the brake hose ends was corroded.
We also spoke about how the some of the bushings had dried out but he said there was no play so that was all fine. Very happy with the result.
Re: Brake warning light and MOT
Posted: Thu Jun 10, 2021 9:37 pm
by Brianmoooore
My tester actually drives an E30 as his personal (as opposed to family) transport, so we spent a good deal of the test time talking about that. It's only a 1.6i, and he wants to keep it as that, but he wants to rebuild the engine as a world beating 1.6i.
I got away with a minor bit of play on a front ARB link, and minor wear in the RH front control arm ball joint. Neither enough to warrant a fail, but they'll be changed anyway.
Re: Brake warning light and MOT
Posted: Thu Jun 10, 2021 10:51 pm
by onthames
Brianmoooore wrote: ↑Thu Jun 10, 2021 9:37 pm
My tester actually drives an E30 as his personal (as opposed to family) transport, so we spent a good deal of the test time talking about that. It's only a 1.6i, and he wants to keep it as that, but he wants to rebuild the engine as a world beating 1.6i.
I got away with a minor bit of play on a front ARB link, and minor wear in the RH front control arm ball joint. Neither enough to warrant a fail, but they'll be changed anyway.
Did you scout out an E30 owner for your MOT
?
thanks for the help Brian. I was looking through your old posts on the brake pad subject and noticed your first ever post on this new forum was on the subject. 16 years later you still put in the time to answer the same old questions. Appreciated!
Re: Brake warning light and MOT
Posted: Tue Jul 06, 2021 8:26 pm
by Binkerment
Was this issue ever resolved?
I currently have the same issue with mines. Not carryed out any extensive testing yet apart from bridging the pins on the front left sensor plug. I've noticed if a brake heavy the light will flicker but never fully go off. As soon as a release the brake the light stays on
Re: Brake warning light and MOT
Posted: Tue Jul 06, 2021 10:58 pm
by onthames
Binkerment wrote: ↑Tue Jul 06, 2021 8:26 pm
Was this issue ever resolved?
I currently have the same issue with mines. Not carryed out any extensive testing yet apart from bridging the pins on the front left sensor plug. I've noticed if a brake heavy the light will flicker but never fully go off. As soon as a release the brake the light stays on
pads okay? sounds like the sensors working might just need replacing. Mine wasn't a sensor issue so I just removed the bulb. but urs sounds like a sensor issue to be honest
make sure if you do replace you buy different ones for front and back cos they are different i think
Re: Brake warning light and MOT
Posted: Wed Jul 07, 2021 8:17 pm
by Binkerment
I've bridged out the front sensor but still to do the rear. Is the plug easy to get to woth the wheel off or will I need to be u der the car?
Re: Brake warning light and MOT
Posted: Wed Jul 07, 2021 9:57 pm
by onthames
Binkerment wrote: ↑Wed Jul 07, 2021 8:17 pm
I've bridged out the front sensor but still to do the rear. Is the plug easy to get to woth the wheel off or will I need to be u der the car?
wheel off is fine