73-87 Chevy _ GMC Trucks > Instrumentation

Dash light and other Intermittent issues.

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sgrinavi:
Hi guys, I have an 81 K20 5.7 manual that's giving me a fit regarding the instrument panel.

For starters, I have the dreaded no-gauge light issue - changed the light switch, no help.  Started to follow the guide (here http://forum.73-87chevytrucks.com/smforum/index.php?topic=26558.msg221363#msg221363 ) and found that I don't have power on either side of the inst. fuse but do have it at the dark green wire on the light switch. 

EDIT - I have power on the dark green side of the INST. fuse, but nothing on the "red" side (assuming it's supposed to be gray?)  (See attachment)

Pulled the dash apart and peeled about 30 feet of electrical tape off the harness(s) and found some oddities - (see attached) .  I cleaned  up the connections, but didn't attempt to figure out what they were doing, I'm guessing a radio, but the one that was installed was not hooked up to anything.

The other intermittent issues that may, or may not, be related.   The wipers work sometimes (I changed the switch, no help), the brake light comes on sometimes, the seat belt buzzer/light comes on sometimes.   Directional light indicators always work as all the exterior lighting.  My dome light doesn't work, but I haven't really looked at it.

The ground seems to be good; I've used for testing and it hasn't been flaky.

Questions -

EDIT - Figured out how to split the box. DUH.

I tried to pull the fuse block off the fire wall to see if I had some corrosion on the back side, but can't seem to get it apart, the screws come out and it's loose, but I can't seem to get to the back side of it.  Does it split apart somehow?

Does it sound as though all my issues are related?

Any idea what that random yellow wire is for?

EDIT, The red wire comes from the INST. fuse (opposite the dark green)

Any idea what I need to do to straighten out that red/gray splice?

Mike81K10:
The gray wires is probably your dash lights and the red wire should not be twisted with them. The multiple black wires spliced together is normal and is a factory ground splice.

PS: The two red wires in fuse panel is probably OK, There are a couple places something like that occurs. Take a look at the wiring diagrams supplied on this forum.

sgrinavi:
Thanks for the response.

I've been digging at it some more - The red wire on the back of the fuse block is the one that is twisted with the three gray wires in the previous photo and is opposite the dark green on the INST. fuse.  According to the wiring diagram that should be a gray wire and should terminate at the instrument panel plug

bd:

--- Quote from: sgrinavi on April 10, 2022, 06:30:37 AM ---Hi guys, I have an 81 K20 5.7 manual that's giving me a fit regarding the instrument panel.

EDIT - I have power on the dark green side of the INST. fuse, but nothing on the "red" side (assuming it's supposed to be gray?)  (See attachment)

EDIT, The red wire comes from the INST. fuse (opposite the dark green)

--- End quote ---

You are correct that the red wires from the INST fuse substitute for gray.  The pictured "twisted" splice of red to gray wires is not factory, suggesting that the harness is aftermarket and/or otherwise jury-rigged. 

Burnish the INST fuse contacts in the fuse block.  You can accomplish the task by smearing some fine grit valve grinding compound onto the blades of the old fuse then repeatedly insert and withdraw the fuse.  Rinse the fusebox contacts after burnishing using WD-40, blow the fusebox "dry" using compressed air, and then install a new 5-amp INST fuse.  You may need to burnish other fuse sockets, similarly, to help solve intermittent power delivery issues.  Severe oxidation of blade-type fusebox contacts is not particularly common but can be confounding when it occurs.  In contrast, glass cartridge-type fuse boxes were plagued with oxidation issues.

At least one of the gray wires should route to the I/P cluster connector.  If not, you will need to correct that to establish cluster illumination.

The dangling yellow and black/white wires may have been power and ground for an aftermarket radio and subsequently abandoned.  You will need to trace those wires to determine where they connect.

Mike81K10:
Here is a pic of the fuse block

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