(Cab Electrical) Anyone Know What This Is?

[Boydness]

Having problems getting the electrical sorted out. The Headlights and tailights now refuse to work. I have a custom bed on the back with just 4 trailer style circle red lights (2 on each side).

I have a single black line hanging unconnected from the "C" shaped wiring loom, and a Dark Green and a Red cable from the fuse block(out the side) unconnected. I believe that all 3 connect to the same component.

I used the wiring diagram to figure out what the mystery cables from the fuse block were suppose to be connected to(I think), but have no idea what it is?

I highlighted the area surrounding the component in yellow.

Any ideas?


Boyd

[cdowns]

the horn relay/ red black and dark green wires

[kwmech]

Make sure the 4 wire grommet connector at the firewall has not come loose or undone, usually above the gas pedal, this feeds the rear lites. Head lamps could be the dimmer switch. Or how about the headlamp switch itself--power to, unplugged ?

[Boydness]

Originally Posted by kwmech

Make sure the 4 wire grommet connector at the firewall has not come loose or undone, usually above the gas pedal, this feeds the rear lites. Head lamps could be the dimmer switch. Or how about the headlamp switch itself--power to, unplugged ?

I checked it and plug it back in, and at some point after checking all the connections and re-wiring the lines to the brakes, all the lights (except for the far right light) does not work. Although the far right light barely blinks (when the left blinker is suppose to blink)...

Boyd

[Boydness]

Today's Progress:

Started today with just the front marker lights and the passenger light blinking for the driver's side turn indicator.
Assumed that the issue was probably ground related with the 4 trailer-style red round lights installed on the rear of the bed.
Removed and cleaned up the ground portions for each of the lights. 1 on each side was metal and the other was plastic with a grounding strip stretching between 2 holes.
Finally got all four tailights to work (with the dash light switch rod pulled), although I did have to massage (read: Hit) the outermost driver side light until it worked.

Tried just the blinkers next.
Driverside(Left) Blinker worked both front and back, Passenger (Right) Blinker refused to work unless I turned the steering wheel slightly clockwise, but still no dash arrow indicator for it (possibly bad bulb?). Hazards worked and flashed both sides.

Then noticed that the blinkers refused to work when the headlight switch was engaged. Headlight switch off, no problem with blinkers.

Took another look at the fuses and the sorry condition of the patched cables running to the brake light switch. One of the cables came out of the splice. Tried to connect the two wire together to bypass the brake light switch: nothing.

Thought that I would try the headlight switch again with the taillights. Now no tailights, but HEADLIGHTS now worked. Noticed that I also lost the front marker lights as well.

Repaired the cables to the brake light switch. Remembering that the brake light also shared a connection with the cab's rear courtesy light, I unplugged the connection, as there is no installed light/light assembly up there.

Currently:
Front Headlights: Yes
Front marker Lights: Yes
Taillights (w/ headlights): Yes
Blinkers (w/o headlights): Yes
Blinkers (w/ headlights): NO
Brake Lights: NO
High Beams: (Where's The Switch?)
(ADDED) Hazards: NO

Only the Driverside Turn Indicator blinks and the only other working dash light appears to be above and to the right of the Fuel Gauge. Might be bad bulbs.

Note: Have not replaced the missing Horn Relay yet.

OK, someone please tell me that it is a bad relay or something that will correct the issue.


I think that I remember the order in which everything happened while troubleshooting. The only blown fuse was the one for the wipers (bottom most to the right, had a blown 30A in it).
Any ideas? (Drive it off a cliff, sell it for scrap, etc.?!)

Boyd

[69TowRig]

Check the fuses (obviously). While sorting out my electricals I made a few mistakes (shorts) with the battery still connected. BUZZ!!!

I recently had a problem with my rear lights not working. Turned out to be the connector into the dash circuit board. I unplugged it, cleaned and dielectic greased, then plugged it back together. Works great now.

[postjack]While we're on the subject of wiring diagrams, my '69 diagrams I got from GMC Paul's did not have the front body harness or engine harness, so I don't have the wiring diagrams for the lights, regulator, alternator, etc. Anyone know why they wouldn't be in that booklet, or where I can get them?[/postjack]

['68OrangeSunshine]

Originally Posted by 69TowRig

[postjack]While we're on the subject of wiring diagrams, my '69 diagrams I got from GMC Paul's did not have the front body harness or engine harness, so I don't have the wiring diagrams for the lights, regulator, alternator, etc. Anyone know why they wouldn't be in that booklet, or where I can get them?[/postjack]

Not to ding GMC Paul, but those "Chevy Truck Wiring Diagram" booklets are a rippoff. Just an incomplete photocopy of the wiring schematics that are in the Chevy Truck Chassis Service Manual. I got one by mistake from Brothers -- instead of a '68 Owner's Manual-- but it got water-damaged before I could send it back. When I finally decided to use it, I was dissappointed to see the circuit paths were cut off. As a group, we need to let the vendors know they have a defective product.

[Rakort]

Originally Posted by '68OrangeSunshine

Not to ding GMC Paul, but those "Chevy Truck Wiring Diagram" booklets are a rippoff. Just an incomplete photocopy of the wiring schematics that are in the Chevy Truck Chassis Service Manual. I got one by mistake from Brothers -- instead of a '68 Owner's Manual-- but it got water-damaged before I could send it back. When I finally decided to use it, I was dissappointed to see the circuit paths were cut off. As a group, we need to let the vendors know they have a defective product.

Just an FYI. If your looking for a nice electrical schematic for our trucks I have one availble. Please see my signature. I have always disliked those schematics available in the manuals. Like you said they are somewhat diffcult to read.

[OhioDan]

Boydness- Ya might check out this website? Sure helped me out in the past.

http://www.geocities.com/chevroletc1070/wiringdias.html

Hope this helps?

[pjmoreland]

Do the following to check your brake lights:

1) Test for power on the orange wire that runs to the brake switch
2) With the brake pedal pushed, test for power on the white wire that runs to the brake switch (should be no power when pedal not pushed)
3) With turn signal off and pedal pushed, test for power on dark green wire and yellow wire running to "C" shaped connector coming from your steering column
4) With turn signal off and brake pedal pushed, unplug the round tail & stop lamp connector from your firewall and check for power on the contacts that correspond with the dark green and yellow wires.
5) Plug the round connector back in. Climb under the back of your truck and unplug the big round rear light harness connector on the crossmember and check for power on the dark green and yellow wires (turn signal off and brake pedal pushed,=). If you have power all the way to here, then there's something wrong with your lights themselves.

[Boydness]

Originally Posted by pjmoreland

Do the following to check your brake lights:

That's going to require help, so I guess I am going to have to wait until tomorrow.

I went through the testing of the firewall and rear pigtail connector when I was trying to get the rear lights to work. I made all the connectors on the mate for the rear pigtail's cables with slide splices, so that I could swap them around to troubleshoot.
I think that both the rear lights on the driverside might be going bad, there's playing the cables going into the base of the bulbs. If I tweak the cables, I can change the intensity of the brightness for the filaments.

I think that the issue could possibly be with the missing headlight dimmer switch? For one, if it is missing, how the F@$& are the headlights even working?
I remember that I had strange light problems when the dimmer switch on my Willys Jeep went bad. It took me awhile to figure out that it got some water in there at some point and that it was causing the sporadic problems.

What cables is the dimmer suppose to be connect to? I can not find it on the wiring diagrams.

Boyd

[pjmoreland]

Originally posted by Boydness:
High Beams: (Where's The Switch?)

The high beam switch should be located on the floor next to the kick panel underneath the air vent.

[Boydness]

Originally Posted by pjmoreland

The high beam switch should be located on the floor next to the kick panel underneath the air vent.

Great, easy enough, a floor dimmer.
Definately not installed there now...

The universal type are three prong. And I sure that Advance or AutoZone have a replacement.
What 3 colors do you have going to your dimmer? And can you tell where they are coming from/routed?

Because, I am guessing that I am going to have to figure out where they are currently and why they are not attached to the original dimmer.

I appreciate all the help that I get man.

Boyd

[Boydness]

Originally Posted by pjmoreland

The high beam switch should be located on the floor next to the kick panel underneath the air vent.

I went and got the floor mount dimmer switch. But was still unable to find any 3-prong adapter just hanging around off of the fuse block.
It is kind of hard to tell from the diagrams that I am using what is suppose to be running to it. I thought that I identified the dimmer switch, but was not sure. The 3 cables did indeed connect to what seemed to be the correct style of plug, although the connector was currently connected to a firewall mounted relay-type device.
The cables were light blue, light green, and tan(?), it also used the firewall as a ground apparently. (I highlighted what I thought reflected the dimmer switch/ mysterious device)

So, I disconnected the plug from the mystery devise and plugged it into the replacement dimmer switch from AdvanceAuto. And guess what?! It worked like it was designed.
Some joker must have installed a column switch relay type dimmer and mounted it to the firewall.

Anyone what to guess what the other problem with the rear lights was? My neighbor (that is building a '30s Ford hotrod) figured it out pretty quick. Something that I would not have guessed...


Boyd

[jhow66]

Your new bed was not grounded.

[Boydness]

Originally Posted by jhow66

Your new bed was not grounded.

The lights had poor grounds, yes.
The lights were also wired in reverse, the 2 cables (1 for each filament) for each set of lights were connected to the wrong signal. "Turn" was connected to the set for "Tail". (Neighbor mentioned that it may be the case).
And the brake switch was the wrong one, the plunger was too long, which would not have been a problem if the installed it to compensate, but they did not. The pedal would practically had to touch the floor to activate the brake lights. AND the joker even striped the plastic threads, so that it could not be adjusted/removed. I was eventually able to install the replacement one. Although, the return cable (non-power side) seems to have an issue past were it connects to the fuse block. I used a jumper to the firwall plug for the taillights to test that it was good.


Boyd

[pjmoreland]

Originally Posted by Boydness

Although, the return cable (non-power side) seems to have an issue past were it connects to the fuse block. I used a jumper to the firwall plug for the taillights to test that it was good.

Can you measure 12 volts on the orange wire that is connected to your brake light switch? If so, I suspect that you need to replace your turn signal mechanism inside your steering column in order to get your brake lights working.

[Boydness]

Originally Posted by pjmoreland

Can you measure 12 volts on the orange wire that is connected to your brake light switch?

Yes, the voltage is there.
How difficult is it to replace?
That may also explain why the right blinker position (up) for the switch does not want to lock unless the steering wheel is turned slightly clockwise. Or is that turn signal cam related?

Boyd

[pjmoreland]

Just a wild guess here, but maybe the stops are broken in the turnsignal mechanism, so the mechanism is traveling too far when you put the blinker on. When you turn the wheel, the cam may be pushing the turn signal mechanism back into position.

It's a bit of a pain to replace the turn signal mechanism. You will need a steering wheel puller to remove the steering wheel. You then remove the screw that holds the turn signal lever in place, and you remove the three screws that hold the turn signal mechanism in place. Depending on the year of your truck, you may have to remove the hazard light knob. You have to remove the bezel column gasket cover from the bottom of the dash. There is a thin metal cover on the bottom of the steering column that you have to tap down to expose the turn signal wires. It's somewhat of a challenge to get the turn signal pulled out of the column. You have to tilt up on the left side first and wiggle it until it comes out. Make sure you unplug the "C" shaped connector first.

If you purchase a replacement turn signal mechanism that has a straight connector on it instead of the "C" shaped connector, I'm pretty sure you don't need to purchase the adapter that is shown in the picture you posted. You should be able to reuse the "C" shaped connector from your old turn signal mechanism by popping the terminals out using a small straight-blade screwdriver.

[Boydness]

Well, I was going to remove the old steering wheel anyway...

If the brakes go through the turn signal mechanism then it is definately the culprit.

Sounds like a project for another day.

I need to sort out the wiper issue:
http://67-72chevytrucks.com/vboard/s...03#post1449103
Do you know how it is suppose to be wired? It's a '72 like yours...

[pjmoreland]

The brake light wiring does pass through the turn signal mechanism because the turn signals use the same filaments in the bulbs as the brake lights.