is the brake pad wear indicator an MOT failure? 20 July 2022 at 2:48PM in Motoring 11 replies 1.5K views

thegentleway

is the brake pad wear indicator an MOT failure?

facade

No, an illuminated brake pad wear indicator is not a reason for failure.

(1.1.13. Brake linings and pads)

However, brake pads worn down to the wear indicators are a major, and worn to less than 1.5mm are a dangerous, both are failures.

Presumably if the light is on due to a fault or a broken wire, it is a pass, if it is on due to wear, a fail.

Spies

Get them replaced or you'll end up needing discs too.

Bigwheels1111

Ok for mot, but sensor will be quite an added cost when replacing brake pads.
£20-£30 for wear indicator if your lucky.
To avoid this I ordered one of these, it also stops dodgy garages telling you need brakes when you don’t.

https://www.amazon.co.uk/gp/product/B01LYZZR2J/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I had 8mm left when they told me mine needed replacement. Only 1/3 worn.

Alanp

Am I missing something here…I’m sure that any light on the dash is an mot fail, or do you mean the wear at the pad that hasn’t yet caused the light on the dash to illuminate?

400ixl

Bigwheels1111 said:

Ok for mot, but sensor will be quite an added cost when replacing brake pads.
£20-£30 for wear indicator if your lucky.
To avoid this I ordered one of these, it also stops dodgy garages telling you need brakes when you don’t.

https://www.amazon.co.uk/gp/product/B01LYZZR2J/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I had 8mm left when they told me mine needed replacement. Only 1/3 worn.

Not sure what car you had, but typically you don't replace the sensor other than the part which is embedded in the new brake pad. Usually it is either audible or electronic, both working in a similar way with a piece of metal in the pad which either screeches when the pad wears and it touches the disk or completes a circuit which is what activates the warning light. The metal is in the pad and is replaced as part of it, none of the electrical part of the sensor is replaced usually.

facade

Alanp said:

Am I missing something here…I’m sure that any light on the dash is an mot fail, or do you mean the wear at the pad that hasn’t yet caused the light on the dash to illuminate?

No, only the airbag/SRS light, abs & ESC lamps and engine management lights are a fail (Strictly only if they are indicating a malfunction, but realistically if they are permanently on)

1.1.13. Brake linings and pads

Some brake pads have metal wear indicators so that when the pads become excessively worn the metal indicator touches the disc making a squealing sound. Other pads may have a cut, which if worn away indicates that the pad must be replaced.

An illuminated brake wear indicator is not a reason for failure.

Defect	Category
(a) Brake lining or pad: (i) worn down to wear indicator (ii) worn below 1.5mm	Major Dangerous
(b) Brake lining or pad contaminated with oil, grease etc.	Major
(c) Brake lining or pad missing or incorrectly mounted	Dangerous

https://www.gov.uk/guidance/mot-inspection-manual-for-private-passenger-and-light-commercial-vehicles

Bigwheels1111

400ixl said:

Bigwheels1111 said:

Ok for mot, but sensor will be quite an added cost when replacing brake pads.
£20-£30 for wear indicator if your lucky.
To avoid this I ordered one of these, it also stops dodgy garages telling you need brakes when you don’t.

https://www.amazon.co.uk/gp/product/B01LYZZR2J/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I had 8mm left when they told me mine needed replacement. Only 1/3 worn.

Not sure what car you had, but typically you don't replace the sensor other than the part which is embedded in the new brake pad. Usually it is either audible or electronic, both working in a similar way with a piece of metal in the pad which either screeches when the pad wears and it touches the disk or completes a circuit which is what activates the warning light. The metal is in the pad and is replaced as part of it, none of the electrical part of the sensor is replaced usually.

Reading the post I thought the car had one of the wear indicator sensors that attached to the pad.
Wear down with the pads and puts the light on,
Once they set the light off they need replacement.
Had them on my Vectra, £20 each side.

thegentleway

Thank you @facade - that's very helpful.

Bigwheels1111 said:

400ixl said:

Bigwheels1111 said:

Ok for mot, but sensor will be quite an added cost when replacing brake pads.
£20-£30 for wear indicator if your lucky.
To avoid this I ordered one of these, it also stops dodgy garages telling you need brakes when you don’t.

https://www.amazon.co.uk/gp/product/B01LYZZR2J/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I had 8mm left when they told me mine needed replacement. Only 1/3 worn.

Not sure what car you had, but typically you don't replace the sensor other than the part which is embedded in the new brake pad. Usually it is either audible or electronic, both working in a similar way with a piece of metal in the pad which either screeches when the pad wears and it touches the disk or completes a circuit which is what activates the warning light. The metal is in the pad and is replaced as part of it, none of the electrical part of the sensor is replaced usually.

Reading the post I thought the car had one of the wear indicator sensors that attached to the pad.
Wear down with the pads and puts the light on,
Once they set the light off they need replacement.
Had them on my Vectra, £20 each side.

Exactly, except I don't replace the sensors to save money. I shorted the wires togethers the first time I change the pads and discs so the light wouldn't be on. Presumably the wires have corroded and the light is back on just when the MOT is due and I don't have access to my tools!

facade

thegentleway said:

Thank you @facade - that's very helpful.

Exactly, except I don't replace the sensors to save money. I shorted the wires togethers the first time I change the pads and discs so the light wouldn't be on. Presumably the wires have corroded and the light is back on just when the MOT is due and I don't have access to my tools!

In The Olden Days there was a sensor wire "chain"  round the 4 wheels. The sensors were a piece of bare wire embedded in the pad that had 2 connections to join the chain together.  At the end of the chain was the handbrake switch (via a diode). with the handbrake on the pad wear lamp lights up as a test. If any of the pads wear, the sensor wire shorts to the disc and puts the pad wear light on. If a sensor wasn't connected. the light wouldn't come on with the handbrake. (so we used to cut the wires off the old pads and just connect them to maintain the chain to fit the half price pads)

No doubt nowadays the ecu senses if the circuit is open (sensor disconnected), or shorted to earth (pad worn), but I'd still be looking for a short to earth at the sensor wires first.

400ixl

Bigwheels1111 said:

400ixl said:

Bigwheels1111 said:

Ok for mot, but sensor will be quite an added cost when replacing brake pads.
£20-£30 for wear indicator if your lucky.
To avoid this I ordered one of these, it also stops dodgy garages telling you need brakes when you don’t.

https://www.amazon.co.uk/gp/product/B01LYZZR2J/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I had 8mm left when they told me mine needed replacement. Only 1/3 worn.

Not sure what car you had, but typically you don't replace the sensor other than the part which is embedded in the new brake pad. Usually it is either audible or electronic, both working in a similar way with a piece of metal in the pad which either screeches when the pad wears and it touches the disk or completes a circuit which is what activates the warning light. The metal is in the pad and is replaced as part of it, none of the electrical part of the sensor is replaced usually.

Reading the post I thought the car had one of the wear indicator sensors that attached to the pad.
Wear down with the pads and puts the light on,
Once they set the light off they need replacement.
Had them on my Vectra, £20 each side.

Quite rare for a lot of years for the wear indicator to not be built into the pad itself these days. So yes it could have been a case some years ago, far less likely now.

It would potentially have a wire which connects to the pad which is used to connect to the pad, but that doesn't need changing when the pad wears, just re-connecting to the new pad. Only time it would need replacing would be if it was physically damaged which would not be caused by the pads wearing.