Help! Brake lights stuck on!

Odd Job · 27th September 2019, 11:29

Quote:

Originally Posted by SD1too

Richard; the reason for the suggestion that you check fuse 13 (in the passenger compartment fusebox) is that it is a 12v supply to the Light Switch Module (LSM), as is fuse 25. The LSM controls all exterior lighting including the brake lights. It is therefore possible that, if either of these 12v supplies is missing, the LSM could enter a fail-safe mode and illuminate the brake lights continuously.

However, you have reported that on arrival at work the brake lights had reverted to normal operation. This might indicate an intermittent fault.

Please check these two fuses, numbers 13 and 25, and I also have two questions for you:

Are all 3 brake lights illuminated or just some of them?
Is the brightness of the brake lamps normal or at the lower level associated with a tail lamp?

You need not worry about the CAN bus because it isn't involved in brake light operation.

Simon

I cant find any fuses blown.

When the lights were on, all 3 stop lamps were the "normal" brightness as if the switch was activated.
I checked all the other lights and everything else was working fine.

I've checked twice a day since it happened and so far, all good.

Richard

SD1too · 27th September 2019, 12:37

Thanks for your reply Richard. Until the fault recurs there's not a lot you can do. I think you're going to need the services of a multimeter though, starting with the brake pedal switch.

Simon

squire · 27th September 2019, 12:48

I had similar problems two or three years ago. Brake lights would go ok for a week or so then stick on, reset brake light switch then ok for a while but eventually got worse.

A new brake light switch from Rimmers cured the problem in the end, but not a nice job to do. Also, only get the switch from Rimmers, eBay ones do not work

.

27th September 2019, 12:37	#2
SD1too Doesn't do things by halves Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007 Location: Former Middlesex Posts: 20,469 Thanks: 1,587 Thanked 3,749 Times in 3,181 Posts	Thanks for your reply Richard. Until the fault recurs there's not a lot you can do. I think you're going to need the services of a multimeter though, starting with the brake pedal switch. Simon __________________ "Whatever is rightly done, however humble, is noble." Sir Henry Royce.

27th September 2019, 12:48	#3
squire Posted a thing or two MGB GT, 2 Morris Minor Travellers Join Date: May 2011 Location: Bilston Posts: 1,667 Thanks: 1,610 Thanked 497 Times in 370 Posts	I had similar problems two or three years ago. Brake lights would go ok for a week or so then stick on, reset brake light switch then ok for a while but eventually got worse. A new brake light switch from Rimmers cured the problem in the end, but not a nice job to do. Also, only get the switch from Rimmers, eBay ones do not work.