Tailight issues

[deadflo]

I suddenly lost my tail and running lights, and dash lights in my 71. I still have headlights.

Brake lights and turn signals still work as well.

Fuses appear OK,and I guess its a ground or wiring issue. Where should i start to check?

Can someone give me a real basic over view of using a test meter to check wiring?

Also, I notice my headlight switch feels different as well. Used to take a bit more force to turn lights on, now it seems real eassy. i wonder if its a sign the switch itself is bad?

[hls30.com]

Re-check your fuses! One of them is more than likely the culprit-you have narrowed to one circuit.

Will

[EScanlon]

Did you do something recently with the rheostat for the lights?

How about getting into the center console and disconnecting a Red and a Red/Green pair of wires from another connector?

Lastly, does your horn still work?

All those derive power from the same wiring circuit.

2¢

Enrique

[bpilati]

I understand there is a ground connection above the gas tank that tends to corrode. I believe they fixed this my car by putting a ground wire inside at the back of the rear deck. The ground connection added is behind the rear interior panel.

[seerex]

If you have lost all like Enrique suggests I would pull the fuse box and examine the back, clean and pull all the fuses if the connections look greenish or check to see if they might be loose.

[beandip]

When you check the fuses don't just look at them , check with a mulitmeter. They may not look burned but check any way , you may save a lot of unnecessary work.

[deadflo]

Ok, I need a bit more advise on the actual testing with a meter.

Enrique, when you refer to those wires are you saying to test the connections to the fuse box? Sorry if I am slow on the uptake. I am not real familar with a test meter. I had an old beater one I used to test resistance on speakers, butknow very little about other circuit testing.

BTW, the horn is still working.

[EScanlon]

{Sorry for the length of this post (one of my typical long ones), but read the top part through and the footnotes only if you need them. Enrique}

The next thing to do is to bypass the Dimmer Switch.

Go to the Dimmer Switch, to the side of the Steering Column. Find the wires going to the Dimmer Switch, the pair should be: Green/White* and Red/Blue*

Disconnect AT the switch and join the two wires that go to the wiring harness.

Start your car (so you don't drain the battery while testing) and turn on the lights. If this resolves the tail light and instrument light problem, then your dimmer switch needs replacing or repairing(1).

If this didn't clear it up, let's bypass the combination switch and see if the problem is there.

The Horn Relay is mounted on the driver's side Kick Panel. There are 3 wires leading to it. Disconnect the Green/Black* wire and connect with a shunt wire (plain wire with the ends stripped) to the Green/White* going to the dimmer switch. Press and hold the horn pad ON. If this turns on the lights on the dash and both tail and running, then your problem is definitely in the combination switch wiring.

Remove the Steering Column Shroud and observe and if necessary, mark any connections so that you can re-connect properly later (2). Disconnect ONLY if you cannot look at, and access the back of the combination switch solder points after removing the screws that hold the switch to the column.

Look at the switch at the base of the Light Stalk. On the back you should see where a Green/Blue (GB) and Green/White (GW) wire connect to it. Check that both wires have a good connection and have not come loose or OFF the solder point. If they have, re-connect them and see if that cleared the problem up.

If the connections are good, connect the GB wire and the GW wire with a jumper wire. Check if this has resolved the problem. If it has, then your switch is bad. You can either replace the whole combination switch, or the individual light circuit switch, or take it apart for cleaning/ repairing.

But that's another post, and hopefully your problem by now will be resolved.

Enrique Scanlon

* Standard Wire Notation: {Color of Body of Wire} / {Color of Stripe}

(1) To repair the dimmer switch, remove from the dash. This is very tricky and some people have found it necessary to remove the DASH to get to it. The switch is held to the main metal frame of the dash by two Phillips Screws. The switch is placed into it's opening hole on top of the frame and then is screwed down. This means that you must access the screw heads from above the switch. This is the tricky part, as directly above it is the Tach. If you have a 90° Phillips (short) you can do it, but it is difficult to align the bit with the head. I found that a Ratcheting 90° combination (Phillips one side, Standard Blade on the other) worked best for me.

Once out, look at the SPRING that has been imbedded in the bakelite. If there are any breaks in the wire, it's easiest to replace than repair. If you insist on repairing, you must bridge the gap in the spring. Soldering will work, but you must be careful that the final bead of solder does not stick up above the main edge of the spring.

Next look at the swipe plate. That's the metal washer with the "hand" (as in a clock) sticking out and making contact with the spring (above). If it is NOT making contact, gently bend it downwards at the angle point just past the flat center portion. Bend it enough that it makes soft but firm contact. Actuate the switch several times and observe that the swipe plate makes contact on the spring throughout it's travel. It might help to lightly scuff the top edge of the spring in the bake lite to ensure good electrical contact for the Swipe Arm.

Lastly, check the contact at the center of the switch, Make sure that the Swipe Arm has a good contact to the connection wire.

(2) As a note for those of you who might be interested in how to "mark" or "tag" your wiring harness easily, quickly and with a LOT less grief than other methods.

Dymo© makes a new labeler, the Letra Tag©. This is a thermal labeler using paper or plastic tape with an adhesive back. It has a keyboard on the face with special characters and 2 line capability. It runs off 4 "AA" batteries, and it's tape is inserted via cartridge.

I've been using it to print a series of letter tapes that I then insert on each side of the connection. I'd been doing this with Masking Tape and pen, but it can get tedious and sometimes impossible to read later because the masking tape gets gunked up.

What I do is have the labeler produce 2 labels, each about an inch long (on mine 6 characters in double line and 5 in single). Remove the adhesive from the back on one, apply to one side of the connection, and do the same with the other label on the other side of the connection.

You can now safely disconnect that wire and you will be able to re-connect it correctly later.

Although this may be over-kill for some of you who are absolute geniuses at remembering where and how every wire goes, it helps those of us who are aflicted with "Now, how did this go?" itis.

To simplify things, just use a SINGLE character repeated as many times as necessary to fill that inch. Since the labeler will allow you to "save" the last label you printed (it stays in memory as long as the batteries are in the unit, or you clear it), you can readily keep track of what the next letter to use is.

I start with AAAAA, key the Print Button and CUT the tape. Repeat and I have the two labels I need. I can allow the machine to shut off (battery save) or erase and print BBBBB. I keep this up for EVERY wire CONNECTOR in that part of the circuit. By the time I've disconnected every connection, I have it properly labeled for re-assembly.

When I'm in a situation that I need more than just the letters to describe / identify a wire or connection, the second line feature allows for space.