No instr panel, gauges, radio, ignition, start.

[one4fun]

86 K10, 350.

Had been driving my truck without any issues, parked in a parking lot for 5 minutes, started the truck up, pulled out of the parking lot, stepped on the gas, truck barely moved, like it was about to stall. Pulled it back into parking lot, turned off key, then turned it back on and nothing would happen, totally dead

No:
Seat belt buzzer,
Check engine light
gauges
radio
heater blower
ignition
Hazard lights

Not acting like a dead battery, just as if there is no power to the column. Head lights, high and low beam both work, dome light works. Checked battery connections and they are solid, battery is charged. Chassis grounds are good, starter wire connections are tight.

I'm thinking is either the ignition key switch or the electrical switch down at the bottom of the column, on the top side where you can't reach. But, the power door locks don't work now either, which I thought was odd since those don't need the key to work.

Suggestions on where to start troubleshooting?

Thanks.

 

[chengny]

Fusible links.

Start with the easy one - the one right below the junction block on the firewall.

Yeah, I just checked the schematics - that is a good place to look first. The power for the exterior lighting, courtesy lighting and horn doesn't pass through that one, so it would make sense that your headlights, tail lights, dome lights and horn would still be functional.

If you have no power coming into the junction block, you will have to check the fusible links that are just above the starter solenoid. There are two of them. One feeds the lighting circuit directly and the other feeds everything else (via the junction block, fusible link at the firewall, ignition switch and fuse block).

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[one4fun]

Can a fusible link be tested with a test light like any other wire?

 

[one4fun]

Also, my fusible link from the junction block goes from one wire to two wires,. Is there a replacement available for this? The ones I have seen are single wires.

 

[chengny]

Can a fusible link be tested with a test light like any other wire?

Yes. And a handy place to test that particular fusible link is at the alternator. Stay with me on this:

Your alternator should have a 2 wire plug-in connector - disregard that. It also will another (bigger) red wire that is secured to a stud with a nut. The stud/nut assembly will probably have a little protective boot covering it.

Next, as you note:

Also, my fusible link from the junction block goes from one wire to two wires,. Also, see the next post for more on this subject


The red wire that terminates at the stud connection on the alternator is one of those two you reference above (the ones that are spliced onto the load side of the fusible link that is connected to the JB). It is run straight from the split, around the back of the distributor, down the RH valve cover and terminates at the stud.

So to determine whether the link is intact - and capable of current flow - you can use your test light at the stud connection on the alternator.

Be sure to remove the nut and disco the big red wire from the stud before you test - just to avoid a false reading. The other red wire that connects with the plug is always hot and might cross-feed.

(Another option is to just pull the plug connector off the alternator - then you don't have to deal with getting the nut off the stud.)

Having said all that, the first place you should use your test light is on the line (inlet) side of the fusible link. That will tell you if the lower link (down by the solenoid) that feeds the junction block is good.

Put your probe on either one of the two junction block studs:

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If you get no voltage there, you can forget about checking the firewall link. No voltage at the JB means the primary link (one of the two down by the starter solenoid) is bad.

 

[chengny]

The fusible link is actually the short length of wire on the supply side of the plastic connector (the hard plastic cover with the amperage rating of the link embossed on it).

Here is a bit more detail on fusible links:

In addition to circuit breakers and fuses, some circuits use fusible links to protect the wiring. Like fuses, fusible links are "one-time" protection devices that will melt and create an open circuit.

Not all fusible link open circuits can be detected by observation. A blown link often, but not always, has "bubbly" appearing insulation making troubleshooting easier. Always inspect that there is battery voltage past the fusible link to verify continuity.

Fusible links are used instead of a fuse in wiring circuits that are not normally fused, such as the ignition circuit. For AWG sizes (wire gauges), each fusible link is four wire gauge sizes smaller than the wire it is designed to protect. For example: to protect a 10 gauge wire, use a 14 gauge link (or for metric, to protect a 5mm wire, use a 2mm link). Links are marked on the insulation with wire-gauge size because the heavy insulation makes the link appear to be a heavier gauge than it actually is. The same wire size fusible link must be used when replacing a blown fusible link.

Good and damaged fusible links:

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To replace a damaged fusible link, cut it off beyond the splice. Replace with a repair link. When connecting the repair link, strip the wire and use staking-type pliers to crimp the splice securely in two places.

Choose the shortest length that is available. A fusible link should NEVER be longer than nine inches. Fusible links longer than this will not provide sufficient overload protection.


To replace a damaged fusible link which feeds two harness wires, cut them both off beyond the splice. Use two repair links, one spliced to each wire harness.



Double wire feed fusible link repair:

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[one4fun]

Well, would ya look at that...

 

[one4fun]

Off to the parts store I go for 2 new fusible links.

Is a burnt link "normal" from age or do i need to do some searching for a cause of this?

 

[one4fun]

One more thing, the splice has 16 stamped on it. Napa has a 16 gauge, 8" fusible link available. Will this do the job?

http://m.napaonline.com/parts/PartsDetail.aspx?k=BEL784694_0452802200

 

[one4fun]

Update: New links installed and truck is rolling once again.

 

[chengny]

Oh boy! I wish you luck.

It may well be that the cause of failure was the link just got old and self-destructed, but my gut tells me otherwise.

From what I can see in the image, it certainly looks like that link failed due to an extreme over-current condition.

I wouldn't be surprised if it happens again. Many wiring faults are intermittent and get worse over time.

There is quite a bit of wiring on the downstream side of that link. If there is a break in the insulation anywhere in it - and it caused a short circuit to ground... it will come back to haunt you.

Might be a good idea to keep another link - and your crimping tool - in the glove box.

 

[one4fun]

Oh, I'll be picking up a couple more to keep handy until I can isolate the cause.