Intermittent Electrical Power Loss

[Millersir]

I have an electrical issue that I thought was a ground but now I have no idea. I replaced the battery, alternator, and fuse regulator and the truck was running great. I noticed that the eye terminal connector that grounded to the frame was broken. When I would pull that eye terminal away from the frame I would get no power. When I touched it to the frame I would get power.

So I went and purchased all new battery and ground cables. I've been testing the ground side connections by taking a multi-meter and measuring the voltage at the battery terminals (12.76v) then I take the negative on the multi-meter and see if I get the same reading at the engine block, the body, then the frame. I am getting 12.75v-12.76v all the way down to the frame. I cleaned the connections, I wire wheeled the grounding points. This thing is definitely ground...

I gave up last night because I was pulling my hair out after about hour 6 of this chase... I walked out to the garage this morning and boom... lights work, starts right up, no issues. Well then I walked in the house to take a phone call. When I came back out the damn thing is completely dead again. Its acting like the system isn't grounded. No lights, no brake lights, no turn signals, no horn, no start, nothing.

Could this be the starter relay not being ground to the body? Or perhaps the fuselink that comes off the starter relay? Any insight would be greatly appreciated. Thanks

 

[B RON CO]

Hi, as long as you are sure the negative goes directly to the engine block and body and chassis, I would look at the other wire that is on the solenoid post with the positive cable. This medium size wire goes into a harness to the alternator and regulator, so make sure it is in good shape. Good luck

 

[gr8scott]

Yup, could be the fusible link starting to go bad...

 

[Justafordguy]

Could also be where that wire connects together behind the amp meter. That bullet connector can get corroded and cause all kinds of odd problems.

 

[Rustytruck]

If you have a later model Bronco check the harness connection just before it goes into the firewall on the passengers side. Then check for power through the fuse box. then check the wiring connections at the dimmer switch. Goofy stuff happens at the dimmer switch.

 

[gr8scott]

Also, put some info about your bronco in your signature. At the top click Quick Links>Edit Signature.

 

[DirtDonk]

Definitely. Since Ford never put a ground on the frame, now's a good time to maybe even post up some pics of what has been done.
Is it stock wiring do you know? Aftermarket harness?

No one single ground should cut off power to the rest of the truck. If your frame ground (not stock) does it, then the main engine ground is not functioning properly either.
If they're both toast, then the one to the body is not functioning either.
Of course, if the engine ground was bad you would not get much in the way of cranking power at the starter either. And likely you would fry/melt any smaller gauge body ground that was trying to do the job of the much bigger engine ground.

But your test of attaching and removing some ground and having it consistently kill the power is an interesting find. And likely a key clue in this mystery.
Let's see whatcha got.

Paul

 

[Millersir]

You guys are awesome. I'm going to dig into some of these suggestions tomorrow and report back. Thank you!

 

[SHX669]

Both things that gr8scott said - fusible links are available at most parts stores and easy to replace . I had similar issues to yours on both current Broncos.
It's hard to help diagnose some issues without sufficient info especially electrical . Stock wiring , new harness, old fusebox , new box , wiring looks like used 4th of July sparkler's , new wiring and etc.

 

[Steve83]

I've been testing the ground side connections by taking a multi-meter and measuring the voltage at the battery terminals (12.76v) then I take the negative on the multi-meter and see if I get the same reading at the engine block, the body, then the frame.

That's exactly the correct procedure to check voltage through a wire under load (continuity). You just didn't finish... Stretch out your meter's probes, and keep checking EVERYTHING that needs to be grounded - just keep the positive probe on the battery (+) post as a reference. Try to check it WHILE the symptom is present. Once you have all the ground problems fixed, switch probes.

Put the negative probe on the (-) battery post, and work the positive probe along the positive (UNswitched, battery-power) wires. Any place you see the voltage drop (on either set of cables) is a problem.

No lights, no brake lights, no turn signals, no horn, no start, nothing.
Could this be the starter relay not being ground to the body?

No, that would only prevent the relay from engaging the starter.

Or perhaps the fuselink that comes off the starter relay?

Yes, remove & clean each ring terminal on the starter relay down to shiny metal so they all make good contact to each other. Click this & read the caption:


https://www.supermotors.net/registry/media/955475 (for phone apps)

Also, put some info about your bronco in your signature. At the top click Quick Links>Edit Signature.

%) x3 Look at Scott's, Rusty's, & DirtDonk's signatures for good examples. The more info we can see with each of your posts, the more likely we can help you figure it out.