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Discussion Starter #1
Hi everyone. I'm very new to Broncos (bought my first earlier today, 1987 XLT w/ a Mustang 5.0 HO engine). Anyway, it started and drove just fine, but when I flicked on the AC and put the fan on full, the car just shut down instantly. Now, the radio, windows, climate control, etc, have no power. The car won't crank, and I don't hear any fuel pump priming noises. The headlights, central locks, and the ignition dinger (annoying thing) continue to function as intended. Does anyone have a clue where I could start looking for this electrical problem. The fuses looked ok, but it was cold and dark outside, so I towed it and decided to diagnose tomorrow. Any suggestions are appreciated, and I can give you whatever other information you would like (when I check the car out tomorrow).

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Eamon
 

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Discussion Starter #3
Check fuses in the daylight.
All the fuses have been confirmed good.

I checked the ignition switch (replace with a new one) and it didn't fix it. So, I tested the two large yellow leads on the ignition wiring harness and got 6 volts each. I take this to mean that I have some dead fusible links somewhere.

I found the power distribution block near the batter and I see two large yellow leads (same gauge as the ignition yellow leads) with fusible links. Do those go to the ignition switch?

If not, where should I look for more fusible links on the ignition leads. Also, if anyone can point me to wiring diagrams more comprehensive than those on Autozone's site, I'd appreciate it.

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Eamon
 

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What you describe is exactly what my truck did when the voltage regulator went out. Driving around was fine, but once accessories got turned on the truck would cut out since the battery wasn't getting charged.

I'd start by checking battery voltage, and then check connections at the battery, ground at the engine block, and all of the connections on the starter relay. These are all free checks and are typical of what you describe.

Justin
 

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Discussion Starter #5
Well this problem has finally been solved. The wire that runs from the battery to the firewall (12v lead for the ECU and the ignition switch) is spliced in the large bundle of wire that runs along the driver side fender wall. It tore it apart and found that the solder that Ford used had corroded, leaving me with a terrible connection. There was too much resistance across it for me to get 12v. I cut out the bad wire and put in a new length. Viola.

Eamon
 
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