5 replies to this topic

[ImagoX]

I'm baffled guys and could use some help...

 

After installing a new engine (long story), I was hooking up electricals and noticed the brake light switch on the brake pedal in the cabin was broken. Ordered a new one and went to look for the wires but I can't find them (what the hell?).

 

According to the Haynes diagram, the lead INTO the switch is a switched green lead that goes into the cabin straight from the fuse block, and the electrical current OUT OF the switch is carried to the tail lights by a green/purple wire. Right now NEITHER wire is connected since I can't find either one.

 

Here's the thing... when I switch on the ignition MY BRAKE LIGHTS ILLUMINATE. According to the diagram, this is impossible, since the only way for current to flow into the green/purple stop light wires is via the brake switch.

 

I checked the tail lights by switching the ignition off but then turning ON the main headlight switch and as expected the tail lights (not the brake lights) illuminated. Switching on the ignition immediately illuminated the stop lights, like there's a direct connection between the hot, switched green lead and the green/purple (which I can't see how happened).

 

I tried tracing the wires from the tail/brake lights back forward, but they go up into the LH rear a-pillar (behind the gas tank) and I cannot follow them. It appears as if the green/purple wire reappears on the LH side via the front a-pillar hole and then passes through the firewall right near the wiper motor. Beyond that all the wires are wrapped in tape and can't be seen.

 

Ideas? I can snip the green/purple wire up front near the a-pillar and then splice in a new lead to the brake light switch (along with a second, green lead to the switched hot), but I hate the thought of having some weird, random (possibly still hot and short-able) connection somewhere inside the harness...

 

Thanks! --Matt

Edited by ImagoX, 23 November 2014 - 01:17 AM.

[Craig89]

Hi Matt,

If there's no sign of the other end of the cable anywhere then I would start unwrapping the loom

Edited by Craig89, 23 November 2014 - 06:29 AM.

[Spider]

It didn't get puuled up behind the instrument cluster did it?  It will be there somewhere!

Edited by Moke Spider, 23 November 2014 - 08:29 AM.

[Dan]

Check that your car doesn't have a hydraulic brake light switch in the engine bay at the brake line tee piece.

[dklawson]

I saw you also posted this on the MM board.  My thought was like Robin's (Zippy's) on MM and Dan's above.  It sure sounds to me like you have a later pedal box on a car where the original brake light switch is hydraulic.  

 

You said the brake lights come on as soon as you turn the ignition key to run.  That sounds like a failed hydraulic switch.  As mentioned by Robin on MM, look for the switch on the subframe below and behind the clutch cover.  It will be on the brake pipe in the T piece that Dan mentioned above.  If your car has been converted to use DOT-5 (silicone) brake fluid, there is a very good chance your hydraulic switch has failed.  It's a fairly common occurrence with DOT-5.  While you could fit a replacement hydraulic switch, that is not a long-term solution as the switch will fail again.  Instead, if you find the hydraulic switch on the brake pipes, make extensions for its wires and run them back to that new pedal box mounted switch you installed.  

[ImagoX]

Derp de dur... I got it. Here's what happened:

 

Apparently when I broke the old switch (yes, I absolutely have a white, plastic switch bolted to the brake pedal assembly that actuates the stoplights) I snapped clean off the top half (with all the electrical connections) and left the plastic half with the plunger behind on the pedal. Then, when I lifted the cabin heater box, I trapped the (still connected) top half of the switch on top of the heater box - that's why the circuit was complete. I was thrown off by the presence of a green/orange wire with the correct terminal plug - I figured that was one of the wires and the diagram was incorrect (as I've heard can happen) in the Hayne's book aka "The Blue Book of Lies". It wasn't. I don't know WHAT that wire goes to yet, but it's not part of the brake light circuit.

 

I dug around on top of the cabin heater box, located and retrieved the broken plug, found the green and green/purple wires and connected them to my new switch and all is well - thanks so much!!!