My brake light are always on with the engine running??

GH85Carrera · GH85Carrera's Garage

Yea, I did a search, and all the brake light threads I found were for non working brake lights or just one side working.

Today I was checking my oil level at the dip stick, and I noticed the brake lights are just on. I had my wife stand behind the car, and hit the brakes and no change.

I do have Spoke's LED boards as my brake lights. The brake lights have been working just fine for years. No changes, no electrical work done in many months.

I know there are two pressure switches on the master cylinder, but those usually fail and the brake lights don't come on under light braking. This is not that issue.

So, any ideas as to why the lights are on all the time when the engine is running. And yea, as soon as the engine is turned off, they go out.

I will send a PM to Spoke and see if he has any ideas on a cure.

917_Langheck · 917_Langheck's Garage

This is the condition I had when I installed LEDs in the brake sockets - no change to bright as they were already bright. Some say it's a resistance issue, some say it's an issue with the two sensors at the M/C.

I'd check to see if all the individual LEDs are working; maybe one went out, and now the resistance has changed.

kmcteer · 07-29-2025, 11:19 AM

I had a similar problem and isolated it to the brake switches on the M/C. I'm only running LED bulbs, but may be worth a check.

-Kelly

GH85Carrera · GH85Carrera's Garage

I checked one other thing, the brake lights are on with just ignition on.

I guess it is time to replace the two master cylinder switches. Such a fun job!

PeteKz · PeteKz's Garage

When you previously wrote that the brake light was on when the engine was running kinda puzzled me. Thanks for the clarification.

mike sampsel · mike sampsel's Garage

You might try unplugging the forward switch and see if this stops the lights. Then maybe just replace the front switch for now. Or go for both, the rear one is not a lot of fun on mine.

MrBonus · 07-30-2025, 04:21 AM

The brake light switch is pretty easy to pull and check. A flat head and, I believe, a 5mm wrench is all you need as it can wiggle itself out of adjustment.

GH85Carrera · GH85Carrera's Garage

Quote:

Originally Posted by MrBonus

The brake light switch is pretty easy to pull and check. A flat head and, I believe, a 5mm wrench is all you need as it can wiggle itself out of adjustment.

On a Carrera like mine the switch on the pedal is only for the cruise control. The brake lights come on only with the two pressure switches on the master cylinder.

wazzz · wazzz's Garage

The two pressure switches on the 3.2 Carrera MC are simple switches wired in parallel. If only one of them gets stuck closed, your brake lights remain on. Maybe only one of your two switches is shot.

GH85Carrera · GH85Carrera's Garage

I will replace both of them "while I am in there" as they are both the same age. I will have to look up when I replaced them last time. It has been many years, and many miles. Last time the brake lights only came on if I was hard on the brakes.

GH85Carrera · GH85Carrera's Garage

Having a blast replacing my brake light pressure switches on the master cylinder. It was indeed the rear switch of course.

The front switch is not too bad to get to, the rear switch is a royal pain in the butt.

To make things more fun, the old switches need a 22 mm wrench, and the new ones need a 24 mm wrench.

The front switch is easy with a 22 mm deep socket. Just remove all the stuff in the way, and the deep socket makes it simple to remove and replace.

The rear one has the air controller box in the way to prevent using a socket. My only choice was a open end wrench. Again, 22 to remove the old switch, and a 24 to get the new one back on. And it was turn a little bit, turn the wrench over, and turn a little more and turn it over and do it again. The brake line prevents using the box end on the wrench.

My brake lights are no longer stuck on.

And just do a further search to the complete steps to R&R those switches. This update is just for future searches of a stuck on brake lights. If your brakes are stuck on all the time with a 3.2 Carrera, order two switches, and have fun.

917_Langheck · 917_Langheck's Garage

Quote:

Originally Posted by GH85Carrera

And just do a further search to the complete steps to R&R those switches. This update is just for future searches of a stuck on brake lights. If your brakes are stuck on all the time with a 3.2 Carrera, order two switches, and have fun.

To confirm, yours are 2 pole switches?

GH85Carrera · GH85Carrera's Garage

Yes. 2 pole. 1985 Carrera.