Dash/Gauge Lights 1975
Thread Starter
Cruising
Joined: Oct 2009
Posts: 14
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Dash/Gauge Lights 1975
Sorry if this has been asked and answered but I've searched my way through numerous threads and not putting 2 and 2 together ..
Bulbs are good .. fuses are good .. new headlight switch installed ..
Turn indicators work .. warning lights work (brake/lights, etc)
No dash/gauge lights
I'm very capable of following a good set of instructions but need the "Corvette wiring for dummies" approach.
From reading other threads I get the impression I may have a ground issue. No idea where to look, which wire(s), etc. The entire dash is disassembled, wires all hanging loose. The majority of the wiring is gathered together and wrapped up tight in electrical tape (this the factory spec?)
I thought I also read that I can troubleshoot individual lights by grounding them somehow? Read so much it all kinda runs together.
Thanks in advance for all assistance
Bulbs are good .. fuses are good .. new headlight switch installed ..
Turn indicators work .. warning lights work (brake/lights, etc)
No dash/gauge lights
I'm very capable of following a good set of instructions but need the "Corvette wiring for dummies" approach.
From reading other threads I get the impression I may have a ground issue. No idea where to look, which wire(s), etc. The entire dash is disassembled, wires all hanging loose. The majority of the wiring is gathered together and wrapped up tight in electrical tape (this the factory spec?)
I thought I also read that I can troubleshoot individual lights by grounding them somehow? Read so much it all kinda runs together.
Thanks in advance for all assistance
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
INST LTS fuse good? And the headlight switch is turned all the way clockwise stopped just before the courtesy lights come on? (No dissing here, it's happened a lot!)
The dash lights are 95% on a single gray wire and need to be grounded- the grounds come in different form depending on what year and where they (each light) is located.
The dash lights are 95% on a single gray wire and need to be grounded- the grounds come in different form depending on what year and where they (each light) is located.
Thread Starter
Cruising
Joined: Oct 2009
Posts: 14
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I'm totally new to this kind of work .. how?
I have a test light and I have a multimeter.
What do I connect where and what do I touch to what? What do the settings need to be on the multimeter to check what?
Battery connected or disconnected?
I have a test light and I have a multimeter.
What do I connect where and what do I touch to what? What do the settings need to be on the multimeter to check what?
Battery connected or disconnected?
Thread Starter
Cruising
Joined: Oct 2009
Posts: 14
Likes: 0
This is a little (or a lot) frustrating.
To be sure what I'm after .. I believe the INST fuse is at the bottom of the box .. shortest fuse in the box .. next to that is a tab that looks like if should have something plugged on it. It doesn't. And I'm not seeing any wires under there that look like they should plug in there.
With the fuse pulled I touched the test light probe to the holder on both sides and got nothing. How can I test my test light to be sure its good to start with?
Eh .. ignition switched on or off for all this testing?
Here's a pic of what I'm looking at
http://www.wood-pile.com/rk/DSCN0608.JPG
To be sure what I'm after .. I believe the INST fuse is at the bottom of the box .. shortest fuse in the box .. next to that is a tab that looks like if should have something plugged on it. It doesn't. And I'm not seeing any wires under there that look like they should plug in there.
With the fuse pulled I touched the test light probe to the holder on both sides and got nothing. How can I test my test light to be sure its good to start with?
Eh .. ignition switched on or off for all this testing?
Here's a pic of what I'm looking at
http://www.wood-pile.com/rk/DSCN0608.JPG
Last edited by ga1975; Jun 19, 2010 at 11:54 AM. Reason: added image
Melting Slicks
Joined: Feb 2007
Posts: 2,709
Likes: 269
From: S.E. MI
St. Jude Donor '15
The tab next to the inst fuse is not supposed to have anything on it.
The clk ltr ctsy fuse should have power all the time so you can check
your test light there. The tail fuse should have power on both sides
with the headlight switch pulled. The inst fuse should also have
power on both sides as long as the dimmer is rotated ccw with
the light switch pulled.
You don't have to turn on the key for these tests.
The clk ltr ctsy fuse should have power all the time so you can check
your test light there. The tail fuse should have power on both sides
with the headlight switch pulled. The inst fuse should also have
power on both sides as long as the dimmer is rotated ccw with
the light switch pulled.
You don't have to turn on the key for these tests.
Thread Starter
Cruising
Joined: Oct 2009
Posts: 14
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I'm sorry to say I'm not getting it. I have touched the test light proble to a few other things and while the light doesn't come on there is some sparking with the fuses in.
So, should the INST fuse be in or out? Am I probing the end of the fuse while its in? Take the fuse out and probe the holder?
Complete noob I know, but I should be able to get there from here.
So, should the INST fuse be in or out? Am I probing the end of the fuse while its in? Take the fuse out and probe the holder?
Complete noob I know, but I should be able to get there from here.
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Thread Starter
Cruising
Joined: Oct 2009
Posts: 14
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Having never done this type of thing before I lack a good visual of the expected results. I know it seems as simple as clip the alligator to a ground touch probe to something and either get a light or not.
With the battery connected I located the CLK LTR CTSY fuse .. clipped the clip touched the probe to one side of the fuse and got sparks.
Of course adding to the frustration level is the location of the fuse box. My knees and back should be runied either before or after I get this accomplished.
I really do appreciate the time everybody is taking trying to get me through this.
With the battery connected I located the CLK LTR CTSY fuse .. clipped the clip touched the probe to one side of the fuse and got sparks.
Of course adding to the frustration level is the location of the fuse box. My knees and back should be runied either before or after I get this accomplished.
I really do appreciate the time everybody is taking trying to get me through this.
Thread Starter
Cruising
Joined: Oct 2009
Posts: 14
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Maybe having good equipment helps. After buying another test light we have a little success. I tested the test light by connecting it to the battery terminals. Got a nice glow.
Ok .. battery connected, fuse out, light switch pulled out, turned fully counter clockwise got a nice glow from the test light on the right side.
Fuse in I get a glow from the left side.
Ok .. battery connected, fuse out, light switch pulled out, turned fully counter clockwise got a nice glow from the test light on the right side.
Fuse in I get a glow from the left side.
2nd Gear
Joined: Nov 2013
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Maybe having good equipment helps. After buying another test light we have a little success. I tested the test light by connecting it to the battery terminals. Got a nice glow.
Ok .. battery connected, fuse out, light switch pulled out, turned fully counter clockwise got a nice glow from the test light on the right side.
Fuse in I get a glow from the left side.
Ok .. battery connected, fuse out, light switch pulled out, turned fully counter clockwise got a nice glow from the test light on the right side.
Fuse in I get a glow from the left side.
Ga1975- I am having the same problem you detailed. No dash lights on my 1975.... I've replaced fuses/bulbs, ran all the traps, no luck. Did you ever figure out what the problem is with yours?
Thread Starter
Cruising
Joined: Oct 2009
Posts: 14
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When all was said and done I replace the headlight switch with a brand new one and my problem was solved. Once I did that everybody lit up.
Le Mans Master
Joined: Aug 2006
Posts: 7,427
Likes: 1,560
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Center gauge cluster ground is called harness ground.
Double check the fuse as ***Roger*** suggests.
The ground for the center gauges goes from the black wire in the center of your temp gauge to the "A" pillar, it attaches on the left just above the bottom of the dash.
Or you can run a temporary ground to the center bezel.
Still no lights? Then by pass the headlight rheostat by Jumping from the courtesy fuse to the inst fuse, in the bulbs light then the rheostat is bad.
8th Gear
Joined: Aug 2020
Posts: 8
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So after seeing this thread I am willing to try that rheostat test but after I test it and IF the case is that the rheostat is bad then
is there a way to fix the rheostat?
Le Mans Master
Joined: Aug 2006
Posts: 7,427
Likes: 1,560
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Hi and welcome!
I'm having the same problem and have tested the bulbs: they work. Have tested the voltage in one of the bulb sockets: got nothing.
So after seeing this thread I am willing to try that rheostat test but after I test it and IF the case is that the rheostat is bad then
is there a way to fix the rheostat?
So after seeing this thread I am willing to try that rheostat test but after I test it and IF the case is that the rheostat is bad then
is there a way to fix the rheostat?
If the rheostat is bad you can buy a new light switch from Willcox-Corvette.
8th Gear
Joined: Aug 2020
Posts: 8
Likes: 2
Thank you for the reply Peterbuilt!
And just so I understand how the system works:
Once the headlight switch/**** is pulled outwards (to turn on the headlights) the cluster lights, the speedometer, and tachometer lights should turn on? Also, do you twist the headlight switch/**** to brighten the interior instrument lights or the headlights?
Lastly, the directions to twist the headlight switch/**** is counterclockwise: dimming the lights and clockwise: brighten the lights?
Thank you very much for this thread and for the help!
And just so I understand how the system works:
Once the headlight switch/**** is pulled outwards (to turn on the headlights) the cluster lights, the speedometer, and tachometer lights should turn on? Also, do you twist the headlight switch/**** to brighten the interior instrument lights or the headlights?
Lastly, the directions to twist the headlight switch/**** is counterclockwise: dimming the lights and clockwise: brighten the lights?
Thank you very much for this thread and for the help!
Le Mans Master
Joined: Aug 2006
Posts: 7,427
Likes: 1,560
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
The headlight switch:
When you pull the switch OUT to the first click it turns on the parking lights the side markers and all the instrument lights.
Pulling the switch OUT to the second click raises and turns on the headlights, all the previously mentioned lights are ON also.
Dimming the dash lights:
Turning the switch fully clockwise dims the lights.
Turning the switch counterclockwise makes the lights brighter.
Turning the switch FULLY counterclockwise past the 'detent' turns on the courtesy lights.
If all your lights work except the dash lights then the rheostat may be bad.
The jumper test bypasses the rheostat and proves that the rheostat is bad.
It's a lot easier to test first instead of guessing and changing the light switch.
Is that what you are asking?
When you pull the switch OUT to the first click it turns on the parking lights the side markers and all the instrument lights.
Pulling the switch OUT to the second click raises and turns on the headlights, all the previously mentioned lights are ON also.
Dimming the dash lights:
Turning the switch fully clockwise dims the lights.
Turning the switch counterclockwise makes the lights brighter.
Turning the switch FULLY counterclockwise past the 'detent' turns on the courtesy lights.
If all your lights work except the dash lights then the rheostat may be bad.
The jumper test bypasses the rheostat and proves that the rheostat is bad.
It's a lot easier to test first instead of guessing and changing the light switch.
Is that what you are asking?