LED Stays On

[money pit]

I'm installing aftermarket gauges on my dash. I installed an LED for the E brake indicator. I removed the old light socket and spliced the red wire of the LED to the blue wire of the old indicator socket. I spliced the black wire of the LED to the black wire of the old socket. With the E brake on, the LED is bright. When I release the E brake the LED gets a little dim but remains on. I'm not sure what is going on. Any thoughts? Thanks

[MoparLeo]

Find out what you are doing before you start cutting wires. JMO.

[chargerdon]

I would suspect that the Parking brake switch is defective and leaking a small amount of current even when the brake is released.   LED's don"t take as much power. 

Have you tried disconnecting the wire at the parking brake to see if it then goes off completely ??

[Filthy Filbert]

You may have something else back-feeding through the positive wire due to a bad ground elsewhere.   LEDs don't require nearly as much current to illuminate as an incandescent bulb

Get the volt meter out and start testing voltages on the positive feed, and resistance to ground at various components as you trace back through the system.

[Huskidrive]

I had the same problem when I put LEDs in my dash. My problem turned out to be a loose connection on the wire going to the distribution block under the master cylinder.

[money pit]

There's not much to the E brake switch. Either it's grounded, light on or it's not grounded, light off. I'll try cleaning the grounding points. May be the E brake cable is grounding somewhere. Thanks

[money pit]

I haven't tried that yet. If it does, does that mean there's a bad ground?  Thanks

[Dmod1974]

The ground circuit for the Brake Lamp is grounded via 2 things: the Parking Brake switch, and the brake pressure differential switch in the combination valve.  You are most likely getting a poor ground from the latter.  Not enough to light an incandescent bulb, but enough for an LED.  Unplug one or the other and see which one causes it to go out.  That's your culprit.

[money pit]

Thanks.  I'll take a look at it in the morning, If it's the differential switch, will replacing it repair the problem? Or can I just disconnect it?

[Dmod1974]

I believe there is a vendor that rebuilds or sells rebuild kits for the combination valve, but it would be easier to just unplug the darn thing.

[Huskidrive]

https://musclecarresearch.com/1970-76-mopar-combo-valve-rebuild

https://www.manciniracing.com/propbrakval.html

[elan71]

Hi
I have exactly the same situation. Replaced the old bulb with an LED.
I found the problem with the brake pressure differential switch. I installed a brand new one, but the problem is still there. At the moment I have the wire disconnected and the LED stays dark.
I will go back to a bulb to see if this solves the problem. I will also test some other LED brand to see is there any different.

[money pit]

I removed the wire on the differential switch. The light went off.  Thanks

[elan71]

Hi
I tested several different LEDs but no success. I think the brake fluid is somewhat conductive, which triggers this behavior.
So, I go back to a "normal" bulb. Works also fine for me. It is more important to have an indicator if the brakes are not working correctly than a brighter light. I suggest to replace the LED with a old fashion bulb to be safe. Just my thinking.

[Filthy Filbert]

Hi
I tested several different LEDs but no success. I think the brake fluid is somewhat conductive, which triggers this behavior.
So, I go back to a "normal" bulb. Works also fine for me. It is more important to have an indicator if the brakes are not working correctly than a brighter light. I suggest to replace the LED with a old fashion bulb to be safe. Just my thinking.

Except, when you have a leak on one of the brake circuits and the light comes on, you already know it because your foot went to the floor on a spongy pedal and your car isn't going to slow down very well.    at that point, by the time you recognize there's a warning light on, you've already crapped your pants and are looking for places to steer to that will bleed off speed or offer a soft cushion to stop on.