Unfortunately, I was pulled over yesterday by a cop (issued with a warning, phew!) and his reasoning was that my 3rd brake light was not working. My high mount brake light (third brake light) is apparently not working, even after I replaced the bulb. The bulb I bought at the auto parts store does not look exactly the same, but does have the same numbers and general shape. I'm wondering if the plastic connectors might be bad? Do I have to replace the entire assembly or wiring?

 

Have you checked to see if there is power going to it at all?. If not trace back the wiring as it goes thru the center of the roof to the front and down the driver a pillar. there is a connection down there. I think under the dash. See if thats connected as well

 

I changed the bulb and it didn't look like anything had melted around the socket. But the upper brake light still doesn't work. I wedged a 2 x 4 between the front of the seat and brake pedal to activate the brakes and I didn't see any power at the terminal on the third brake light socket or the terminals prior to transitioning into the phone-chord like spiral wire. The regular brake lights work fine. From reading other posts here, I understand there's a separate stop lamp switch for the third brake light. Anyone know if both these switches are for brakes or is the third brake switch mechanism integral to the main stop lamp switch?

 

OK, see to the left of the blue housing connector (1st pic). The ORG, LT BLU, and YEL wires. They are for the brake lights.

Orange is battery power to the switch.

Light blue goes to the left & right hand side (regular) brake lights.

Yellow goes to the high mount brake light.

Internally the brake pedal switch has two sets of contacts. Also, the light blue & yellow wires go to the back of the car via two different intermediate connectors. C214, for the high mount light, is at the base of the left side windshield pillar. It is a 4-position connector. The wires go up the pillar, then along the roof to the rear of the car.

RBob.

 

Thanks for the information. My next step will be to see if I'm getting power from the yellow wire with the brake pedal pressed.

 

Another easy test is to unplug the connector from the brake switch. Then jump the orange wire terminal to the yellow wire terminal. That should turn on the 3rd brake light. No need to even do a key-on, the brake lights get fed from battery power.

Can also jump orange to lt blue and note that the main brake lights illuminate...

RBob.

 

What year is your car? If by high mount, are you referring to the light inside the hatch, there is a common problem with those lights. Verify that the tabs are actually making proper contact with the bulb. I've fixed a few of them by doing that..

 

It's a 1992 and the light is on the inside of the hatch window at the top. I checked for voltage on the socket, even tried moving the bulb around in the socket to see if that might be it, but still no illumination.

 

I was able to follow the excellent advice of @RBob and jumpered the orange and yellow wires on the stop lamb switch with a paperclip. The result was illumination of the high-mount brake light! I exercised the switch with the brake pedal depressed and extended the center shaft repeatedly but it didn't fix anything. So it looks like the switch itself is bad. Also, when I jumpered the orange and light blue wires I got the regular brake lights. Anyone know the part number for this switch?

I didn't pull the connector plug from the switch. The plug has hinged tabs on both sides and I was able to open them with a small screwdriver to expose the terminals for purposes of jumpering the wires, but the plug itself doesn't seem to want to come off the switch without forcing it. Does the black part pull out of the white part or does it separate further up? I'm trying to avoid breaking it. Thanks!

 

This is just a follow-up to my post above. I found the brake switch at Autozone for $27.99. The Duralast part number is DR495. I was glad to see it was made in Taiwan--not China. I took a picture of the original switch (Delco?) showing part number 25529860 but I would be surprised if it was even available from the dealer. The plugs going into the switches have tabs on the flat side and both came out easily using some needle nose pliers to press down on the tab while pulling it straight out. The threaded end of the switch pulls right out of the retaining spring plate, allowing easy replacement. It took about 15 minutes to install the new switch.

 

ADDENDUM: I took the old switch apart and what appears to have worn out are the two metal spring tabs that touch the brass tip of the center shaft as it moves with brake pedal movement. I suspect the contacts on the three-pronged switch have corroded too. This would explain the failure of the upper brake light but not the regular brake lights. After 31 years of use, I wonder how many times that switched has moved. You can see the three-pronged switch contacts in the open and closed position. Thanks for the help on this @RBob and @blacksunshine'91.

 

Can see in this pic the lower right contacts (the discs) aren't even making contact. And they should be to turn on the 3rd brake light. Definitely something is broken in that switch.

But as you say, after so many years and miles, it is bound to have worn out.

RBob.

 

[/QUOTE]

What is the blue plug for?

 

Cruise control, brake input to CC module.

RBob.