Short in the headlight wiring?

[danisev]

I bought a test light and checked all the fuses with it. The light turns off when I pull the 40A headlamp fuse and stays on for the rest of the fuses.

Need all the help I can get!

Dan

 

[franklin2]

I assume you had the testlight in series with the battery? Did you have one of the doors open when you were doing your check and pulling the fuses? The domelight will foul your test.

 

[danisev]

I disconnected the negative battery terminal and clipped the wire from the test light to the battery connector wire.

Then, I touched the point of the tool to the negative post of the battery.

The light came on. I am pretty sure I had the door closed while checking it, but I am going to try again. I did not know that was important.

The reason I am doing this is because the car quit on me the other day and would crank but not start. Next day the battery was completely drained.

I recharged the battery and it started up again, but when I went to buy beer, the car would not start again in the parking lot.

I disconnected the battery, and drank a beer and then was able to start it and drove home.

Sounds like a short circuit, right?

 

[RonD]

Good page to Bookmark for Bronco II info: https://www.broncocorral.com/tech_library/

If you scroll down to Electrical, and then select Wiring Diagrams
Then scroll down and select 1989 Body PDF you will get this: https://www.broncocorral.com/library/diagrams/89_b2_body.pdf

Looks more complicated than it is, lol

In the upper left you can see the Main Light switch that is powered by Fuse #2 40amp in engine fuse box
You said that when you remove Fuse 2 power was no longer flowing thru the Test Light
So next step would be to pull out the main light switch and unplug its connector
Then repeat the Test
If test light stays off with fuse 2 in place then the wire to the Main Light switch is OK
Than means Main light switch is most likely bad, it is powering something in its OFF position which is draining the battery

You can leave battery connected and put test light in place of a fuse, that will also tell you if power is passing thru that one fuse, test light on or glows

On all computer controlled engine systems the computer does draw power when key is off, not much, 0.02A(200ma)
Also Radio's draw power key off, for holding Clock time and Radio pre-sets, 0.01A(100ma)

 

[dvdswan]

Welcome to the site.

 

[danisev]

I pulled the switch in the picture believe this is the main light switch RonD had told me to check.

I can’t figure out how to attach a video, but after pulling the switch and 40A fuse, the test light blinks on and off like a hazard light.

Any idea what that means? In the meantime, I am going to recheck the fuses under the steering wheel with the door closed.

Also, if there is a way to attach a video, I can show you the blinking test light.

I am going to check again, but I don’t think it blinks if the main light switch is connected, just off.

 

[Curious Hound]

I pulled the switch in the picture believe this is the main light switch RonD had told me to check.

I can’t figure out how to attach a video, but after pulling the switch and 40A fuse, the test light blinks on and off like a hazard light.

Any idea what that means? In the meantime, I am going to recheck the fuses under the steering wheel with the door closed.

Also, if there is a way to attach a video, I can show you the blinking test light.

I am going to check again, but I don’t think it blinks if the main light switch is connected, just off.

We don't host videos on-site. Upload it to YouTube and put the link in a post here.

The blinking can only come from the turn signals circuit or the hazard flasher circuit. Make sure you didn't bump one of those switches to the "on" position.

 

[danisev]

I think you are right about the hazard lights.

This morning I went to do the test again, and the light did not turn on!

However, I drove around the park and afterwards, the truck failed the test light check again, and again the same circuit.

I could try to replace the whole harness, but if I can find the exact problem, the repair would be a lot cheaper.

Also, as far as I can tell, there is more than one harness involved in the circuit; in the engine bay and under the dash, so that could be hit or miss.

I am looking for information on how to use the test light or a multimeter or even just common sense, so that I can find the problem (short) wires and replace them.

The Bronco Graveyard has an aftermarket headlight harness for sale, and they are relatively cheap, so I could try my luck at fixing the problem by replacing mine.

However, I do not know exactly where the wires short and it could be on a different harness.

I am going to check the fuses under the dash again with the door closed, maybe I can narrow it down.

 

[Curious Hound]

Don't know if this would be helpful to you. If I get some free time this evening, I'll try to read through your thread again and see if I can give some more specific advice.

 

[danisev]

Now it will not start. I am going to recheck the fuses and possibly order a new headlight harness and dashboard harness.

I am going to look around for information on how to uninstall the harnesses, and any help would be great.

There is a video on YouTube, but the guy’s truck is already completely taken apart, so I do not think that would be much help.

Ideally, somebody would walk me through this.

My friend whom I had mentioned earlier may help, too.

 

[Curious Hound]

You might do better getting a multimeter instead of wiring harnesses you probably don't need. You are going to need specific readings for this instead of just using a test light.

If it won't start, we need to know the condition of your battery.

So, to review, tell us if this is correct.

1. Original problem, I assume, is something was discharging your battery and you think it is in the headlight circuit?

2. New problem. Truck won't start. Does that mean starter does not engage to rotate the engine? Or starter works but engine won't fire?

 

[danisev]

Hello,

As a follow up my problem was fixed.

I had a friend come over who is better with auto tech than me and we figured out the fuel pump was not working by ear, and I believe we had the engine start with starting fluid.

So we took a look inside the fuel tank and a ground wire was loose.

When reconnected, the truck started and ran again.

Unfortunately, low oil pressure has made it necessary to rebuild the engine, which is a project that I will start when I have my garage cleaned up.

Dan

 

[Curious Hound]

which is a project that I will start when I have my garage cleaned up.

I’m glad that’s not a prerequisite for my projects.