Fuse Block Power

[Rcf]

I am working on an 83 Chevy K30.  The issue I need help with is getting power to the ignition switch.  The battery is connected to the starter.  From that same terminal two wires depart.  One to the terminal block on the firewall.  The other to the fuse block.  I got lights, but nothing that requires the ignition to be on or in ACC.  As I test I can get a circuit on those that do not require the ignition.  It seems the power is not making its way through the fuse block to the ignition switch circuit.

So, there are a couple questions.  From the firewall side, where is the input from the starter supposed to connect?  I am, certainly, not the first to work on this truck.  How can the wires be disconnected from the firewall side of the fuse block?

[MY1978]

I am sure you already did this, but did you check the "IGN" fuse?  Otherwise, I have no idea.  Someone on here with lots of knowledge will help.

[bd]

Will the starter crank using the ignition switch?  Give the red wires connected to the firewall junction block (located above the left rear corner of the engine) a firm tug.  Do any of the wires (fusible links) stretch or separate?

FYI - The B+ wires that feed the ignition switch bypass the fusebox and run directly to the ignition switch from the firewall bulkhead connector.

[Rcf]

Thank you, MY1978.  I will do that.

bd, No, the starter will not crank using the switch.  One of the red wires goes to the junction box on the firewall, but the only thing connected to the other side is a lead to the AC.  The firewall bulkhead connector is new to me.  Where would I find that?

[bd]

Are the fusible links intact and did you check them?

The firewall bulkhead connector is the ~3" square electrical plug located in the driver side firewall, directly behind the fusebox, through which wires pass between the engine compartment and cab interior.  It sounds like the wiring has been altered to some degree from its original configuration.  Refer often to the 1983 Wiring Manual to help sort out the details and discover deviations. 

The steering column mounted ignition switch or its connections may be faulty.  To diagnose, check for B+ on the two 12-gauge red wires that pass through the bulkhead connector between the engine compartment and the cab.  One of the red wires feeds power to the headlamp switch, the other feeds power to the ignition switch; both wires supply various fusebox circuits.  If you discover power on both sides of the bulkhead connector, check for B+ on the two "BAT" terminals protruding from the top of the ignition switch.  The ignition switch is best accessed by unbolting the steering column from under the dash and resting the steering wheel on the seat.  If you have power to the switch, but not through the switch, then the switch or its connections are faulty.

[Rcf]

bd:  I really appreciate your effort and advice.  Most likely the biggest problem here is that I am somewhere between a novice and below a novice.  I ask your indulgence.

Heading out to see what's what.  Apparently what I have been calling the "fuse block" is the "firewall bulkhead connector".  I really appreciate the link to the wiring manual.  Thanks. 

 I'm trying to sort through the manual.  I'll let you know what I find.

[Rcf]

bd:  Still no power to switch; but, thanks to you, I'm closer.  By the way, I haven't found any fusible link to check.

According to the diagram, the wire from the starter to the Firewall Bulkhead Connector attaches at the 2J position on the diagram.  On the inside the wire the position is 2 where the circuit splits into 3 Red 2G and 3 Red 2F.  3 Red 2G goes to the fuse block and connects at the T/L CTSY fuse.  I have power there.  3 Red 2F goes to the light switch.  I have lights.

I do need to check the IGN fuse, as MY1978 suggested.  There isn't any other way to get power to the switch that I can find.

[bd]

Two 12-ga red wires enter the bulkhead connector from the engine compartment.  You verified power on one of those wires.  What about the other?  Is it 'hot' where it enters the bulkhead connector from the engine compartment?

[Rcf]

Yes, both wires from the starter to the FBC are hot.  Several fuses have been hot, too.  Nothing additional with the key ON, though.

As far as an IGN fuse, MY1978, this truck does not have any.  There are several IGN plug ins but no fuse with them.

[bd]

So you've verified B+ on 2E & 2J (in the engine compartment) and 2G/2F (the headlamp switch feeds under the dash).  What about 2A (under the dash that feeds the ignition switch)?  If 2A is hot, drop the steering column and check for B+ reaching the two 'BAT' terminals on the ignition switch.  If 2A is dead, you will need to unplug the engine compartment harness from the bulkhead connector and inspect the condition of the Ckt 2E male and female terminals through the connector.

[Rcf]

Just to make certain, when you say "verified B+", you mean power? 

Never looked at 2A.  I sure hope it is the only red wire under the dash.

If I have to go as far as unplugging the harness from the connector, mine has a bolt in the middle that appears to secure the connector to the firewall.  With the bolt removed is it just unplugging it?

[bd]

B+ = battery positive or full battery power (generally 12.6 volts; 12 volts, nominal)

2A splices to several 12-ga red wires in the main cab harness up under the dash, just a few inches away from the fusebox.  The red wires supply B+ to the ignition switch and fusebox.  At this point, your focus should be on whether Ckt 2A exhibits constant battery power and whether that power reaches the ignition switch.

When you back out the center screw from the bulkhead connector the plug will be forced apart and separate from the firewall socket.  The bulkhead connector is filled with sticky black antioxidant that is reminiscent of cosmoline.  Don't be disturbed by this.  The antioxidant seals the connector against moisture intrusion, dust, and corrosive salts.  It's a good thing.  Just be warned that it is stubborn to wash off of skin and impossible to wash out of clothes.

[Rcf]

Thank you the advice about the sticky stuff.  Nasty for sure.

Anyway, I now have power to the switch, but - as you may imagine - there was enough juice to light dash lights, but not enough to crank.  Charging.  Will try in a little bit.

One thing I have noticed is that the bulkhead connector on my truck does not match the picture in the manual.  Manual pictures always seem to be pretty detailed and specific.  My connector has a bolt in the middle which is surrounded by wires.  None of the connectors for years around 1983 depicts what mine looks like.  Might not be a big thing, but makes me curious. 

If I haven't told you, thanks.  You've been a big help.

[bd]

One thing I noticed is that the bulkhead connector on my truck does not match the picture in the manual.  ...My connector has a bolt in the middle which is surrounded by wires.  None of the connectors for years around 1983 depicts what mine looks like.  Might not be a big thing, but makes me curious. 

Sometimes there are subtle variations in the wires that populate each cavity, but generally, the diagrams are accurate.  The bulkhead plug is actually an assembly of three discrete pieces.  The main harness passes through a siamesed pair that wraps on either side of the central retaining screw.  A third plug located along the left margin of the assembly transfers power to the rear lamp harness.

If your truck differs, post a pic.

[Rcf]

Having trouble posting pic.  Says it won't post jpeg file.