1970 Chevrolet C20 Pickup - Headlights and Backing up Lights not working

[ggalv]

Hi,

The headlights and backing up lights for a 1970 chevrolet C20 Pickup truck, 5.7 are not working. Appreciate your help in trying to figure out what is going on. I looked at the fuse box and really did not see a fuse for headlights and backing up lights.

Thanks

[Beecee336]

check that your connections are plugged in and tight to the box next to the fuse panel. mine was the same way.

[ggalv]

Attached is a picture of the fuse panel. Which connections should I confirmed that are plugged? Appreciate the help

[Dashman]

Check the fuse labeled "B/U LPS".

[RustyPile]

There is no fuse for the headlights. Headlights are protected by a built-in circuit breaker in the switch. The red power feed wire for the headlights is protected by a fusible link. You'll need to reference a wiring diagram for the following tests.

Using a test light or voltmeter, check for 12 volts on that red wire at the headlight switch..
If no voltage, check for a blown fusible link or broken wire on the main power distribution circuit. If you have voltage, turn on the headlight switch and check for voltage on the light blue wire. If no voltage, the headlight switch is bad..

If you have voltage, check on the light blue wire at the dimmer switch. If no voltage, there is an open in that wire between the dimmer switch and headlight switch. If you have voltage, check for voltage on the light green wire and tan wire at the dimmer switch. Voltage will alternate between these wires as you flip the dimmer switch.. If no voltage on either or doesn't alternate between the two, the dimmer switch is bad. If voltage is present on both, check for blown headlight bulbs or bad connections.

As for no backup lights. Check the fuse first. If it's good, with transmission in reverse, check for voltage at the backup light bulb sockets. The light green wire carries current for them. If voltage is present, check for burned out bulbs. If no voltage, Start moving forward with checking for voltage.. Many things can cause this problem. Loose or corroded connections, broken wires, bad or misadjusted backup light switch..

When an electrical gremlin rears its ugly head, it's next to impossible to point directly to the problem.. It goes unstated, you MUST have satisfactorily operating grounds....

[ggalv]

Thanks. I took out the fuse for the "B/U LPS", it has like a corrosion/red staining on one end, I am not sure if this right away means that it is not working? I am not seeing a break through the metal inside. I am not familiar with testing fuses, but going to be learning on this fuse.

The amps labeling its not very clear, but I think this fuse is 10 amps? Is this correct?

Thanks for the information regarding the headlights. Going to look into this, as I work on fixing this problem.

[Dashman]

The corrosion may or may not be affecting the electrical connection. Try to clean it with a cotton swap dipped in vinegar or 7-up, and maybe a brass wire brush. You could also place some dielectric grease on the metal of the fuse to help prevent any more corrosion. Yes, the B/U circuit fuse is 10 amps. Message RustyPile directly, I'm sure he'd be more than happy to help you personally.

One thing I always tell myself is, "I can't be the first one to have this issue", and sure enough 99% of the time it's true. Google "67-72" and whatever 2 or 3 other keywords is the key to finding these other posts where members here have solved their issues. It's a plethora of information such as wiring diagrams and other photos. The journey of solving issues is kind of fun. Good luck!

[Steeveedee]

Fuses can appear to be fine but still "popped". You can check yours by putting a test light on each side of the fuse with the key on. The truck does not have to be in reverse for this test.

[mr48chev]

Late to the party but this might help


The Backup lights aren't connected to the headlight circuit at all. Automatics have the switch on the column as part of the neutral safety switch and if it is broken the backup lights won't work. 4 speeds have the backup light switch on the transmisison. I'm at a loss at the moment to know where a column shift three speeds switch is.

Headlights check the fuse and at the fuse with your test light and then at the dimmer switch. If you have halogen lights the dimmer switches aren't great at handling the extra load or at least they aren't with the H-4 lights I have in mine.

[ggalv]

Thanks, appreciate your help and guidance. Going to use this information as I look into fixing this issue.

[dmack91]

Also, check the floor dimmer switch. I had one go out and cause problems with the headlights.