Red Brake Light in Dash - PeachParts Mercedes-Benz Forum

photomatt · #1 08-27-2007, 10:32 PM

Hi all. On my 1985 300D, the Red Brake light is always lit on the dash. To my knowledge, this is for the "parking brake on" indicator, right? Does this indicate problems anywhere else in the braking system? I've looked high and low for the switch that turns it on when you apply the parking brake and can't find anything that seems to be it. Can anyone shed some light on this? Is it OK to drive it like this? There seems to be no problem with the brakes and how they are working, pads are good and calipers have been replaced. Can the switch, once it is found, be adjusted or replaced? Thank you for all your help on this. Matt

#2 08-27-2007, 10:35 PM

That light will also indicate low brake fluid level. Make sure both the front and rear parts of the master cylinder are full.

photomatt · #3 08-27-2007, 10:41 PM

I've filled the Master cylinder to the "max" line. That should fill both front and back, correct? Thanks

#4 08-27-2007, 10:47 PM

It should, but there is a divider in the tank, make sure the back half is really full. Also, make sure the electrical connector on the master cylinder is OK, if it's loose you may get a light.

photomatt · #5 08-27-2007, 10:48 PM

I'll check these out. Thanks, Matt

Motorhead · #6 08-27-2007, 10:49 PM

Do your brakes feel "not so good?" I think the light will tell you if one of the two brake hydraulic circuits is not functioning.

pawoSD · #7 08-27-2007, 10:49 PM

Quote:

Originally Posted by photomatt

I've filled the Master cylinder to the "max" line. That should fill both front and back, correct? Thanks

Yes.

Most likely the light is on because your parking brake pedal is not coming back up all the way, lift it up with your foot and the light will likely go out. This happens when there is some slack on the parking brake cable or the mechanism is worn out and sloppy. Thus the pedal doesn't bounce all the way back up and press the switch to make the light go out. Also, the switch itself is located right up above the middle of the parking brake pedal assembly....its the same kind of switch used on the for the interior light in the door jams...etc. The lights stay on in both of our SD's too....our 300D has a perfect parking brake system, and it actually goes out when releasing the brake.

pawoSD · #8 08-27-2007, 10:51 PM

Quote:

Originally Posted by Motorhead

Do your brakes feel "not so good?" I think the light will tell you if one of the two brake hydraulic circuits is not functioning.

The light only tells you if the parking brake pedal is down (or not up all the way) or if the fluid in the brake resevoir is very low....thats all it does...its just a simple circuit with a few switches and a light bulb.

photomatt · #9 08-27-2007, 10:57 PM

The brakes "feel" just fine. The brake fluid is just a bit above MAX right now. I've tried lifting up on the parking brake pedal but that doesn't seem to help. Is the switch hidden up above the brake pedal? I just can't seem to find it. Can it be adjusted? Should I just live with the light on? It seems like it would be such an easy problem to fix. Hmmmmmm........

Thanks again, Matt

pawoSD · #10 08-27-2007, 11:01 PM

I've never really tried to deal with it, as my parking brakes died about a year ago with a weird snapping sound....and now the pedal stays "in the middle" of the travel it can go....and the brakes are not applied at all. The pedal springs back either way you push it...so...my light stays on. I am just waiting and waiting for the bulb to go out.

On our '83 it stays on just because of slop in the brake system....which also doesn't work....it works enough to make it hard to push on level ground....

The switch is mounted to the pedal/wratchet assembly right up above the pedal arm. Maybe your switch is broken or stuck and thats why it won't go out when pulling up on it. It is right on there though....its black...so it blends in....

tangofox007 · #11 08-27-2007, 11:02 PM

You might try disconnecting the two elecrical connectors on the master cylinder reservoir. If the light remains on (I'll bet it won't) then you know that the parking brake is the culprit.

photomatt · #12 08-28-2007, 06:05 AM

Thank you to all! I'll try these things today! It is a really good feeling that I am not alone with this issue. Thanks again, Matt

lonewolftek · #13 08-28-2007, 11:02 AM

You are most certainly not alone! I've been trying to fix the brakes on my '84, and the further I dig in, the more it seems I'm going to be replacing.

Seems the PO let the brake fluid level get really low - there wasn't any fluid in the reservoir when I got it, and stopping the car was a scary experience. I've also got some wicked pulsation and noise coming from the pass. side when the brakes are applied.

Of course, the quick fix is to pull the instrument cluster and disconnect that light