Dash Brake Warning Light Part Number 113919233B

This is to assist others that are having problems with keeping their Brake warning light working the way it should. It goes into the simple theory of operation, and into piece part detail to repair your unit. These units are still for sale, but are easy to repair.

Basic operation is the unit lights up when either a ground is applied from the parking brake handle switch at terminal 61, or a positive voltage is applied to terminal K from the pressure switch(s) on the master cylinder. For this to work a positive voltage must be supplied to terminal 15 of the assembly, and the bulb must be operational.

If you unit stays lit up when you disconnect both connection of K and 61 then your unit is in need of repair, or replacement. Another failure mode is if the light is on, and dims when the brake light is applied

Removal of the unit from the dash is simple, place a small flat blade screwdriver at the 3 and 9 o’clock position on the front of the dash and push it out. You will see the wires to the terminals going to the back of the assembly. To test the bulb, apply positive voltage to terminal 15 and negative voltage to terminal 61, and the bulb should light.

If you want to take the unit apart there are two tabs holding it in. Push these tabs and slide it out. Don’t let what you see scare you, all these electronics are easy to get at Radio shack. Two resistors, two diodes, and a transistor. The resistors are the bigger round devices, with squared off ends one is a 670 ohm resistor, and the other is an 82 ohm resistor, with the colors gray red and black on it. The other two are diodes; the black mark is the "blocking" side of the diode. The device with three legs is the transistor, a NPN type. As you can see with the unit disassembled terminal 15 is just the positive side of the bulb.

Now to troubleshoot what is wrong with the unit, you can take a meter and do a diode check on the diodes, and if it has continuity both ways it is bad. , De-solder and replace with an appropriate rated diode. The transistor on the other hand has to be removed to be checked, on those terminals on your digital volt meter that you may not use often, so you may need to read the owners manual to see how to do that test. Once you know which component is bad, simply de-solder and replace. If you are replacing the diode, remember to put the black stripe on the same side it came off.

Reassemble and reinstall. I have found that the Parking brake switch contacts get a bit corroded over time, and you can remove that unit, and scrape away the corrosion, and it should work.

Disassembled, diodes, resistors, NPN transistor

Unit made with a breadboard, yep too big to put behind the dash.

Crude drawing of the assembly