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Old 03-04-2018, 09:39 PM   #1
85raiderburban
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short circuit fuse problem

driving down the freeway, she lost all power (no head/tailights, no instrument/gauges power, no cd deck). There is no switch 12v power either. turn key to acc position and it acts as if battery cables are disconnected.
only the aftermarket cig lighter used for usb adapter has power (since its hooked to constant 12v).The radio and gauges/instrument fuses were blown. BUT the yellow wire (pictured) I had from the orange (ign switch 12v) going to the engine side of the firewall powering a seconary junction block specifcally for inline electric fuel pump, 4L80 +12v, LED fog lamps and trans cooler fan.
For some reason the fuse didnt pop but instead when all this occured but MELTED. Has anyone had this happen before??? And why do i have no power? the starter wire is tight. if i have to i will remove and rewire fuse box and external plug to get this back up and running
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Old 03-05-2018, 01:36 AM   #2
kwmech
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Re: short circuit fuse problem

I've seen the cheap knock off chinese fuses do that.
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Old 03-13-2018, 04:17 AM   #3
85raiderburban
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Re: short circuit fuse problem

UPDATE: never found out what was the short, but instead re routed my starter wires, and all +12v connections from bat post to junction block and alternator. headlights, tailights, gauges and back lighting all work now. I have switched key on power but no starter crank. ????
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Old 03-13-2018, 10:59 PM   #4
Irish1941
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Re: short circuit fuse problem

No start..check fusible link on purple ignition wire. Start circuit is dead if nothing in START position.

Hard to tell electrical troubles without seeing them BUT I'd
say no short there...resistance melted that fuse THEN system ground out killing the dash etc. Hot lead to grounds cause shorts
Pretty sure I figured out what happened.
Corrosion in the fuse holder caused heat build up. Fuse melt down which caused chain reaction in other tied in circuits.
However you need to fix that wiring. That is fire dept worthy right there. 30 amp fuse on 14g wire with 70 amps of draw is asking for trouble.
I would go at least a 10-12g wire under 8' long with what you said was on there.
Fuse for the wire size NOT the load. Fuse protects circuit NOT the accessory.
If load is too much for the wire then split the circuit.
Let me know if you need help in wire vs fuse circuits.
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Old 03-14-2018, 07:29 PM   #5
85raiderburban
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Re: short circuit fuse problem

Quote:
Originally Posted by Irish1941 View Post
No start..check fusible link on purple ignition wire. Start circuit is dead if nothing in START position.

Hard to tell electrical troubles without seeing them BUT I'd
say no short there...resistance melted that fuse THEN system ground out killing the dash etc. Hot lead to grounds cause shorts
Pretty sure I figured out what happened.
Corrosion in the fuse holder caused heat build up. Fuse melt down which caused chain reaction in other tied in circuits.
However you need to fix that wiring. That is fire dept worthy right there. 30 amp fuse on 14g wire with 70 amps of draw is asking for trouble.
I would go at least a 10-12g wire under 8' long with what you said was on there.
Fuse for the wire size NOT the load. Fuse protects circuit NOT the accessory.
If load is too much for the wire then split the circuit.
Let me know if you need help in wire vs fuse circuits.
there is no fusible link at the starter wires. I replaced them with 12 gauge wire at the BAT+ terminal. i pulled apart the fuse panel and firewall plug. cleaned all the connections. It did have some the anti corrosive adhesive in there but not much. that yellow wire with melted fuse has been replaced with 12 gauge wire now. do you have a diagram of the starter circuit or if its snaked in wire I'm looking for?? I appreciate the feedback!
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Old 03-14-2018, 11:16 PM   #6
Irish1941
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Re: short circuit fuse problem

Should have a purple wire and thicker red wire with fusible link on it at the starter.
Purple is ignition to solenoid. Its hot only in start position.
Comes off firewall and drops down at rear of passenger side of the block
Red is to junction block which feeds entire truck.
The red one you replaced needs some kind of protection on it due to 12v constant and if battery or alternator has melt down, there is nothing to stop voltage from rest of the wiring.
Where is your alternator charge wire going to? Straight to battery?

Check the ignition switch connection under the dash.
Check the neutral safety switch.
If it checks good, go to the purple wire on solenoid.
Use test light to check for voltage when key is turned to start.
No power there, trace it back look for breaks or melted wiring.
If you do get voltage on start position, then test the starter solenoid.

Here's a diagram.
http://www.73-87chevytrucks.com/tech..._V8_engine.jpg
let me know how you make out.
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