New from Oregon
Thread Starter
4th Gear
Joined: Nov 2025
Posts: 4
Likes: 0
New from Oregon
Hi folks,
First day here so I wanted to say hello. I just purchased a C3 from my father. It’s a 75’ stingray all original w/ 20k miles. The engine runs very well, but there are a few electrical gremlins that will keep me busy. In a way, it’s actually been fun chasing them down and learning about the car through that process. It’s refreshing know there is a “mechanical” logic to the car. If there’s an issue, I know it won’t be related to a computer or control board. Most likely, it will be something I can trace and follow. Anyway, I’m glad this group is here as I am positive I will have tons of questions.
The next thing I’m trying to figure out, is why there is a loud electrical buzzing sound when I turn the gauge lights on? Any pointers would be appreciated, and I’ll post again if I am able to track down the cause later today.
First day here so I wanted to say hello. I just purchased a C3 from my father. It’s a 75’ stingray all original w/ 20k miles. The engine runs very well, but there are a few electrical gremlins that will keep me busy. In a way, it’s actually been fun chasing them down and learning about the car through that process. It’s refreshing know there is a “mechanical” logic to the car. If there’s an issue, I know it won’t be related to a computer or control board. Most likely, it will be something I can trace and follow. Anyway, I’m glad this group is here as I am positive I will have tons of questions.
The next thing I’m trying to figure out, is why there is a loud electrical buzzing sound when I turn the gauge lights on? Any pointers would be appreciated, and I’ll post again if I am able to track down the cause later today.
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From: Northern Illinois
2023 Corvette of the Year Winner - Modified
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St. Jude Donor '18 thru '25
Welcome to the Forum, moving you here to the right folks for some help, good luck
Melting Slicks
Joined: Jul 2006
Posts: 2,292
Likes: 494
From: Salmon Arm, BC
Welcome!! Since it's your Fathers car, I bet you will keep it for a long time. This is the place to be to get the best help for your C3 from Guys who know the car inside and out.
My advise is to get an AIM (Assembly Information Manual) and a factory electrical manual right away....they are extremely helpful when trying to understand how your car works.
My advise is to get an AIM (Assembly Information Manual) and a factory electrical manual right away....they are extremely helpful when trying to understand how your car works.
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,150
Likes: 4,260
From: US-PNW
Welcome! what part of the state are you in?
So the buzzing only happens when you pull the switch **** to the first indent? Silences when you pull all the way for headlights? Does it happen when the key is on and off? Does it sound like it's a true warning buzzer like for the seat belts or such? Can you track down the location of the buzzing noise?
(I don't know where I'm going with this as I'm not familiar with '75s and what's normal -- just trying to better define when the buzzing happens.)
Did '75 have a warning buzzer if the headlight doors don't open all the way or are left on when key is off?
So the buzzing only happens when you pull the switch **** to the first indent? Silences when you pull all the way for headlights? Does it happen when the key is on and off? Does it sound like it's a true warning buzzer like for the seat belts or such? Can you track down the location of the buzzing noise?
(I don't know where I'm going with this as I'm not familiar with '75s and what's normal -- just trying to better define when the buzzing happens.)
Did '75 have a warning buzzer if the headlight doors don't open all the way or are left on when key is off?
Last edited by barkingrats; Nov 2, 2025 at 11:15 AM.
Thread Starter
4th Gear
Joined: Nov 2025
Posts: 4
Likes: 0
Good questions.
So, the buzzing happens at both the first and second indent. It gets louder as I rotate the **** to brighten the gauge lights, and when I turn the gauge lights off, the buzzing stops, even if the headlights are still on. The sound seems to be coming from directly behind the speedometer, but it's hard to tell for sure. It doesn't seem like a normal warning buzzer, but it's almost as loud when I turn the brightness all the way up. It almost sounds like increasing resistance in the electrical circuit somewhere.
So, the buzzing happens at both the first and second indent. It gets louder as I rotate the **** to brighten the gauge lights, and when I turn the gauge lights off, the buzzing stops, even if the headlights are still on. The sound seems to be coming from directly behind the speedometer, but it's hard to tell for sure. It doesn't seem like a normal warning buzzer, but it's almost as loud when I turn the brightness all the way up. It almost sounds like increasing resistance in the electrical circuit somewhere.
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Safety Car
Joined: Oct 2007
Posts: 4,384
Likes: 1,755
From: Seattle Area Washington
Welcome...
I believe in 1975 the Headlight Warning Buzzer was standard equipment...
Your Instrument lighting (Gauges Lighting) brightness passes through the Headlight Switch rheostat and then to the short INST LPS 5amp fuse
The brighter the instrument lighting the more voltage passes through the fuse...
Look at your fuse panel, the very bottom left you may see a Green connector with a Tan wire plugged into the LPS socket...
So it makes sense the more voltage going to Buzzer the louder it sounds, no voltage Buzzer is silent.
Remove the connector and see if the buzzing stops...
I believe in 1975 the Headlight Warning Buzzer was standard equipment...
Your Instrument lighting (Gauges Lighting) brightness passes through the Headlight Switch rheostat and then to the short INST LPS 5amp fuse
The brighter the instrument lighting the more voltage passes through the fuse...
Look at your fuse panel, the very bottom left you may see a Green connector with a Tan wire plugged into the LPS socket...
So it makes sense the more voltage going to Buzzer the louder it sounds, no voltage Buzzer is silent.
Remove the connector and see if the buzzing stops...
Last edited by bmotojoe; Nov 3, 2025 at 08:22 AM.
