fuse panel detailed description or diagram

[dmjlambert]

I have searched but not found this. Has anybody made a picture or diagram of the fuse panel for 67-72 that describes in detail what each fuse is for and whether it is always hot or switched at the ignition, and what the terminals are for and whether they are always hot or switched? I can't really make sense of most the labels that are printed on the fuse panel, and if I manage to figure one out, I can't retain that in my memory for the next time a few weeks or months later, when I go try to figure the next thing out. So, looking for some sort of detailed reference guide. There are some I understand such as IGN UNFUSED.

[VetteVet]

I think it would be better to trace the wiring harness from the battery positive post to the fuse box for a better understanding of how the system works.

Positive current electricity begins at the battery Plus post with the large cable to the starter solenoid. In addition there is a fusible link from there to a junction on the right fender to protect the key off electrical circuit.

From the junction a 12 gauge red wire continues across the top of the radiator and down below the left headlight to the main junction of the positive power wires.

Shown below are the points I have mentioned. The main junction includes wires from the battery, the alternator, the regulator, and the main cab feed wire to the firewall junction block.











This is the firewall junction block showing the 12 gauge red power wire for the cab. Notice the large purple wire for the starter solenoid and the cloth covered wire which is the resistance wire for the ignition coil.



The green and blue wires are the temperature sender and the oil sender wires respectively.

Next we get into the cab and follow the large red wire up the left side of the diagram. Notice it joins three other wires which are the power feeds for the horn relay the, the ignition switch, the headlight switch and the fuse panel.
All these are full time key off power wires.




Remember the large red wire is key off power to the fuse panel and it powers the things which do not require the key to be on to operate.
The stop lights
The hazard light flasher
The dome light
The parking lights.
The cigar lighter terminal.
The backup lights fuse.
The radio terminal.
Here's a view of the wiring for the fuse panel. It's the same one shown above.



Notice the large red wire from the junction.

The main attachment point feeds the fuses for the items mentioned just above which do not require key on power. The primary output wire for these items is the orange wire, which feeds the stop/taillight fuse, the dome light fuse, and the headlight switch, for the parking and dash cluster lights.

The dash cluster lights are fed from the headlight switch through the variable resistor in the headlight switch, back to the fuse panel via a green wire, to the Pnl Lts fuse.

I think that's all for the key off fuses.


Looking at the diagram for the key and headlight switches we see a 12 gauge brown wire and a 12 gauge pink wire on the key switch. The brown wire is the accessory wire and it goes to the fuse panel to feed the wiper fuse, the turn signal flasher, and the heater, AC fuse.
(NOTE)- 1967 trucks did not have an accessory key switch and no brown wire.

The pink wire from the key switch goes to the junction In the denter of the diagram and tees off for the fuse panel and the ignition coil + terminal.
The pink wire at the fuse pane feeds the IGN Unfused terminals and the cluster feed fuse.

Here is a diagram of the key switch and the headlight switch.





And here is a fuse panel with the fuses and terminals labeled. They can vary
slightly.



I'm sure I've missed something so if you have any questions let me know.

[dmjlambert]

Thanks, great info. I'm going to read the heck out of this and study.

[68c10airstream]

DMJLAMBERT, you are in the best of hands with VETTEVET, patient, tons of info, kinda like one stop shopping for free!! Enjoy

[dmjlambert]

OK, so I searched and figured out nobody has done this before, perhaps nobody was interested other than me. I guess I'm a visual person. I mapped it out.

Switched and dimmed for dash lights means this section has 0 to full current depending on the headlight switch and dimmer position.

Return from fuel level sensor means this is attached to the ground side of the fuel gauge, and the wire that plugs into it supplies ground through the float's variable resistor. This doesn't really belong on a fuse panel, as it is only a connector and has nothing to do with supplying power to anything, but perhaps it was considered convenient.

Always On means this always has battery voltage regardless of position of ignition switch.

Accessory means this has battery voltage in accessory and on positions of ignition switch.

Key On means this has battery voltage in on position of ignition switch, but not in accessory position.

[lsversaw]

Thanks for your effort, dmjlambert. The fuse panel labels have always been cryptic to me, too. Now it's clear to me that each of the 4 powered section has at least one open terminal for add-ons. Nice.

[Andy4639]

I added this fuse block into my 71.
It sits to the right of the column. It gives me plenty of fusible space for extra's. I tied it into the fused connection on the main block.

[Hightower79]

Apologies for resurrecting an old thread.

What does the CLSTR fuse operate?

[dmjlambert]

top right fuse is cluster illumination, one below it is fuel and temperature gauges and warning lights

[Hightower79]

Originally Posted by dmjlambert

top right fuse is cluster illumination, one below it is fuel and temperature gauges and warning lights

Thanks!! That's brilliant! Just need to get rid of that silver foil around the fuse now

[Rdwagoner]

The 18g black wire in the first picture that runs the firewall into the junction block. Is it needed? I don’t think I have it.

[dmjlambert]

The 18B wire and the 18B/W wire with fuse holders in them are for the ammeter gauge, if you have an instrument cluster with gauges.

[Rdwagoner]

Thank you, I have the factory cluster but will probably have to use some aftermarket gauges. I’m on the final stretch of the build but I’m having issues with the electrical portion. One headlight dim, only left blinker works, wipers work on occasion. Any options besides a $500 painless harness? Upgrade fuse block? Thanks

[dmjlambert]

It depends on your goal. If the insulation on the wires is not cracking or melted and wires are not corroded, you can just troubleshoot problems one at a time until resolved. Post new questions as you think of them in the Electrical section and somebody who knows about that particular topic will help. Pictures are useful.

In my case the wiring appeared to be in good condition but I had a dozen wires in various locations eaten by rats, and I had 1 melted connector for the heater fan switch. I soldered in sections of new wire and used heat shrink tubing to fix the wires, and put a new-to-me used connector on, and it was back to 100%.

Most of the switches and bulbs were bad in my truck, that would not have been fixed by a wiring harness. I just tested and replaced all the bad lights, such as the headlights and turn signal lights. And replaced the various switches, such as headlight, hi-lo dimmer, and turn signal switch. Some people just replace all the wiring because they are doing a complete restore, and replacing everything else so might as well replace the wiring.

[dmjlambert]

There are 2 types of factory instrument clusters. Some trucks have a cluster with speedometer, fuel, temperature, oil pressure, and ammeter gauges, and other trucks have a cluster with speedometer and fuel gauges and the rest of the indicators are warning lights. It is possible to change from one instrument cluster type to the other, but some truck wiring and the pinout of the cluster connector would need to be updated. If you become a premium member here on the forum you can post want-to-buy ads in the parts section. I have done that for several items, including an instrument cluster and some electrical connectors that another forum member cut out of his old stock wiring harness for me.

[Rdwagoner]

Thank you for the reply! I’ll just have to troubleshoot each one and possibly replace things as needed. I’ll post further electrical issues in that section. I have the second type of cluster. Speedo, fuel and warning lights. Not much works on it after my swap.

[jdry87]

The 18B fuse wire for the ammeter may run down the inner driverside front fender instead of the firewall to passenger. Then it goes across the front a top of the radiator to the battery. It does on my 1970 k2500. I traced it down, cleaned the inline fuse (full of corrosion) and now my ammeter works.

[Unofornaio]

exactly the waters Im heading into now..THANK ALL OF YOU FOR THIS THREAD..

[koolkat]

Originally Posted by Andy4639

I added this fuse block into my 71.
It sits to the right of the column. It gives me plenty of fusible space for extra's. I tied it into the fused connection on the main block.

Where did you tie this into the OEM fuse block? Did you add a relay inline? Any pics? Is it still working for you, any problems? Thanks

[Andy4639]

I have the one under the dash and one on the drivers side behind the seat for the heated seats & radio amps. Both are working fine with no problems.

[jwilson7981]

Do you know where I can buy a new firewall junction box. Mine is burned up

[Rookiebuilder]

Where specifically does the br/blwire from the cluster gauges go? What is meant by “terminal by battery”? I’m trying to finishing wiring my 67 and get it going but I’m lost where this brown/black wire goes from the instrument panel cluster? Do I even need it?

I installed a 5.7 TBI woh a 4L80e tranny in my 67. Any help would be great. Thanks
Posted via Mobile Device

[pjmoreland]

Originally Posted by Rookiebuilder

Where specifically does the br/blwire from the cluster gauges go? What is meant by “terminal by battery”? I’m trying to finishing wiring my 67 and get it going but I’m lost where this brown/black wire goes from the instrument panel cluster? Do I even need it?

I installed a 5.7 TBI woh a 4L80e tranny in my 67. Any help would be great. Thanks
Posted via Mobile Device

That wire is one of the two wires for the "battery" ammeter gauge. It runs to the black plastic terminal by the battery. You can find more information about it in this post:

https://67-72chevytrucks.com/vboard/...d.php?t=645940

[Gregski]

Originally Posted by dmjlambert

OK, so I searched and figured out nobody has done this before, perhaps nobody was interested other than me. I guess I'm a visual person. I mapped it out.

Switched and dimmed for dash lights means this section has 0 to full current depending on the headlight switch and dimmer position.

Return from fuel level sensor means this is attached to the ground side of the fuel gauge, and the wire that plugs into it supplies ground through the float's variable resistor. This doesn't really belong on a fuse panel, as it is only a connector and has nothing to do with supplying power to anything, but perhaps it was considered convenient.

Always On means this always has battery voltage regardless of position of ignition switch.

Accessory means this has battery voltage in accessory and on positions of ignition switch.

Key On means this has battery voltage in on position of ignition switch, but not in accessory position.

Attachment 1676198

six years later, but I don't care, this is friggen AWESOME, thank you so much for posting it !!! deserves to be seen by more young Padawans that's fer sure