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Brake light help

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Get a Volt meter - they are cheap ($3.49 at Harbor freight right now - though I might splurge on the $10 one)

You can't do this kind of diagnosis without one - it's a must have for old cars. Set it to 20 volts, turn it on and start reading. Part of the reason you want one is not just if there is current but how much there is. Less than 12 volts (or 11.4 or whatever shows up) can light a cheap tester but not a real bulb.
 
If he got power across the switch when he pushes the pedal the flat is between the switch and the brake lights.

Check for power at the lights. If no power therer, you could run a new wire from the switch to the rear just as a test.
 
jlaird said:
If he got power across the switch when he pushes the pedal the flat is between the switch and the brake lights.

Check for power at the lights. If no power therer, you could run a new wire from the switch to the rear just as a test.
Click to expand...

Not sure what "flat" is, but read back his posts carefully.
No power with tester on either wire (green or green/purple) at the switch.

If absolutely true, he has a problem before the switch.
And, with all the issues of charge, ignition light on, and other things, disturbing the wires at the fusebox is not at all out of the realm of possibilities.
 
jlaird said:
If he got power across the switch when he pushes the pedal the flat is between the switch and the brake lights.
Click to expand...

he didn't get power Jack, he got continuity
 
Well, I am pretty sure I burned out the bulb in the continuity tester. I forgot to unhook the power when I last tested. Before this happened though, here is what I found:

1) There is power between the fuses.
2) The brake switch shows continuity.
3) When I hook a wire from the terminal with two green wires on the fuse box to the green wire post on the brake switch and press the brake pedal I get brake lights.

That tells me there is no power between the fuse box and the brake switch, correct? I rechecked all connections, and they are fine. I am baffled. I thought maybe the fuse box was bad, but that wouldn't make sense since the other green wire attached to the same post powers the heater switch and it works fine. Suggestions?
Kevin
 
Oh, no power to switch, so run a line from battery to switch and test from there.

Hard to do this from long distance, so easy when in my garage. sigh.
 
ichthos said:
Well, I am pretty sure I burned out the bulb in the continuity tester. I forgot to unhook the power when I last tested. Before this happened though, here is what I found:

1) There is power between the fuses.
2) The brake switch shows continuity.
3) When I hook a wire from the terminal with two green wires on the fuse box to the green wire post on the brake switch and press the brake pedal I get brake lights.

That tells me there is no power between the fuse box and the brake switch, correct? I rechecked all connections, and they are fine. I am baffled. I thought maybe the fuse box was bad, but that wouldn't make sense since the other green wire attached to the same post powers the heater switch and it works fine. Suggestions?
Kevin
Click to expand...

yes, so, tomorrow when you get your new continuity tester, the first thing you are going to do is check for continuity on that one line - power off - one end at fuse terminal, the other end at the green wire by the brake switch. If there is no continuity as we suspect, then it can only be one of two things.

1. one of the ends is loose or corroded or,
2. there is a short in the wire.

Give both ends of the wire a good clean - and even wiggle or pull to see if they are loose.

If it is the wire, you may find it easier to either run a new wire of pull a green feed from elsewhere rather than open the harness. I had the same problem actually and just spliced into another green wire from the same fuse. Of course with a '76 there are many more wires to choose from.
 
Geez, JP, put the sermon down for a bit.....

That's what I've been saying.
His original test (where I came up with "all stop") showed no power to the switch.
I have been trying to get him to look at where the brake light wire connects to the fusebox.

We've been in that area before, with the charging issues, ignition switch, ignition light on all the time.....

The "continuity" was later, and a red herring, as he previously had found no power to the switch.

I knew what I was saying.
 
I knew too. :cheers:
 
I will be stopping by the harware to get a new bulb for my continuity tester tomorrow. When I get it working again,(and I have he power shut off this time) I am going to disconnect the green wires to the fuse box and switch and test the continuity of this wire, correct? I have already checked connections, and they look fine. This was a brand new harness, and I really haven't fiddled with this area much. I am suprised to find a problem in this area, especially since the brake lights were working to begin with. Buy the way guys, thanks for helping me out. At the very least, now I can hook up a temporaty wire so that I will have brake lights for my trip to get a front end alignment Saturday. If things go well, I may even get time to put on my doors this weekend.
Kevin
 
JPSmit said:
[
yes, so, tomorrow when you get your new continuity tester, the first thing you are going to do is check for continuity on that one line - power off - one end at fuse terminal, the other end at the green wire by the brake switch. If there is no continuity as we suspect, then it can only be one of two things.

1. one of the ends is loose or corroded or,
2. there is a short in the wire.
Click to expand...

I'm not sure this is right. Doesn't the fusebox feed the ignition switch which then feeds the brake lights? If so, then it could be a problem with the switch connections under the dash, or a problem with the ignition switch.
 
ichthos said:
I will be stopping by the harware to get a new bulb for my continuity tester tomorrow.
Kevin
Click to expand...

If you have the same cheap tester as mine, it's cheaper and easier to replace the whole unit than find the bulb that fits.
 
I will take a look at the wiring diagram again when I get home, Davester. The switch has been a problem (The switch and lock barrel are new), as TOC has mentioned, but I did check it with the continuity light, and it seems to be ok after I worked the lock barrel a little. I do have to use a little pressure to push the key in when turning it on or off. I have a NOS switch that I recently purchased off of Ebay. I have to check it with a continuity light when I get home, but it seems work much better in that the lock barrel turns smoothly and no pressure is needed. I may just do a swap and see what happens. I will still be checking the green wire for continuity when I get home tonight as JP suggested.
Kevin
 
obviously if the wire goes through a switch - the switch will need to be open for continuity - battery disconnected then if you are checking with a continuity tester or not if with a multimeter.
 
The ignition switch feeds the fuses through a white wire. The green wire from the other side of the fuse goes directly to the brake light switch. There is no other switch between.
 
You got the easy part of the job left, well done.
 
Here is a part of the BE wiring diagram.
A3 supplies 12V from the switched side of the ignition switch (white).
The fuse is between A3 and A4 and is jumpered internally at the fuse box over to the second A4 terminal (let's call that A4(2)).
If the car is wired per the schematic (how do we know?), A4(2) which is green supplies the switched 12V to the brake switch (#31)(about 12" away).
The second A4(2) (green) wire travels into the dash area and supplies the Heater switch (#34) and fuel gauge (#36)and the windshield wipers (#46 off the page).
A4 is a single green wire and it supplies switched 12V to the flasher unit for the blinkers (#38).

Kevin has said that he checked all the wires at the fuse box.
If I was to bring out my big crystal ball and hazard a guess what is wrong, I would say that only the brake switch wire is connected to A4(2) and the other two green wires are connected to A4, AND the problem is that the internal connection in the fuse box from A4 to A4(2) is suspect!
With the right understanding of electricity and the wiring diagram, and a VOLTMETER Kevin, this is as easy as it gets to troubleshoot. You don't even have to go under the dash on this one! If this is too technical, excuse me as I R A engineer.
Scott in CA
 

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I bought two bulbs for my continuity tester on the way home, but the kids wore me out at work today. I crashed as soon as I got home. Scott, can I translate what you said for me? Aren't you still saying to check the continuity of the green wire for the brake lights by hooking up my tester to the green wire only at the fuse box and the green wire at the brake switch? By the way, I have the heater wire and brake light wire hooked into the same post on the fuse box as this looks like what I am supposed to do if I am reading the wiring diagram correctly.
Kevin
 
Problem solved! As TOC and JP speculated, it was the fuse box. Specifically it was the connection between the two A4 terminals. The A4 terminal to the outside does not work. The way I found out is I connected each of the three green wires to the first A4 terminal one at a time, labeled each, and all worked. I then connected each to the second A4 terminal and none worked. I don't know how the fuse box could work and then all of a sudden not work, but luckily I have a spare fuse box somewhere I will put in if I can't figure out what is wrong with mine. In the mean time, I have all three green wires into the first A4 terminal and everything works. Not happy about all the time I spent, but on the other hand I learned a little more along the way. Thanks again everyone.
Kevin
 
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