Bronco won’t start- need your help!

[White Knight]

4XFUN..... battery checked out ... to be sure, I took a battery from my son's car that is new and still nothing

 

[Oldtimer]

There are two plug in connectors on the alternator and one small post which has a black with yellow stipe wire connected to the post. that black and yellow wire is part of a harness from the dash and has been that way for the 23 years I have owned it... circled in picture the harness that comes from dash that the black with yellow stripe wire is part of that end up connecting to a small (only) post on the alternator

BINGO

The black/yellow 10GA wire on alternator,
takes charging current from alternator,
to dash where it,
has splice connections to ignition switch and headlight switch,
then thru ammeter loop and ends at a bullet connector.
The bullet connector is connected to black 10GA wire that runs out to battery post on starter relay.
If black wire is compromised, or bullet connector is in poor condition, 12 volts cannot get from battery back to ignition switch, and nothing works.

PO installed an alternator with internal regulator. These typically put out more then original 38 amp alternator and will overload 10GA wire in harness. You've been lucky for 23 years.

Minimum repair:
Replace black wire, add a fusible link at starter relay battery post, AND verify condition of bullet connector behind instrument cluster.
You can see it if you are flexible enough to get on floor amd look up at dash.
Easier acces is to remove fresh air vent from cowl and look at back of cluster.

 

[White Knight]

How long should the fuseable length be to be effective?

 

[Oldtimer]

The effectiveness is based on the gage, not the length.
A couple of inches should do.
You do not want to bundle them in a harness.
Theye are designed to burn out and protect the rest of the wire run, and you dont want it bundle against other wires when it burns.

Fusible Link Kits - CE Auto Electric Supply - Automotive Electrical Solutions

Fusible Links are used to protect runs of wiring. They are also commonly used by the OEM on the alternator charge lead. We do not recommend the use of fusible links inside of the vehicle due to the nature of how they fail as this can be a fire hazard. Fusible Links are sized 4 wire sizes up from...

ceautoelectricsupply.com

 

[Oldtimer]

that large gauge wire is a 4 gauge wire on a fuseable line to my stereo amp

What size fuse for your stereo amplifier circuit?
The reason I ask is 4GA wire, with minimal voltge drop for amplifier, would indicate a 100 amp circuit?
If the amp needs that much current and the alternator is capable of supplying it, all that current will try to flow thru the 10GA stock harness.
You may want to upgrade the alternator harness and direct wire to the battery.

 

[White Knight]

got the 10 gauge wire spliced in the 2 wires (yellow & black) then have the other end spliced in 14 gsuge fuseable wire connecting it to the solenoid. Car started up, ran long enough to pull it out of the garage then died and back to nothing...not a click. Checked all the wires ...all are in tack.

 

[White Knight]

got the 10 gauge wire spliced in the 2 wires (yellow & black) then have the other end spliced in 14 gsuge fuseable wire connecting it to the solenoid. Car started up, ran long enough to pull it out of the garage then died and back to nothing...not a click. Checked all the wires ...all are in tack.

As far as the amp..... it has been running this way for 5 years .... no problems

 

[Oldtimer]

Check the fusible link for continuity.

 

[White Knight]

with a test light ----i should have it clipped to neg on battery and when touching fusible link with probe it should light up showing power flowing through it.....correct?

 

[Oldtimer]

Yes

 

[White Knight]

Yes

So I did that … checked at splice of the 10 gauge and the fusible link and it lighting it up

 

[Oldtimer]

Check the black/yellow wire where it is connected to small post on back of alternator.

 

[White Knight]

checked black and yellow on alternator and it is lighting up

 

[Oldtimer]

That means you have power from battery to dash, and back out to alternator.
Do headlights work?
Do accessories (amp, radio, turn signal, etc.) turn on when key is in accessories position?

 

[White Knight]

No— frustrating. Started right up, sat for awhile at idle then just stopped.

 

[Oldtimer]

Check black/yellow wire at alternator post, with headlight switch in off AND on positions.
You may have a poor connection that will show power, until load is applied.

 

[ba123]

GREAT news that you got it started, nice help from @Oldtimer

It's a bad connection somewhere or a something shorting out.

 

[White Knight]

I can’t figure it out- I have checked every wire involved ….it started up tan high for about 30 seconds then settled into good idle . Then just died…… now back to nothing…… no lights, turn signals, radio

 

[ba123]

Check that wire going to the ignition switch again.

I would bet that somewhere after that bullet connector, you have a short.

 

[dmoses42]

Bad ignition switch?