The reason you have no power on the INST Lamp fuse is that this fuse is in series with the dimmer reostat on the headlight switch. It does not get power from the battery or the ignition switch. Your problem is most likely the headlight switch. Don S

 

Fuses

Very few clocks still work in our vehicles a this age. You can try removing the clock and lubricating it with sewing machine oil and see if it starts, if not they can easily be upgraded to a quartz movement. The instrument lamps are your lights for the gauges and speedometer. Did you try inserting a fuse in the slot. It's hard to read but it looks like a 15 amp fuse. That other plug is probably a jumper plug. Whenever anything is plugged into the fuse box it will have another jumper plug to power other options or accessories in case the plug is taken.

Paul

 

thanks for the fast reply! I figured teh clock was just old but my fuel gauge isnt working either. do you think its the same issue, ie its just old? or is it to do with the fuse issue I was describing? I did put a fuse in, its actually 5 amp. Theres no power at that fuse only. Im stumped as to why though.

 

Instrument lamps are wired into the tail lights. So when you back a boat into salt water as I have done on numerous occasions it blows the fuse as you stab the brakes to slide the boat off the trailer unless you first remembered to unplug the trailer (I never have yet); or installed a circuit breaker in place of the fuse that reconnects the circuit once the short is gone.

I deleted your other duplicate post. Only one thread per topic is allowed to help people in the future searching for answers to their problems. The SEARCH function allows you to find answers to frequently asked questions and is indexed by Google so it is a fast accurate search of our archives.

Big Dave

 

sorry about the duplicate post Dave and thanks for the info. however, I still dont understand why all of the other fuses posts are getting powered but this one isnt. the fuse is good, brand new. from what i can tell there is no power going to this part of the fuse box only. HELP please!

 

Just my 2c, but the fuse holder looks like it was burnt at one time and could be the reason why someone added the pigtail to the bat. terminal.
My clock is within the wirering harness and not a seperate lead like yours. The other connector looks like a plug for an aftermarket radio that needs 12V bat. for the clock and memory settings.
As Dave mentioned, the inst. lmps. controlls a few things so if the holder is burnt from the backside this would explain this problem. The good news is that it isn't hard the to pull the fuse panel out, just remove the two hex head bolt's that are diagonal of each other on the corners.

 

thanks 68imp. actually the fuse holder in ALL the terminals were rusty as hell. i cleaned them all out as best i could. they all get power except the INST one. I did unscrew the box but is there a way to replace the fuse holder? Im confused.

 

First, is there power to the wires that go to that fuse holder on the backside?
Yes I think there is a repair for them although I dont know where, try to Google it. If nothing I think you can replace on out of a scrapped fuse box; they are all similar back then. The holder just snaps out and solder the wires back in.

 

Repair

Pretty easy repair if you are a good solderer. They press together in the front and then push out the back. Hopefully it will just be a burned out wire going to one of the connectors.

You can also buy new connectors if you need them:

http://www.lectriclimited.com/repair_components.htm

Paul

 

thanks guys, Im going to check to see if ive got power on the back of the fuse box this weekend. fsc66, what do you mean "they press together in the front?"

 

Connectors

Look at the replacement holders. They have small nibs on the bottom that need to be pushed in with a jewelers screwdriver, so the connectors can push through the back and be released.

Paul

 

Maybe I misunderstood but should'nt all circuits run through a fuse except the battery terms. of course. So what your saying is the headlight switch (a rheostat) dictates how much of the 12V goes through the fuse?

 

Yes, that is the only fuse in the box that doesnt get powered from the battery or ignition switch according to the wiring schematic. Power to the dash lights starts at the headlight switch, goes thru the fuse in the fusebox then to all the dash lights. So, if no 12 volts+ comes out of the headlight reostat, no power will be on the fuse. Look for a dark green wire on the headlight switch. that is the wire that goes to the fuse. Put a test light there, if no power is on that wire when you pull out the switch to turn the headlights on and rotate the dimmer then the switch is bad. Don S

 

Might add that the rheostat in the light switch has often proven defective (it is a very fine wire wrapped around an asbestos board and the wire often breaks from wear). The only fix is a replacement light switch if the dimmer is bad.

Big Dave

 

thanks guys! this is SO helpful, Im going to check that tonight. I DO have headlights when i pull the switch out but definitely no dash lights and no dimming either (obviously). Is it possible that the switch works to turn the headlights on but not engage the instrument lights? or would i not have headlights too?

 

thanks Don S. ! since you must have a wiring schematic could you please tell me the best place to get one of my own?

 

The 68 full size assembly manual has a section with all the schematics. Also, you can get a 10 page or so book from either Classic Ind or Year One titled "1968 Chevrolet wiring diagrams for complete chassis".
You definately can have headlights work but not the dash lights because the power comes out of a different terminal. As Dave stated the wire-wound reostat is probably broken on the switch.

 

Switch

New headlight switches can be found all over eBay, both new and OEM.

Paul

 

I think I might have to take a trip to the electrical section of my book....I like to hang out in the mechanical part of it. Thanks Don.

 

PROBLEM SOLVED!! it was the switch. got a replacement at autozone for 14 bucks and Im back in business. I would NEVER have thought to replace the switch since the headlights were working. THANK YOU SO MUCH! this place is great! Im so appreciative of all the help and suggestions everyone gives. you guys rock!