Steering column connections and lighting: FIXED

[SteveJ]

Pull the 20A fuse. Turn the headlight switch to off.

Measure resistance (not continuity) from the left terminal of the fuse to each wire on the parking light side of the headlight switch. One wire should have about 0 ohms (probably the green/blue), and the other should have a lot more (probably the green/white).

Measure resistance to ground on the wire that had the higher resistance in the first measurement. It should be low now.

Unplug the two connectors indicated below and repeat the resistance measurement.

If the resistance is still low, the short is in the dash harness.

If the resistance is high, plug in the larger 6 pin connector and re-measure. If the resistance is low, start checking the front markers and the front side markers. Unplug the connector again. Plug in the small 6 pin connector and re-measure. If the resistance is low, start checking the rear markers and rear side markers.

Let us know what you find.

[BoldUlysses]

Hi Steve.  OK, so:

• I have the multimeter's dial set to 200 ohms.
• The only wire of the 4 on top of the combo switch with any resistance at all is the green/white one, and it stabilizes at 0.5 ohm.
• There is no resistance between the green/white wire and ground.
• There is a resistance of about 0.7 ohms between green/blue and ground.

Unplugged connectors, results:

• Resistance between green/white and ground: 0.
• Resistance b/t green/white and left terminal of fuse: 0.7 ohms.

Plugged larger 6-pin back in:

• Resistance b/t green/white and ground: 0
• Resistance b/t green/white and left terminal of fuse: 0.7 ohms.

In other words, it doesn't seem to make a difference, resistance-wise, whether or not the two 6-pin connectors are plugged in, which I assume means the short is in the dash harness.  Which probably means, as expected, that I have something hooked up incorrectly.

Anybody with a '72 feel like pulling off the column covers and snapping a pic or three of all the wires and connectors?

Thanks again.

[emccallum]

Not sure this will help, as I may be in your situation later on! I thought I took pictures of my steering column but I couldnt find them. 

I did put them together on the bench. There is a black wire that connects the headlight switch to the blinker switch. I cant tell if you have that one connected. 

 

[BoldUlysses]

^Thanks!  That does help confirm a few things, like the fact that the blue/white wire from the combo switch connects to the black wire on the dash harness (always unsure when wires change colors like that).

The short black wire from the turn signal switch to the combo switch is connected.

I haven't had much time in the past few evenings to continue troubleshooting, but last night, I jumped the red/white and green wires on the combo switch, and the parking lights & dash lights came on, albeit dimly, without popping the 20A fuse.

This indicates two possibilities to me.  Either:

1. The short is in the combo switch, or
2. My jumper wire is too small to carry the full 20A and protects the fuse.

Either way, this weekend I'm going to pull the two switches off the column and go through them with a fine-toothed comb.

[SteveJ]

50 minutes ago, BoldUlysses said:

^Thanks!  That does help confirm a few things, like the fact that the blue/white wire from the combo switch connects to the black wire on the dash harness (always unsure when wires change colors like that).

The short black wire from the turn signal switch to the combo switch is connected.

I haven't had much time in the past few evenings to continue troubleshooting, but last night, I jumped the red/white and green wires on the combo switch, and the parking lights & dash lights came on, albeit dimly, without popping the 20A fuse.

This indicates two possibilities to me.  Either:

1. The short is in the combo switch, or
2. My jumper wire is too small to carry the full 20A and protects the fuse.

Either way, this weekend I'm going to pull the two switches off the column and go through them with a fine-toothed comb.

No, you're not on the right track.

When you jumpered over the red/white to the green, you bypassed any fuse protection outside of the fusible link. If you're not putting any current through the fuse, it won't blow. I hope you didn't have an electrical fire.

On 5/3/2022 at 8:46 PM, BoldUlysses said:

Hi Steve.  OK, so:

• I have the multimeter's dial set to 200 ohms.
• The only wire of the 4 on top of the combo switch with any resistance at all is the green/white one, and it stabilizes at 0.5 ohm.
• There is no resistance between the green/white wire and ground.
• There is a resistance of about 0.7 ohms between green/blue and ground.

Unplugged connectors, results:

• Resistance between green/white and ground: 0.
• Resistance b/t green/white and left terminal of fuse: 0.7 ohms.

Plugged larger 6-pin back in:

• Resistance b/t green/white and ground: 0
• Resistance b/t green/white and left terminal of fuse: 0.7 ohms.

In other words, it doesn't seem to make a difference, resistance-wise, whether or not the two 6-pin connectors are plugged in, which I assume means the short is in the dash harness.  Which probably means, as expected, that I have something hooked up incorrectly.

Anybody with a '72 feel like pulling off the column covers and snapping a pic or three of all the wires and connectors?

Thanks again.

Your description of the results are confusing. Are both wires on your switch green/white?

The resistance between the switch and fuse should be almost 0. With 0.7 ohms, it says dirty connection. Having the other side of the switch be 0 ohms to ground indicates a dead short.

Disconnect the 6 pin connector at the steering column. On the dash harness side of the connector, measure resistance to ground on the green/white and green/blue wires.

 

[BoldUlysses]

13 minutes ago, SteveJ said:

No, you're not on the right track.

When you jumpered over the red/white to the green, you bypassed any fuse protection outside of the fusible link. If you're not putting any current through the fuse, it won't blow. I hope you didn't have an electrical fire.

I'm confused (clearly).  Isn't that what the switch does anyway?  Connect the red/white and green wires to provide power to the parking lights when the switch is in the correct position?  And if there's a short in the switch, couldn't it be allowing too much current into that circuit?

Quote

Your description of the results are confusing. Are both wires on your switch green/white?

The resistance between the switch and fuse should be almost 0. With 0.7 ohms, it says dirty connection. Having the other side of the switch be 0 ohms to ground indicates a dead short.

Disconnect the 6 pin connector at the steering column. On the dash harness side of the connector, measure resistance to ground on the green/white and green/blue wires.

No, it looks like the image above:  The middle wire is green/blue and the top wire is green/white.

Will disconnect the 6 pin tonight and report back.

[emccallum]

here is another picture I found searching the net.

 

[SteveJ]

18 minutes ago, BoldUlysses said:

I'm confused (clearly).  Isn't that what the switch does anyway?  Connect the red/white and green wires to provide power to the parking lights when the switch is in the correct position?  And if there's a short in the switch, couldn't it be allowing too much current into that circuit?

For the parking lights, the switch connects the green/blue and green/white wires together. In the fuse box, the white/red wire connects to the "high" side of the fuse. The green/blue wire connects to the "low" side. When everything is connected, you will have battery voltage on the headlight switch at the green/blue wire. When the switch is turned to position 1 or position 2, the green/blue is connected to the green/white. to send voltage to all of the bulbs.

I suspect that you could see dim light in your parking lights when you bypassed the switch because there was enough current to flow through the bulbs as well as the short. If you jumpered the wire at the combo switch, you bypassed all fuses as the power for the headlights goes through the switch and out to the fuse box (That is the opposite of how the parking light circuit is wired.).

If you saw 0 ohms from a wire to ground in the tests I described a few days ago, that indicates a dead short. Disconnecting the connectors in the passenger footwell was an effort to try to narrow down where the short could be. If the resistance went up after disconnecting part of the harness, you can reasonably expect that the disconnected harness is shorted somewhere.

 

 

[BoldUlysses]

8 hours ago, SteveJ said:

Disconnect the 6 pin connector at the steering column. On the dash harness side of the connector, measure resistance to ground on the green/white and green/blue wires.

OK; I did this.  0.7 ohms from green/white to ground, 0 ohms from green/blue to ground.  Harness side of the connector.

Car off, key removed, 20A fuse pulled.

7 hours ago, emccallum said:

here is another picture I found searching the net.

 

Thanks for that.  Your Google-fu is stronger than mine.  That helps confirm a couple of connections.

Edited May 6, 2022 by BoldUlysses

[SteveJ]

1 hour ago, BoldUlysses said:

OK; I did this.  0.7 ohms from green/white to ground, 0 ohms from green/blue to ground.  Harness side of the connector.

Car off, key removed, 20A fuse pulled.

Are you sure it was 0 ohms from green/blue to ground? That would indicate a short between that connector and the fuse box. In other words, I would expect a fuse to blow as soon as you plug it into the fuse box.

Go to the left side of the parking light fuse in the fuse box and check resistance from there to ground. Also make sure the back side of the fuse box is not making contact with the body of the car.

[BoldUlysses]

Sorry.  OK.

From the top of the combo switch, 0.7 ohms from green/blue to ground, 0.7 ohms from green/white to left side of parking light fuse. 

What makes it even MORE confusing is the fact that the wires change color as they pass through the 6-pin connector under the steering column:

Right side is up to the combo switch, left side is into the dash.  Notice how the green/blue on the right changes to green/white on the dash harness, and the green/white from the combo switch goes the other way.  That's probably why the last round of measurements seemed backward.

I swear I haven't rearranged the pins, and the car never had any electrical gremlins before the restoration process started.

In any case, I'm totally stumped now.  Anybody want to drive up and help me sort this out?  I'll pay for gas and a 6-pack of your choice...

Edited May 7, 2022 by BoldUlysses

[SteveJ]

When tracing wiring go by the colors in the wiring harness. That is what the wiring diagram is based upon. The fact that the switch switched the colors doesn't really matter much as long as you keep the wiring harness colors straight. 

I don't have the spare time/energy to drive up to Chattanooga, but if you want to drive a couple of hours down to me, I will give you hands on training in using a meter to diagnose using my 73. The connectors are different, but the wire colors of the affected circuit is the same as your 72. Once you get the technique down, it should be easier to find the short.