No electrical power

[Mike Bryan]

Ok, get this, I have a 76, it is a get in and start and go anywhere bronco. Today, I was installing a new fuel and volt gauge in my dash mounted pod. I have had this setup for 20 years. I disconnected the battery, and installed them. Went to start and put it back in garage, nothing, I have 12.8 volts at battery and solenoid, but absolutely nothing works, except for voltmeter. All fuses are good, it is the factory harness. Not quite what to make of it. Any ideas? Thanks, Mike.

 

[DirtDonk]

There are only two (well, three actually) places that can kill power to the whole truck.

Since you were messing about under the dash I would look at the Black w/yellow wire adjacent to the ammeter in the stock cluster. If the big push-together connector has come undone, or has broken somehow, that will kill all electric power.

The other two are the battery cables. Since you said you have power to the starter relay your positive cable is likely ok. It can still be defective and show voltage there and not crank the starter, but unlikely to show voltage on the meter and not to be able to at least turn on a light somewhere.

The negative battery cable could do it as well.
And main cables do go bad. It does not happen very often where you can't see that the outside is buggered, but it does happen. Has happened to me once, and to several other members here over the years.

So check those things and see what you find.

Paul

 

[DirtDonk]

Today, I was installing a new fuel and volt gauge in my dash mounted pod.

Just out of curiosity, did you mess with the original fuel gauge wires to run to the new gauge? If so, that might be when something happened to the Black w/yellow wire.
In case you didn't know already, that large (roughly 10ga) wire is the heart of the electrical system for your Bronco. Feeds the fuse panel, the headlight switch and ignition switch directly, and everything else indirectly through the ignition switch.
It is also the main "loop" that runs from the alternator to the battery to keep the battery charged.

Speaking of which, if you messed with the starter relay/solenoid at all while you were disconnecting the battery, if you did not put that Black w/red (or all Black) wire back on the same post as the battery cable, that would also explain your no-power situation.

...but absolutely nothing works, except for voltmeter.

Out of curiosity, where is your volt-meter connected? And is it in the dash in place of the old ammeter, or is it under the dash in the same pod as the other new gauges?

All fuses are good, it is the factory harness.

Another FYI the main power feeds the fuse panel, but does not actually pass through it with a fuse. So even though it's always good to check fuses, there is nothing in the fuse panel that can kill the power to all accessories.
Some fuses are hot all the time (hazard flashers for instance) and others are hot only with the key in the ON or ACC positions (like the heater and radio). There is one fuse (I think it's that impossibly small one!) that is only hot when the headlight switch is on and the dash light rheostat is turned on. It's the fuse for the dash lights in the cluster and the light bars next to the control knobs, so it's good to remember the headlight switch. Many an EB owner has been stymied trying to find power to that fuse connection when the headlight switch is off!

Good luck!

Paul

 

[AC932]

Not a terrible idea to check corrosion on your battery and solenoid posts as well. I had a bad connection to the solenoid (and a partially dead solenoid itself) that would randomly kill all power until you disconnected and reconnected it.

 

[Mike Bryan]

Thanks for these quick replies, I did disconnect the fuel gauge wire to the stock gauge cluster, I may have inadvertently disconnected the wire in question. I will check it out as soon as my back says it’s ok to torture it again. Thanks again!

 

[B RON CO]

Hi, does anything else work like key off things including headlights or horn?
How about key on things like blower motor and directionals?
If the small wire at the solenoid, under the cable from the battery is off, it won't crank the starter.
Good luck

 

[DirtDonk]

...I will check it out as soon as my back says it’s ok to torture it again. Thanks again!

I hear that!
One way to get around that, should your back decide not to cooperate in an acceptable timeframe, removing the driver's side air vent should not require too much articulation on the part of your spine, and the remaining hole in the cowl lets you look right down on the back of your instrument cluster.

Worth keeping in mind anyway.

Paul

 

[Mike Bryan]

Yellow and black wire was ok, I have no power to anything under dash, nor to fuses.There is no corrosion on anything. But, my new volt gauge is showing 12.7 volts. So weird. Checked all my grounds, seems good.

 

[B RON CO]

Hi, are you using s test light to check for current?
The test light shows nothing at the ignition switch, and nothing at any post in the fuse box?
Good luck

 

[Mike Bryan]

Yes, a test light, I like the idea of looking thru the air vent, I am done for the night. In 25 years with this thing, never had an electrical problem. Thanks for everyone’s help. Will update tomorrow.

 

[chuckji]

How about the fusible link? If there is no voltage on that Black/Yellow wire Paul was talking about, the fusible link might be burnt. Circuit 38A on this diagram.

 

[Mike Bryan]

Thanks, will check fusible link in morning. Will update.

 

[AC932]

If ya don't find anything wrong with that fuse link, then I'd say its probably time to start cutting down the circuit.

Seems to me a good starting point for that would be to go from battery positive directly to your starter. Make sure you're in park or neutral (and try not to touch anything metal with your skin) and just touch the battery positive cable and the starter cable together real quick. If it sparks and makes some noise, then great, your battery cables are good and can carry current! Your issue is elsewhere.

If not, try quickly tapping the positive cable to the negative terminal. If no sparks, then your positive cable is bad, or something really funky is going on with that battery of yours.

If that sparks, then you have current through the positive cable. That means that either the starter wasn't grounded, or the battery wasn't. Disconnect your battery ground cable from the block and tap it to the end of your battery positive cable. If that sparks, then all your cables are good, and either the ground to the block or starter were bad. If no sparks, your battery negative cable is shot.

Remember, a test light is (generally) really low current, so just cuz it can light up don't mean your cables can carry what you need them to!

Good Luck, and don't hurt yourself!

 

[Seventee]

Twice I've run into the same issue and both times it was the plug that passes through the firewall from the engine side, near the back of the driver's side valve cover. Both times I cleaned the contacts and viola! power again.

 

[jedblake]

Fuse link was my issue. Are you seeing voltage at the coil post with the key in the on position?

 

[Mike Bryan]

It’s fixed!

First of all, let me say thanks to everyone’s help and replies, I checked all suggestions, and it allowed me to straighten up some messes in the wiring department. My problem stemmed from me changing out the ammeter gauge to a voltmeter. I failed to mention that in my original post, sorry bout that. So, the wiring on a ammeter is different than that of a voltmeter. The two wire marked positive and negative on the ammeter go to their respective poles on the amp gauge. On the voltmeter, those two wires go together. Voila, I have power. Lesson learned. All is good in Bronco land. My gauge pod sits atop the dash with oil pressure, water temp, fuel level, and volts. All Autometer Sport Comps. The gauge pod is made from aluminum, and I mounted it atop an aluminum plate. All made from recycled yield signs. My original instrument cluster is still in, just the turn signal lights are used. My speedo went out years ago, I now use a Garmin GPS for all data. Thanks again, this forum is the best.

 

[DirtDonk]

Yellow and black wire was ok.

Hey, nice to have power back!
But, uh... Well, what happened with that first test a few days ago? You said the Black w/yellow was "ok" when it really wasn't. Were you looking under the dash, or somewhere else? For future reference to help others, where were you looking when you thought it was good, and what did you see?
You say that when you re-connected the two halves it all worked. Glad you did find that break and it was indeed the hoped-for simple fix.
As you found, that's the key wire for literally the entire truck.

...So, the wiring on a ammeter is different than that of a voltmeter. The two wire marked positive and negative on the ammeter go to their respective poles on the amp gauge.
On the voltmeter, those two wires go together. Voila, I have power.

Kind of got me confused again with the wording. Correct in that the voltmeter is wired different from the ammeter, but the ammeter does not have the posts. It has an inductive loop that the wire passes through. A very safe design in fact, and better than 90% of the other ammeters out there from that era.
Are you simply transposing those two gauges in your description? It's the ammeter that puts those two halves together, and does not have any posts. The voltmeter on the other hand does have a positive and negative post.

Not bustin' yer chops. Just trying to make sure everything is edited for accuracy. Or find out if you had some unusual setup in your rig.
You know.... For future generations and all that!;D

Paul

 

[Mike Bryan]

Yes, my Summit amp gauge has two posts, marked +,-, my new Autometer gauge had a + post and a ground post also. The ground on the new autometer gauge goes to chassis ground, and the two wires, red and black together on th positive post.