Fuseblock failure - What can go bad to cause it?

[mtnmankev]

I tested the underhood wires for power, the fusible links are good and power is getting to the firewall connector for the fuseblock.
But, most of the circuits at the fuseblock under the dash have no power.
What can go bad and where/how ?
I have a good harness to install (and I'm sure it'll be a bitch of a job) but I would like to know what to look for and where on the old one.

 

[C10MixMaster]

I tested the underhood wires for power, the fusible links are good and power is getting to the firewall connector for the fuseblock.
But, most of the circuits at the fuseblock under the dash have no power.
What can go bad and where/how ?
I have a good harness to install (and I'm sure it'll be a bitch of a job) but I would like to know what to look for and where on the old one.

are the dead circuits ignition and accessory? if so Maybe a ignition switch problem?

 

[mtnmankev]

Dead circuits are parking and tail llights, dash lights, cig lighter, dome/courtesy lights, and several terminals on the fuseblock where accessories can be fed power from.

 

[MikeB]

On my 82's factory harness, there were two large red wires (metric but approx 11 gauge) that ran from the BAT terminal on the starter. One went to the distribution block then on to the firewall connector, but the other went straight to the firewall connector. Can't remember how the fusible links were wired schematically, but there were two just off the starter and one below the distribution block. Also, it wouldn't be uncommon to have an intermittent terminal at the firewall connector.

 

[mtnmankev]

I need to separate the firewall connector from the fuse block, and verify that power is making it through the connector.
Then I can inspect the fuse block under the dash for anything that went awry.

 

[mtnmankev]

I remember when it failed, was at night and I saw a bright flash of light under the dash and heard a LOUD electrical "snap" then all went dark.
Turned around went back in the driveway and fired up the other truck to complete my mission.

Today, I finally finished playing musical wiring harnesses in the cab, took my time and inspected everything.
I even grabbed my blow gun nozzle and used compressed air to blow a 37 year collection of dust and crud out from under and in the dash.

The donor fuseblock and harness worked out perfectly, no shorts, taillights work again, (YAY !!!!!) and I now have more working spots on the fuseblock I can plug accessories into.
I will disassemble the old fuseblock at my leisure (and not during the heat of the day) for detailed inspection, but since the new one has everything working again, I sure won't trust that old fuseblock and harness.

 

[seniorbear69]

i had water leaking from the bulk head seam .straight into fuse bord. FANTASTIC !