I've read through all the terrific articles willcox provided in the tech section regarding hazard lights and the brake lights and turn signal circuits, but my issue is much more stubborn. I don't have working brake lights on my 73 corvette, nor do the hazard lights work. Turn signals work fine. The tech articles have helped me determine things to test, but the problem still eludes me.

Things I've done:
Pulled brake light switch, tested it, proved OK.
Ran test light to orange wire on the brake light switch connector, lights, but seemed dim.
Jumped brake light switch connector: no lights, but fuse gets "HOT".
Checked ohms from brake fuse holder to hazard flasher terminal, showed 6 ohms, seems higher than I'd expect.
Pulled fuse block and inspected for bad wire from fuse to hazzard: everything looked nice and clean, no scorched wires or corrosion
Ran OHM meter from brake fuse terminal to orange wire on brake light switch connector: less than 1 ohm.
Ran OHM meter from white wire to brake light switch connector to ground: less than one ohm.
- repeated test but disconnected the 'harmonica' connector at steering column (non-tilt), infinite OHMS.
Tested steering column harmonica pins to ground, none go to ground.

I'm running out of ideas and was hoping you had some I haven't tried.

 

I just looked at my 73 wiring schematic and can honestly say That it news to me that the brake switch goes through the directional signal in the column. My guess is that the problem could be with the Directional Switch (Steering Column), since the hazard flasher switch is Not working. If NONE of the lamps (Front / Rear) come on when the Hazard Switch is depressed, that tells me it’s not a ground issue. You can try a new Directional Switch and just plug it in at the Harmonica Connector without removing the steering wheel. Have you looked to make sure the bulbs are correct (two filaments), and the sockets are clean? I believe your Rear Lamp ground is ok, as all the rear lamps use the same black wire ground. If you try a new Directional Signal, it’s imperative to use the Willcox tutorial because the reproduction Switch has different wire colors. I had to change my Directional Switch because after turning the steering wheel, the turn signals would not release. Hope this helps. Good Luck.

 

Without actually bothering to understand why the brake light wiring has to run through the directionals, switching it out fixed an intermittent problem I was having with the brake lights. It's a moderately hard job and not all that expensive. Probably worth your while to figure out why it's wired that way before you decide to do it. For me the evidence was close to incontrovertible, so I did it.


I like the above suggestion of just trying it without doing the install. Didn't think of that myself.

 

Update, ran through these steps I pulled from another thread to test turn signal switch... (Thanks swampeast Mike!). I don't think I have a switch problem:

You'll have to find and disconnect the "harmonica connector" attached to the outboard side of the steering column near the base. Disconnect and make the following tests on the switch (not harness) side of the connector. Whoever is doing this will find it FAR easier if you remove the driver seat!

1) With the hazard light switch "off" (pulled out) and turn signals off check for continuity between the brown and purple wires. You should not have continuity. Turn the hazard switch "on" and test again. You should not have continuity. If you get continuity replace the switch.

2) Turn the hazard switch off again and test between the brown and the light blue, dark blue, yellow and dark green wires in turn. If you find continuity between any of these with the brown wire the switch is bad.

3) Next turn the hazard light switch "on" and test the same pairs. You should have continuity at ALL. If not, replace the switch.

4) Turn the hazard switch back off (blinkers still off). Check for continuity between the purple and the light blue and dark blue wires in turn. If you get continuity the switch is bad.

5) Move the turn signal for a left turn. You should get continuity between the purple and light blue wires but no continuity between the purple and dark blue. If not, replace.

6) Move for a right turn. You should now get continuity between the purple and dark blue wires but no continuity between purple and light blue.

If the switch passes ALL of these tests it is OK and your problem lies elsewhere.

 

Mr Green,

Here is a link to an old post with better wiring schematic, Brake Lights Don't Work, I'm not sure what year its for but it should get you going in the right direction. If I was troubleshooting the circuit this is the diagram I would want, not the original diagram which IMO is convoluted ( I have not seen the Wilcox articles or diagrams and this might be the same as them).
To T/S you need to be methodical and start at the beginning of the circuit and check for 12 V everywhere it should be. Get a test light and hook one end to a good ground and start checking all the wires i.e. fuse in and out, orange wire into brake light switch, white wire out of switch with it depressed keep doing this all the way to the actual light sockets. If you get 12V all the way there then you need to check your grounds, even if they are hooked up you should clean up the connection.
As stated above you might just find out the turn signal switch is bad. I had no idea why the brake lights went through the turn signal switch but after seeing the diagram it shows the logic behind it. If you don't get power out of the green or yellow wire you can double check the switch is bad by jumping from the white wire (or any positive 12V) to either green or yellow to confirm the circuit after the turn signal switch is good. Hope this helps and good luck.

 

Remove the drivers' side kick panel and locate the 12 point connector that brings power to the rear lights, you may have a loose connection.

https://docs.google.com/viewer?a=v&p...ZTM0ZDc1MWM5Ng

 

Testing at the Harmonica Connector proves that your Directional Switch is good. You should probably next test the wiring harness part of the Harmonica Switch. You will need a Schematic that tells where each of 12 wires go. I will attache a picture of the Connector.

 

A couple more steps to verify the brake light circuit through the turn/hazard switch. I'm sure you've checked the brake light switch for proper operation, right?

1) With the brake light switch pressed check for full battery voltage at the white wire on the harness side of the harmonica connector (this if you check with power). Or you can check for continuity between the orange wire at the brake light switch and the white wire on the harness side of the harmonica connector (this if you check without power). If you don't get power/continuity the problem is on that white wire that runs directly from the brake light switch to the harmonica connector.

2) Reconnect the "harmonica". Again operate the brake light switch and check for power at both the yellow and dark green wires on the harmonica connector. If you don't get power the problem is in the turn/hazard switch. If you do get power the problem is somewhere along those yellow and dark green wires (they pass through the connection between the cabin and rear lamp harnesses that will be the largest connector in the general area of above and to the left of the steering column).

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The reason the brake light power lead passes through the turn/hazard switch is that turn and hazard use the same filaments in the tail lamp fixtures and this allows this brake lights to stay steady burning when you press the brake pedal regardless of whether the hazards are on or off.

 

The turn signal contraption switch in the steering column also lets a turn signal blink while the opposite side remains bright if you're on the brakes.

I would start by cleaning all the sockets and replacing all the turn signal and brake lamps. I had a struggle with mine (ages ago) and eventually I ended up replacing the contraption switch in the steering column....been working fine since then.

 

Well it's solved, for now anyway...

Since the turn signals worked I knew I didn't have an issue with bulbs or grounds out back, since as pointed out above, signals not only use the same filaments as brakes, but the same wires as well. Also there couldn't be a short in those wires for the same reason.

The hint to my issue was the resistance from fuse to hazard flasher terminal, which is the first jump to then get to the orange wire on the brake light switch. Although my fuse block looked clean and the fuse tested ok, there must have been enough dust or "stuff" to cause some resistance. With the fuse block out (well, unbolted from the car and main engine side harness removed) and brake fuse removed, I cleaned it up with terminal cleaning spray and hit it with a brush a few times and reassembled. Once all back together, I ohmed it out with the meter and go 0 ohms, then used the test light to the orange wire on brake switch and got a nice bright light. Hooked a brake switch up and viola, brake lights. Thanks for all the helpful suggestions. The test procedures to prove out the signal switch was great. Although frustrating, at least this was a "free" fix, even if it took a few nights to get it done.

 

For the next guy, links to the willcox articles referenced above:
http://repairs.willcoxcorvette.com/1...mp-simplified/

http://repairs.willcoxcorvette.com/1...e-panel-issue/

 

Thanks for the update. I have never removed my fuse box and wonder how much corrosion is on the plug. When I change a fuse a big chunk of the box broke off. Being from the School of Bubba, I used epoxy to reattach the piece. Was it painful to remove the fuse box?

 

The box comes loose pretty easily by disconnecting the main engine side connector at the fire wall (3/8 bolt secures this plug) and removing the two 5/16 screws (top right and bottom left corners). There is certainly some contortionist activities to get to the screws, but a universal socket and a long extension helps. I'm not certain how to get the rest of the harness disconnects from there, but that will get you started.

 

Thanks for providing the followup update on how you fixed it.

 

While it snaps onto it the cabin side connector the fuse box is not a part of the bulkhead connection That connection (one part on the cabin side, two parts on the engine compartment side) is filled with dialectric grease so it's the most corrosion protected connection in the car..

 

Thanks for all the info. Hopefully this will be one of the items that Won’t require fixing😬.